INTRODUCTION

Keeping with advances in technological medicines; technology is now become an inseparable part of intensive care and emergency medicine¹.

Although history and clinical examination form the key of emergency medicine, newer of newest early diagnostic and therapeutic devices had kept medicine and technology a step ahead of past in emergency medicine and better patient care².

With advancing medicine and technology, different instruments were devised and have become routine in pediatric emergency and intensive care. The instruments like thermometer, sphygmomanometer and weighing machine are in part integral hand of emergency pediatric assessment.

The next era of medicine turned these instruments into electronics, with automated servo-control monitors and the alarms for the abnormal results.

To whatever extent the technology has advanced , its reliability had always remained a question, owing to it’s technical and mechanical errors. Despite these minor shortcomings, these advances still have a valuable role.

Simple clinical signs including respiratory rate, presence of chest retractions or nasal flaring, grunting, cyanosis, pallor and general appearance are used to assess the cardiorespiratory status of infants and children, so also are available many clinical scores.

Investigators have found that although these clinical signs are frequently present, their absence does not reliably exclude the possibility of serious cardiopulmonary disease or lower respiratory tract infections^5,6.

Data from different studies indicate that more than 70% of patients presenting to emergency department have affection of respiratory system and cardiovascular system². Mild to moderate hypoxia is found to be associated with even slightest cardiopulmonary decompensation, when no clinical signs are manifest⁴.

Most healthy individuals exposed to moderate hypoxia will not have a significant increase in their ventilation. Most of initial responses to hypoxia are manifest by increasing tidal volume and peak flow while keeping respiratory rate constant, which rises as a late response to severe hypoxemia⁷.

Pulse oximetry has been advocated as an accurate simple and noninvasive continuous and reliable method of measuring arterial oxygen saturation. It can accurately measure normal SaO₂ and reliably detect clinically unexpected desaturation under a variety of conditions, it may improve our ability to assess the cardiorespiratory status of body tissues and infants and children as a whole.⁸.

Recent technical advances have enabled production of inexpensive and portable oximeters that make routine assessment and oximetry screening possible at reasonable costs.

Reliability and simplicity of pulse oximetry have led some to promote its use as a fifth vital sign⁸.

However, careful studies are required to delineate the benefits and pitfalls of pulse oximetry screening before this technology can be used on routine basis in pediatric practice.

Snow et al. deplored the separation of intellectual life into two cultures: Sciences and humanities: Unable to communicate with each other⁹.

In emergency pediatrics, the two culture metaphors translate loosely into technology versus medical intelligence. Robert Pirsig traced the Snow’s dichotomy back to Plato stating that ‘Maintenance of metaphoric motorcycle requires of its user the thorough knowledge of its mechanism and limitation and a resolute determination to use one’s skills, combining Socratic science¹⁰ – Medical Intelligence and Technology with emphasis on quality in healing arts: that is the goal !

This study was conducted to examine the use of routine pulse oximetry screening of children presenting to Emergency Pediatric Care Unit, to judge the seventy of disease states, to test its accuracy and reliability as the fifth vital parameter.

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ASSESSMENT OF A SICK CHILD

Introduction

. Identifying the acutely ill child with a serious illness is accomplished by careful observation, history taking, physical examination, appreciation of age and body temperature and other parameters as risk factors and judicious use of screening laboratory tests.

History taking and observational assessment is to be continued as the physical examination is performed simultaneously. Observation is the key factor in evaluation of children with acute serious illness.

Accurate emergency assessment of the patient or a sick child presenting to emergency or casualty is the key in detecting the seventy of illness and risk to vitality of life and body systems.

In contrast to adult medicine, 60 to 70% of sick children presenting to emergency units will not have a serious or life threatening illness, but if overlooked 10-20% of the sick children presenting to emergency unit may have serious / acute illness which may be missed clinically².

Therefore it needs careful evaluation of children presenting to emergency department to detect early the severity of disease.

Advances have been made in rapid investigations and therapeutic interventions in modern medicine, but history taking and general assessment of the sick child still forms the basics of diagnosis.

There can be no single tool which can replace clinical emergency assessment, newer devices can only assist the same.

Emergency assessment of sick child

As a patient presenting to emergency unit may present with any of the infinite number of possibilities of derangement of vital organs systems, the accuracy and speed in detecting life threatening and potential life threatening conditions through rapid clinical assessment assists physicians in making provisional diagnosis and treating the patient earliest with best possible interventions and therapies.

A representive assessment of each vital system or organs {viz: respiratory, cardiovascular, neurological system etc.} is important, to anticipate potential life threatening illnesses at least on a broader scale. As the child can present with any of the clinical presentations, sorting out critically ill children and children requiring intensive interventions needs to be done, in the emergency system, at the earliest possible time.

Methods of assessment of vital systems :

Depending on different presentations, different methods of clinical assessment are described :

1. Traditional methods of General and Systemic Special Examination

2. Acute illness observation scales¹²

3. Signs and symptoms specific scales

4. And specialised scales for different diseases:

· Clinical Asthma Score¹³

· Westley croup score¹¹

· Glasgow Coma Score¹¹

· Pain scales CRIES , CHEOPS scores¹²

· McCarthy Scale¹²

Limitations of modified clinical assessment scales :

1. Most of these scales are specailised for specific system derangement e.g. GCS, Asthma score, telling less about other systems.

2. Multisystem derangements can give false scores.

3. Many parameters, so may be cumbersome to remember and to calculate.

4. Can never replace complete clinical examination

Traditional Methods of Assessment of Sick child

Clinicians or best called as the diagnosticians in pediatric out patient care unit and pediatric emergency care unit need to know all possible life threatening conditions and such potential conditions in any sick child presenting to a emergency unit ..

Inferring from short and adequate but rapid clinical history and early and complete examination of different vital parameters and examining specifically for clinical signs / symptoms of potential life threatening illness, which help the pediatrician in sorting out relatively ‘stable’ cases from ‘sick children’ – who require early intervention and hospital based care or referral to a higher specially or intensive care unit. So a thorough general examination of child was advisable with respect to following parameters :

1. General Appearance - Normal / Sick / Very sick

2. Vital parameters

· Temperature

· Respiration

· Pulse

· Blood pressure

· Weight

3. Potential life threatening signs:

· Pallor

· Cyanosis / clubbing

· Edema

· Icterus

· High / Low JVP

· Capillary Refill time

· Bleeding tendencies

· Lethargy and altered sensorium etc.

General Appearance

Thus a sick child according to parents can be any child who is not normal / not behaving normal or has some abnormal symptom or sign – it can be any thing from fever, lethargy, excessive crying refusal to feeds to severe sepsis, bleeding tendencies, unresponsiveness. So a sick child although means need for therapeutic intervention, does not always mean a serious illness or a potential life threatening situation. The term very sick child although is more subjective, is usually associated with high chance of potential life threatening illness. It’s the pediatrician who on further examination decides regarding the need for early intervention and hospital based treatment².

Vital Parameters

Normal functioning of different body functions depends on the state of vitality of different organs and systems. Thus there are vital organs namely heart, lungs, brain and accessory vital organs namely liver, kidneys, adrenals etc. Also there are vital systems – related to physiology of vital organs – namely cardiovascular system, respiratory system, nervous system and other systems like alimentary, excretory, reticuloendothelial system.

Age old knowledge of vital organs made to device few clinical parameters as representative parameters or representative vital parameters mainly –Temperature,Pulse ,Respiration,Blood pressure…etc.

Also modern clinicians and pediatricians have deviced accessory vital parameters which are the potential life threatening signs as mentioned above.

Medical advances have developed in devicing novel methods to detect derangements in vital systems the earliest viz: Non invasive Blood Pressure measurement devices, Transcutaneus oximeters,expiratory air capnometers, and pulse oximeters. So, advances have been made to detect derangement of O₂ and CO₂ at intravascular / capillary / tissue level before it manifests clinically, by oximetry and capnometry. Capnography can provide early warning to potential life threatening problems, but such problems often result in desaturation. NIBP also is an important and reliable mode of assessing circulatory status but changes in blood pressure are seen very late, compared to other vital parameters.

Bedside monitoring of more complex variables is now feasible. However, it is important to remember that a monitored variable cannot replace and should be used in conjunction with careful and repeated physical examinations and bedside evaluation of patient¹⁴.

Some have suggested pain, weight, noninvasive blood pressure and smoking status of family members as an important vital parameter².

Temperature : Normal body temperature is maintained by exchanging heat at periphery mainly through skin through its arteriolar and various capillary network, with the air.

Thus assessment of temperature can help in assessing :

1. Basal Metabolic Rate.

2. Adequacy of circulation.

3. Temperature can be the only distinguishing marker for diagnosing – sepsis, pontine hemorrhages etc.

4. Comparative assessment of peripheral (axillary) and central (rectal temperatures) may help in early diagnosis of disease state.

Pulse : The main vital parameter which makes the tissue and organs and also other vital organs ‘live’,by supplying them the adequate requirement of oxygen and energy to maintain health and fight illnesses. It’s a peripheral manifestation of cardiac activity. There are people and whole system of Ayurveda, who can diagnose different illnesses by just feeling for pulse. Apart from cardiac function, pulse also determines the peripheral resistance. The different parameters of pulse viz. Rate, Rhythm, Volume, Tension etc help in early detection of potential cardiovascular illnesses which other wise remain undetected.

Blood Pressure : Another important parameter for assessment of cardiovascular system and the systemic circulation is blood pressure. It mainly estimates peripheral resistance and the cardiac output which are the two main things which get decompensated in severe illness. Not only hypertension, but hypotension is also equally significant marker of detecting early derangement in cardiovascular system. Maintenance of normal blood pressure although suggests normal cardiac function and peripheral perfusion of oxygen and nutrients in early stages of illness, body’s compensatory autoregulatory mechanisms can maintain normal blood pressure, and the underlying disease state or early potential life threatening state may be overlooked.

Respiration : It is probably the most important vital parameter in pediatric medicine. Further most of other pediatric admissions and intensive care admissions have secondary affection of respiratory system by derangement of neuro metabolic system.

Assessment of Respiratory System

Since ages, respiratory system is considered as the chief vital system. Every tissue requires oxygen; oxygen is known as the ‘Life Gas’. Every cell / organ / system, requires oxygen for its survival and normal and productive functioning and thus for the vitality of life.

Thus oxygen forms the sole ‘Soul’ of life and thus of its all vital parameters.

This O₂ demand of tissues and vital organs is met mainly by respiratory system its favorable anatomy and physiological drive to confirm respiration constantly supplying ‘life’ to each tissue and vital organ with the assistance of cardiovascular system. Oxygen which is exchanged with air at the alveolar level, for the CO₂ produced as a tissue metabolite; is carried to heart through pulmonary circulation from which it is pumped to different organs and tissues through cardiac output for their adequate survival and function and thus for cellular or peripheral respiration. Also it provides life to cardiac contractility, brilliance to brain's CNS regulation and also for functioning of various enzymes that lit the fire of vital chemical reactions in body.

Thus slightest derangement in oxygenation of tissues and organs may affect their functioning significantly, although not obvious even with detailed general and systemic examination¹⁵. Also, derangement of other vital organs and system will easily affect oxygen transport and thus peripheral oxygenation.

To summarize, oxygen is the vital parameter of body.

Traditional vital parameter -- Respiratory Rate :

One of the earliest clinical signs which is used by people since days of ancient medicine, to judge the presence of life is chest movement, or more scientifically called as 'respiratory rate' is easy and has good accuracy¹⁶. Serial measurements of respiratory rate is easy and has good accuracy. Slightest derangement of body metabolism manifesting as hypoxia / hypercapnea and other neurometabolic disturbances will result in compensatory and later decompensatory alternations of respiratory rate and rhythm, which if picked up earliest will save time required for early intervention in emergency pediatric medicine.

RESPIRATORY MONITORING

Many of the recent improvement in monitoring of critically ill children in Intensive Care Units and Emergency Care Units have been in area of hemodynamic monitoring. Ability to monitor variable related to respiratory function may be even more important because patients with respiratory distress constitute large proportion of critically ill patients including all patients with potentially serious respiratory dysfunction. Respiratory monitoring should serve as an indicator of illness severity at one point in time as well as provide serial measure of changes in the same⁴.

Goal of any monitoring system is to^16,2 :

(1) aid in diagnosis (2) guide and assess therapy (3) alert caregivers

to change status and detect complications.

``Respiratory Monitoring^2,16

Physical Examination		Ø Tachypnea Ø Retractions SSR(suprasternal retractions) SCR(subcostal retractionsI ICR(intercostal retractions)
		Ø Alae Nasae flaring Ø AE Ø Foreign sounds
O₂ level		ABG (Arterial blood oxygen saturation) SaO₂PaO2 Ø Transcutaneus O₂saturation Ø Noninvasive pulse oximetry Ø Mixed venous O₂ saturation
CO₂ level		Ø ABG --PaCO₂ Ø Tc CO₂ Ø Capnography
Respiratory drive		Ø P_0.1 _ØV_t / T_i
Respiratory muscle strength		Ø Pi max ; P_E max ,
Respiratory muscle endurance
Respiratory mechanics	Ø VC (vital capacity ) Ø FRC(functional residual capacity) Ø Compliance

Respiratory monitoring may indicate :

1. Acute need for therapy to treat and prevent respiratory failure.

2. Progression of illness despite therapy.

3. An improvement related to therapeutic intervention

4. Ability to maintain spontaneous ventilation

5. Unfortunate irreversible loss of respiratory function.

Limitations of traditional methods of assessment :

1. A normal clinical examination cannot rule out a potential life threatening hypoxia, in pediatric medicine.

2. As the examination takes time, has different variables each requiring an instrument or a time lag which may delay the diagnosis.

3. Clinical complex examination may not be accurately possible in life threatening illnesses, when resuscitation needs a simultaneous attention.

4. Accessory vital parameters / disease signs may be overlooked in emergency set up.

Efforts have always been made to detect derangement of vital parameters earliest, before any of the clinical signs are frequently present, but their absence does not rule out or reliably exclude the possibility of serious cardiopulmonary disease or lower respiratory tract infection. Several clinical studies demonstrate that fall in arterial oxygen saturation most often precedes any changes in vital signs.

Devices aiding in clinical assessment

As respiratory system is main vital system as discussed above ,techniques to measure respiratory function were devised ; for example : arterial blood gas, capnometry, spirometry, pulse oximetry etc.

Arterial blood gas analysis :Important, reliable, gold standard initial investigation in a sick child to determine abnormal oxygenation, ventilation, perfusion. Also it gives idea about blood PH. Although it is invasive and continuous monitoring of oxygen saturation is difficult and not without hazards, it is still a valuable tool in managing sick children and keeping a check on modern machines.

End tidal carbon dioxide concentration :It is simple noninvasine method to measure exhaled carbon dioxide which in turn gives idea about alveolar carbon dioxide concentration and thus ventilatory status .It is easy to use and accurate but costly. Also hypercapnoea is a late manifestation of any disease as compared with hypoxia. It serves as an important tool to assess ventilatory status in intensive pediatrics along with pulse oximetry.

Spirometry: This is an useful tool to accurately assess respiratory function by using physiological methods. Its main use is in older children and mainly for neuromuscular diseases. It's not much useful in acute condition and emergency assessments for use in sick children due to it's cumbersome method.

Transcutaneus oximetry :,A newer noninvasive method of analysing mixed venous oxygen saturation is transcutaneus oximetry.Its main problem is that it has to be frequently calibrated and needs a lot of consumables and hence has been replaced by pulse oximetry.

In the course of time pulse oximetry has come up as a simple ,easy, accurate, reliable ,portable and affordable method of capillary oxygen saturation analysis .

OXIMETRY

Oxygen is the vitality of life, hence a parameter to judge oxygenation will be higher in it’s importance as far as emergency assessment is considered. Ability of respiratory system to contribute oxygen to blood is important in maintenance of normal cellular respiration and organ functions. Peripheral oxygen delivery[VO2] is the product of cardiac output [CaO2] and arterial oxygen content[Q4]. .

VO₂ = Q₄ X CaO₂

Arterial oxygen content is determined by saturation of Hb and O₂ dissolved in plasma.

Q = [Hb X SaO₂ X 1.34] + [PaO₂ X 0.003]

So ability to monitor PaO₂ and SaO₂ is a key reflection of cellular respiration.

Method of assessment of peripheral oxygenation is called as ‘oximetry’¹⁷.

HISTORICAL ASPECTS : Oximetry¹⁷

1851	Von Gerlach an instructor at Royal Veternesisass school, Berlin, observed exchange of O₂ and CO₂ across skin and suggested that it is dependent an quantity of blood streaming through capillaries and its flow velocity¹⁸
1951	Baumgarder and Goodfriend reported PaO₂ measurement in humans through intact skin by immersing a finger in PO₄ buffer.
1956	Leland and Clarke presented polarographic O₂ electrode, for PO₂ measurements.
1957	Proth et al confirmed Clarke’s methods
1969	Huch et al reported PO₂ values equal to arterial values obtained with PO₂ electrode placed in skin surface made hyperemic by topical drugs.

Oxymeters¹⁷

	1934	Kramer deviced first oximetry using single Wavelength light¹⁹
	1935	Carl Mathes built the first device that continuously measured human blood O₂ saturation by transilluminating tissues in vivo, using 2 wavelengths of light one sensitive to oxygen and other not. J. R. Squires, Britain – deviced a similar instrument that was calibrated by compressing the tissue to elliminate blood²⁰.
	1940	The term oximeter was coined by Glen Millikan to describe light weight device, he developed in aviation research – which was a photoelectric instrument for measuring continuously the O₂ saturation of arterial blood in mass without puncturing the vessels²¹.
1942		Was the milestone of progress with Millikans’s ear oximeter .
1950		Eontwood deviced Wood oximeter, double scale instrument with separate measurement of absorption of infrared and red wavelengths
1970		Hewlett Packard marketted first self calibrated can oximeter using 8 wavelengths of light.

Oximetry thus refers to group of methods even gasometric for determining the O₂ saturation of blood generally in vitro as well as in vivo.

In following decades several laboratories attempted to improve measurements by producing devices such as oxyhemoglobinograph and oxyhemograph and anoxia photometer.

Principle : Beer Lambert Law^1,22,23

Light has the ability, not only to be reflected, absorbed or transmitted through a substance but also be refracted or bent as it travels through the medium. But its frequency remains constant so its wavelength must change.

C speed in vacuum

Refractive index =

V Speed in medium

Ist part of B-L Law : When a parallel beam of light falls on a semitransparent homogeneous substance, intensity of transmitted light decreases exponentially as distance through the substance increase

It = Intensity of transmitted high

It = Intensity of incident light

d = distance the light has traversed

IInd Part of B-L Law : If a parallel beam of light is transmitted a known distance through a clear solution with a dissolved solute, the intensity of transmitted light decreases exponentially as concentration of solute increases.

Combining two laws : Laboratory oximeters transmit 4 or more wavelengths through a cuvette filled with a solution of lysed RBCS. The point at which extinction coefficient equals for different Hbs viz Hb and HbO₂, is called isoelectric point i.e. 805nm for Hb and HbO₂ same is extrapolated for pulse oximetry.

Principles and physics^1,22,23

Noninvasive oximeters measure red and infrared light transmitted through a tissue bed effectively using finger or ear lobe as cuvette containing hemoglobin.

Technical problem : Many absorbers in light path, other than Hb viz : skin, soft tissue. Capillary blood.and four different Hb species

Physics^23,24 : Pulse oximeters deal with the effects of tissue and venous blood absorbencies in a completely different way.

AC : at the top of tissue bed is pulsatile or AC component which is attributed to pulsatile arterial blood.

DC : Baseline component represents absorption of tissue bed, including venous, capillary and nonpulsatile arterial blood pulsatile expansion of arteriolar blood / bed increases path length, increasing the absorbance.

All pulse oximeters assumes that the only pulsatile absorbance between the light source and photodetector, is the arterial blood. They use two wavelengths of light ; 660nm (Red) and 940(nm) (non infrared). Pulse oximeter first determines the AC component of absorbance at each wavelength and divides this by corresponding DC component to obtain a ‘pulseadded’ absorbencies that is independent of incident light intensity.

It then calculate the ratio (R) of these pulse added absorbencies which is empirically related to SaO₂.

AC 660 / DC 660

R =

AC 940 / DC 940

Thus when the ratio of red - infrared absorbance is 1, the saturation is approximately 85%.

Technical problems :

1. Dyshemoglohbins and dyes : These cause large pulsable absorbance at both waveingths. Eg. (a)CO Hb – at 660nm it appears as O₂Hb and thus it will give falciously high readings of SPO₂ compared to SaO₂.(b).Meth Hb – at 660nm it has absorbance equal to Hb and at 940 nm it has high absorbance. As meth Hb level increases SPO2 tends towards 85% thus giving falaciously high and low valves independent of SaO2,(c)Hb F - Atthough constitutes a small but variable fraction of Hb in neonate, O2HbF partly behaves as CoHb. (d)Intravenous dyes - by changing the absorbance, definitely will alter the SPO₂ values.

2) Light Emitting Diode [LED] center wavelength variability : This can be avoided at manufacturer level by rejecting LEDs in out of range, alternatively pulse oximeter can be programmed to accepted several ranges of LED wavelengths for both red and infrared light allowing the device to correct internally.

3) Managing Signal Artefact: It’s the most difficult engineering problem, to identify the ‘ripple’ absorbance pattern of the arterial blood in a ‘sea’ of electromagnetic artefacts. Three major sources of artefact are known

a) Ambient light b) Low perform c) Motion .

a) Ambient Light : oximeter attempts to eliminate light interference pattern even in a quickly changing background of room light, by sequentially turning of one, other and both LED lights in fraction of seconds. This can be minimised by covering sensor with opaque shield.

b) Low Perfusion and Signal noise ratio : Small pulsatile absorbance signal because of low perfusion leads to low AC/DC ratio and oximeter amplifies the signal and estimates SPO₂, it can be minimised by setting minimal values for signal / noise ratio below which oximeter displays no SPO₂^.

c) Motion Artfacts : Patient motion with large AC/DC signal can make oximetry useless. The effect can be lessened by averaging the device over a longer period. Artefact rejection scheme can be set up in an oximeter.

Accuracy and response : From various methods comparison studies, it is found that SPO₂, value is as accurate as empirical collaboration curve, although there can be specified uncertainly of ±2% or 3SD it can be 2 to 3 times large.

Other Limitations of Pulse Oximetry: Arterial O₂ saturation is only a portion of the information needed to monitor the adequacy of tissue oxygenation. Delivery of O₂, to tissues is also determined by Hb, CO & O₂, affinity for Hb. Saturation readings are also a relatively insensitive guide to adequacy of alveolar ventilation and O₂, transfer by lungs.

USES OF PULSE OXIMETRY^1,14,23,24

I. Emergency Pediatrics

· In Triage Department for differentiating seriously ill children for referal to emergency unit ,especially in cases of trauma

· Early detection of hypoxia in emergency units in cases of lower respiratory tract infections and potential respiratory failures as in Guillian Barrie Syndrome for early detection of respiratory decompensation

· Emergency monitoring in life saving intervention & cardiopulmonary resuscitation.

II. Intensive pediatrics

· Monitoring to assess effects of treatment / changes as ventilatory settings, inspired O₂ concentration and CPR.

v Neonatal care units :

· Ascertain transient fluctuations in PaO₂ in infants & neonates especially apneic prematures.

· Unstable infants, septic neonates, extreme low birthweight neonates

v Intraoperative & postoperative monitoring:

· Preanesthesia, during the surgery or anesthesia & mainly postoperative monitoring.

· Pre and post procedural monitoring of children : e.g. for bronchoscopy

· In post operative anaesthesia care units for detecting potential cardovascular decompensation the earliest

III. Ambulatory Pediatrics

· Transport of unstable infants from primary care units to higher centers

· Also for use of community health workers as a decompensation survellance tool

· In transport medicine as in EMS squads while transporting patients from place of event to hospital set up

IV. Under research¹

· Plethysmographic use to determine blood pressure by studying the reappearance of waveforms

· To determine adequacy of peripheral perfusion.

· Patency of ductus arterosus.

· Level of ischemia in peripheral vascular diseases.

· Patency of arterial grafts.

· Bowel viability testing intraoperatively to determine site of resection of bowel.

· Fracture manipulation for early detection of vasular compromise.

As pulse oximeter measures oxygen saturation accurately, it has a direct association with any cardiorespiratory disorders.It may pick up changes in oxygenation beforehand of appearance of any clinical abnormality or sign.Hence it would be a very important parameter to aid in management of a sick child along with traditional vital parameters like temperature, pulse, respiratory rate and blood pressure.

PULSE OXIMETER Photographs – Oximeter Probe design

REVIEW OF LITERATURE

The advantage of pulse oximetry is that it is easily applied and has a much more robust probe than transcutaneous monitors, and is noninvasive.

However it must be remembered that it is the indicator of percentage saturation of capillary blood & not the partial pressure of dissolved O₂ in the blood. Although they are related by O₂ dissociation curve, it is changed by a number of variables.

Safety and accurrance in the use of pulse oximetry depends on knowledge of the limitations of technique as discussed before.

Above features of oximetry made them to get included in protocols for emergency and intensive care units for their routine use. According to the hospital protocol SPO2 < 93 % suggests significant respiratory compromise .

PULSE OXIMETRY AND EMERGENCY MEDICINE :

Due to it's reliability and accuracy pulse oximetry usage had been changing from post operative and intensive care units to emergency units. It has made people to use it as a routine triage investigation to sort out cases with significant hypoxemia from less critical cases and also determining need for extended observation and treatment .

Shoemaker WC, Wo CC, Chan L, Ramicobne E in --------studied the feasibilty of noninvasive monitoring of patients with acute medical emergency conditions in emergency department to prospectively evaluate the circulatory patterns in 151 consequtively monitored patients in emergency department. Pulse oximetry was one of the important parameters to effectively estimate pulmonary function .

Summers RL,Anders RM , Woodwords LH, Jenkins AK--in-------- studied oxygen saturation of 1235 adults presenting to emergency department at University Hospital , 2.8% cases benefited from routine pulse oximetry while 40% of these patients required extended care . Although the number is small , missing of hypoxia would have been detrimental for life .

In -----------Stratmann B. ,Richter J.,Muhr G. studied the pulseoximetry measurements in preclinical cardiopulmonary resuscitation in 23 cases . In 83 % of these cases confidential reading were obtained which helped in quality control during cardiopulmonary resuscitatiion .

Shoemaker WC.,Wo CC, Bishop MH conducted a prospective study in --------comparing noninvasive monitoring Vs invasive monitoring in 60 critically ill patients presenting to emergency department. Ninety percent of these patients had clinically specific abnormalities. Transcutaneus oxygen saturation decreased in 39 % cases and oxygen saturation by pulseoximetry fell in 22 % cases during observation period for first 2 to 8 hrs .Noninvasive monitoring was proved equally reliable as invasive monitoring .

In--- ---Brown LH, Manning EA, Komegay HB undertook astudy of 180 patients by obtaining oxygen saturation by pulseoximetry on arrival to EMS for all patients. Ninety percent of these patients had unrecognised hypoxemia, and 85.2 % cases with unrecognised hypoxemia didnot complain of respiratory distress .They concluded that there are patients whose hypoxemia is unrecognised by EMS providers and this occurs frequently in patients who donot complain of respiratory distress.

Mower WR, Sache S, Niche EL in -----------studied the utility of routiine pulseoximetry in triage for screening patients in emergency department in 14059 cases. Of these 1175 cases had SPO2 less than 95% and in 6.6% cases diagnosis was changed while in 13.5% cases repeat SPO2 was asked for , resulting in significant changes in medical therapeutics in 11.4 % cases

Ander AB, Zwerdung RG, Dewitt TG in ----------- studied the clinical utility of pulseoximetry in pediatric emergency department, in 437 cases. Spo2 readings were reproducible with intraclass correlation of 0.87%.. Spo2 measurements changed the assessed degree of illness in 5.3 % cases, 13% cases were felt to be more ill and 37% cases to be less ill.Of these 11% cases were discharged. They concluded that SPO2 is a stable and practically reproducible mode impacting patient assessment and management.

Lambert MA, Crimlon J in -----------studied 50 patients in emerggency unit using pulseoximeter and compared the same with simultaneus arterial blood gas saturation obtained in 15 cases. Spo2 correlated with calculated values of arterial blood oxygen saturation .Pulse oximetry helped in identifying 42% cases with clinically unsuspected hypoxia.

In -----Silverston P performed roadside pulseoximetry in 25 cases with abnormal trauma score and found to be of benefit in detecting and monitoring hypoxia in patients with airway obstruction, depressed respiration due to head injury or chest trauma. He also commented portable oximetry as a valuable aid in prehospital monitoring and assessment of patients by EMS providers

q PULSE OXIMETRY IN PEDIATRIC MEDICINE :

Pulse oximetry and newborns:

oximetry and prematurity: In premature infants, administration of supplemental oxygen is associated with retinopathy of prematurity. The duration concentration and patterns of O₂ toxicity, all being implicated, empirical recommendations for arterial oxygen saturation in infants at risk for Retinopathy of prematurity to 90 to 95% range. Pulse oximeter, obviously can be applied to maintain the same²⁵

Oximetry has also been used to demonstrate that periodic breathing in premies and newborns being unrelated to occurrence of apneic spells²⁶. Oximetry may reduce the need for intensive care in low risk groups.

Correlation of pulse oximetry saturation with arterial oxygen saturation in neonates:in ------------- Brockway J. from Denver, studied 22 neonates with gestational ages 24 to 40 wks to determine accuracy of SPO₂ with PaO₂ (arterial), to concluded that PaO2 varied broadly with SPO2 in clinically acceptable range of SPO₂ 90-98% and the variability increased at higher SPO₂ values²⁷.

Possibly the greatest concern in the use of pulse oximetry in pediatric practice is the use of the technique in sick neonates.

Neonates and hyperoxia: Pulse oximetry is a safe alternative to protect the neonate from hyperoxia and subsequent retinal damage which is dangerous. Reliablity of pulse oximetry in detecting small changes in SPO₂>96% are associated with relatively large changed in PaO2³⁰Authors have stated that SPO₂ should be kept low <95%, the goal should be 90%. Also in newborns,oxygen dissociation curve of fetal Hb shifted to left, further increasing the error between PaO₂ & SPO₂, however it gets reduced as fetal Hb decreases with age²⁸.

Obrien LM, Stebbens VA, Poets CF in ----------- studied 90 infants throughout first 24 hours of life. Pulse oximetry saturation remained stable for first 24 hours of life, when it became significantly lower with p value <0.03. Range of Spo2 in first 24 hours was similar to that found in first month of life .In 23 cases episodes of prolonged desaturations upto 90% were noted.

Reddy VK, Holzmer IR, Wedgewood JF in ---------studied 101 fullterm newborns between 20 minutesb and 6 hours of age. Babies spent most of the time with SPO2 more than 96 % in all postnatal hours.Its was concluded that a newborn more than 20 minutes old with SpO2 less than 90% over several minutes should be further evaluated.

Pulse oximetry has been used to provided closed loop control of inspired O₂ concentration to neonates using target saturation between 94% & 96%³¹.

q Pulse oximetry and hypoxemia:

High prevalance of clinically unsuspected hypoxemia is perhaps the most famous disclosure that pulse oximetry has made. Pulse oximetry now accompanies and occupies most critical care arenas and outpatient emergency units and virtually every operating room in US. They are manufactured by more than 35 firms with 1989 annual world wide sales estimated at 65000 units at 200 $ million.

Incidence of hypoxia and hypoxemia was studied by Mollar et al in details in a single blind intraoperative study³². Severe hypoxemias with HbO₂ saturation measured by oximetry as <80% was recorded in 20% cases and 70% of these hypoxias were clinically undetectable.Binding the oximetry data increased number of patients experiencing major desaturation events³³.

In ------ Mckay & Noble found that 6% of a series of nearly 5000 anesthetics were involved in critical incidents of which 29 had 5po₂ <78%, separate examination of patients with holding oximetry and capnographic data from anesthetic team found that 59 major desaturations (SPO₂ <85%) events in 43 patient and 130 minor desaturations events (<95%) in rest were identified, of which 41 were first diagnosed by oximetry¹.

Hartert et al and Wheeler AP in ---------studied the use of pulse oximetry in recognizing the severity of airflow obstruction. 26 ICU patients with chronic lung disease or asthma were enrolled. They noticed pulsus paradoxus in 69% cases significantly correlating to SPO2 levels¹.

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Pulse oximetry and respiratory rate :

In --------- Mower WR ,Sache C, Nicklin EL, Safa P, Baraff LJ analysed the correlation of respiratory rate with oxygen saturation meaasured by pulseoximetry. Of the 12096 conseequtive EMS patients in this study; only 33% cases with Spo2 less than 90 % had increased respiratory rates. It concluded that respiratory rate measurements correlatedpoorly with SPO2 measurements and donot screen desaturations reliably. Patientswith low Spo2 donot usually exhibit increased respiratory rate.Increased respiratory rate is unlikely rto reflect desaturation.

Kelly AM, Mcalphine R, Kyle E in------------ conducted a study amongst 64 sample pairs of patients with chronic obstructive lung disease presenting to EMS with acute exacerbations .fourteen percent of these cases had significant hypoxia (PO2 < 60 %), with a correlation coefficient of 0.91.With respect to RO???C curve analysis ; the best cut off point oxygen saturation for detecting hypoxia was at SPO 90 % with 100 %sensitivity.

Oximetry and asthma:

Weigh and Santocci et al in ---------- evaluated the utility of pre and post treatment O2 saturation for prediction of admission or relapse in acute asthma exacerbations using a standardized treatment protocol and found that SPO2 as relatively poor predictor of admission and SPO2 <95% occurred only in 32% of patients, but can be used as an adjuvant to objectively confirm the need for admission³⁵

Sole D et al, Kamatsu MC, Carvallho KV in -------- evaluated 174 children with acute asthma and/or wheezing ; attending allergy clinic and emergency room and compared clinical symptoms and spirometric findings with SPO2 and documented significant correlation between decrease in clinical scores and in SPO2 following treatment with bronchodilators in both group of children; determining the prognostic value³⁶.Spo2 levels also correlated positivly with FEV1 & FEF and negatively correlated with clinical scores and heart rate. SPO2 less than 94% was associated with increased with increasing severity of asthma attatck.

Pavon D -in -------------- studied the relationship between pulse oximetry and clinical score in children with acute wheezing less than 24 months of age, they found that clinical score had a good correlation with SPO2 and concluded that if pulse oximetry is not available, it is advisable to include O2 in the treatment empirically³⁷.

Alano AJ, Lewander WJ ,Donnery P in -------- studied the relationship between oxygen saturation and clinical assessment in 74 infants and children presenting with acute wheezing. The results showed that before therapy, there were only weak correlations between SaO₂ and both respiratory rate and an index of respiratory distress in acutely wheezing infants and in children²⁸.While after therapy, children may appear clinically improved but may have variable SPO2 not correlating with clinical assessment.SPO2 was found to be inversly correlatingwith respiratory rate and an indexof respiratory distress, [prior to medications.

A study conducted by Cook and Stone et al in ----- concluded that for pediatric asthma patients with an initial SaO₂ <90%, increased SaO₂ after treatment initiated albuterol was predictive of clinical improvement. Patients with an initial SaO₂ <95% who do not have improved SaO₂ after treatment, require- further evaluation³⁹.

In ------- Yamamoto and Colleagues from Honolulu studied oxygen saturation and concentration changes during the treatment of wheezing in pediatric emergency department, concluded pulse oximetry as an objective means of assessing asthma severity⁴⁰.

Luaces Cubelle C, Garcia Garcia JJ, Garron Torrico P in ------evaluated the ability of Wood Downes Modified score and pulseoximetry oxygen saturation to identify children who need hospitalisation ; in 121 children .Although score values were better predictive of severity than Spo2 , SPO2 was proved as objective method of clinical assessment with cut off points for pre and post nebulisation at less than 92% and less than 96%; with sensitivity of 47 % comparable with 60% sensitivity of clinical score.

In ------- Guldager H, Spehn M divided 44 asthmatics in 2 groups with spo2 less than and more than 80%. Oximetry before treatment with a cut off point of Less than 80% had 18% specificity but 100 %sensitivity for predicting unfavourable outcome.

In ----------- Del Rio Navarro and Colleaggues published an artical on clinical usefulness of pulse oximetry in asthmatic children they found pulse oximetry as useful and simple method for an objective evaluation of acute asthma and its complications but it was not predictive for therapeutic decisions⁴².

Connett GJ and Lenney W of Royal Alexandra Hospital in ------- recorded SPO2 before and 10 minutes after salbutamol nebulisation in 75 children.A post nebulisation SPO2 of less than 91% had 100% sensitivity and had 86% positive predicitive value for need for intravenous therapy.

In ----- Bishop J, Nolan T evaluated the reliability of clinical asthma severity scale in 60 children from 6 to 17 years age; comparing with SPO2 readings classifying them as mild , moderate, severe .Asthma severity score more than three had 97% sensitivity for predicting admission. These findings were consistent with SPO2 score for predicting the severity of asthma.

Dawson KP in --------- carried out a clinical estimaate of asthma severity using a clinical score and oxygen saturation measurement by pulse oximetry on a group of 41 children more than 3 year age .At the time of admission to hospital with acute exacerbation, a correlation coefficient of -0.76 was observed.

Oximetry and BP Estimation :

Use of pulse oximetry for BP measurement is well known, though under investigaiton. Movlus et al has studied the pulse oximeter waveform changes with oscillometric studies and intraarterial measurement in children after cardiac surgery. He commented that pulse oximeter waveform change is an accurate and reliable way to measure blood pressure in children and is

superior to oscillometric method for small patients. It was found to be closely correlating with NIBP⁴³.

Pulse Oximetry and home oxygen therapy:

Oximetry has been used to demonstrate with periodic arterial blood gas determination, to help adjust flow rates and periods of use of home O₂ therapy of patients with chronic obstructive pulmonary disease e.g. in response to increased needs with exercise and rapid eye most sleep, a review by Tiep et al suggested that involvement of physician and oxygen supplier to demand and reduce possible excessive oxygenation and respiratory depression⁴⁴.

AARC clinical practice guidelines on pulseoximetry may 14; 2000 suggested pulse oximetry as a tool for monitoring of oxygen saturation at home especially in patients with chronic diseases involving respiratory or cardiovascular system; provided the caregiver is trained in changing oxygen concentration depending on the desaturation observed⁴⁵.

Pulse oximetry and procedures:

Bell suggested that during GI scopy, hypoxic problems are common with 60% of deaths during endoscopy, attributed to cardiovascular complications⁴⁶.

British society of gastroenterology has approved guidelines for pulse oximetry use as a standard during all procedures and also suggested that oxygen be administered⁴⁷.

Sedation and anesthesia are commonly used in oral surgery and dentistry without professional anesthesia. In view of potentially high incidence of hypoxia, pulse oximetry has been strongly recommended although Wilson suggested that 90% of desaturations in hours of study of 22 sedated children were due to motion artifact^48,49.

Airway management problems aided by oximetry include evaluations of performance of experimental devices like:

1) Glospalatine tube⁵⁰.

2) Detection of obstructed or misplaced endotracheal tube.

3) Respiratory tract obstruction by endotracheal tube.

4) Assessment of readiness for trachostomy⁶⁰.

5) Foreign body removal⁶¹

Mechanical ventilation and pulse oximetry:

Use of oximetry with ET CO2 instead of ABG: in assessing a patients ability to be separted from mechanical ventilation was studied in 60 patients by withington et al pulse oximetry has been used in optimising CPAP and PEEP and for quantitative purposes it has been a documented help in many procedures such as determination of needed O2 flow rate or cone in ventilator dependent patients⁶².

In a study in general hospital with non critical care unit, 75% of patients monitored for 36 hrs had at least one episode of desaturation to < 90% and 58% had <85% few of these were documented and even availability of monitoring little effect on care⁶³.

Experimental trials with pulse oximetry:

· Use of pulse oximetry of its plethysmographic capability has been proposed as a monitor of circulatory adequacy but the pulsable perfusion required to generate a pulse signal on a given oximeter is not a primary and neither necessary nor sufficient to guarantee adequacy of circulation for a given application⁶⁴.

Systolic BP may be accurately determined by reappearance of pulsable waveform during cuff deflation in instrument that display the waveform or perhaps more accurately by waveform disappearance during slow cuff inflation⁶⁵.

· Comparison of pulse amplitudes on finger and toe demonstrated toe vasodilatation due to sympathetic blockade with spinal anaesthesia⁷⁸ it is superior to oscillometric method in children⁶⁷.

PULSE OXIMETRY AND NURSING

Ø Pulse oximetry is a boost to nursing care speciality by assessing O2 demand and adjusting O2 supply to individual patients as per requirement also in early detection of desaturation for early intervention⁶⁸.

v Oximetry as 5^th vital sign

The reliability and simplicity of pulse oximetry have led some to promote its use as a fifth vital sign^4,8.

Over the years, it is concluded that using pulse oximetry as a routine fifth vital sign results in important changes in treatment of small proportion of pediatric patients⁴.Mower et al and coworkers in ----------- conducted a prospective study to examine the use of routine oximetry screening of children presenting to emergency department or triage center. They measured SaO₂ of all children presenting to emergency triage and findings were revealed to physicians only after they had completed their evaluation of each child and then measured the changes in medical treatment. According to this study, only 4.8% of children with SaO₂ <90% had respiratory rate evaluation above the 80^th percentile for their age and less than one third had rates in upper 5^th percentile for their age.

It was also concluded that patients with pulmonary disease such as viral respiratory tract, infectious, pneumonia asthma and bronchitis was most likely to have abnormal pulse oximetry values and were also most likely to have their medical treatment changed⁴.Also they found poor correlation of respiratory rate with SPO₂. Although use of antibiotics and other treatment, after the patient outcome significantly, the true utility of pulse oximetry will be in how accurately these surrogate measures reflect improvement in patient outcome.

· A similar study was performed in geriatric patients, to study efficacy of pulse oximetry as fifth vital parameter. They studied 1963 adults more than 65 years age presenting to triage department and findings of SPO2 were compared with xray, arterial blood gas, spirometry and clinical change in treatment schedule.397 patients of 1963 had desaturation below 95 % which was clinically missed. After disclosing pulse oximetry results repeat reading was asked for in 51% cases. For 44 patients new treatment was adviced and oxygen was added to 29 patients⁶⁹.

Pulse oximetry and arterial blood gas saturation

· Use of arterial blood gas analysis has decreased in critical care arenas because of pulse oximetry, but ABG remains essential for pH and PCO₂ measurements for high PO₂ analysis in the determination of shunts, for instances when pulse oximetry fails and for confirmation of low SPO₂⁷⁰.

· In 30 patients during emergency field rescue operations, SPO2 was compared with arterial blood HbO2 and found to correlate with

r = 0.898 and bias of SPO2 to O2Hb of – 0.3 to ± 2.4⁴⁹.

· By 1988, institutional surveys had already suggested that pulse oximetry had reduced the need for ABG analysis on various hospital services. This was supplemented in 1991 by a study of 20,120 emergency room visits in which physician orders for ABG analysis, decreased by 37; without adversely affecting the quality of emergency case^71,72.

· Lee et al and Mayberry K studied 664 consecutive patients presenting to emergency unit and compared SPO2 readings with ABG readings. They found that COHb was the only statistically significant factor affecting the accurance of pulse oximetry. COHb <2% caused SPO2 over estimation by 4 % in only 2.4 % cases while COHb more than 4 % in 35 % cases . /They stated SPO2 92 % as having best pulmonary threshold for hypoxia⁷³

· According to a study published in 1991, 20120 patients were included in whom requirement for ABG was tested. They found that before oximetry was unavailable 699 ABG s were performed but after oximeter was available only 440 ABG s were ordered thus it may decrease rate of ABG testing⁷⁴.

· Continuous emergency department monitoring of SPO2 was studied by Jones J , Heischmann D, Cannon L, Gradisel R in a prospective uncontrolled study of 40 patients presenting to emergency department..Additionally , the early earning capability of SPO2 monitoring was also analysed. These readings correlated with arterial blood oxygen saturation and it detected several otherwise unrecignised drops in arterial oxygen saturation, confirmed by ABG ; helping to improve the precision of the therapy.

Bourdelles G, Estagnasie P, LenoisF, Brun P, Dreyfuss D studied SPO2 and its impact on indication and number of arterial blood gas analysis; in 152 patients. ABG was measured in 119 patients. Eighty eight percent cases were justified for ABG .Availability of pulseoximetry didnot affect the ordering of useful ABGs but allowed significant reduction of unjustified ABGs.

Pulse oximetry and poor peripheral perfusion and hypothermia:

A study on 19 children, 10 years old, to examine the effects of perfusion on accuracy of pulse oximetry was done to determine threshold for perfusion below which the oximeters become inaccurate and cease to function simultaneous hemoxymetry was continued and bias SpO₂ and SaO₂ of each oximeter is compared to each perfusion variable age, weight, temperature, Hb pulse pressure, 4% flow by doppler to determine effect on assurance⁷⁵.

It was found that all there parameters had a little effect on accuracy of pulse oximetry in children, and only skin temperature below 30° C is identified a significant predictor of inaccuracy.

Pulse oximetery and anemia :

Retrospective analysis in tests of 43 oximeters of 12 manufactures disclosed a negative error, inversely proportional to Hb concentration when SaO₂ was < 80%. The mean error when SaO₂ 54.5% appeared to be a clearly linear function of Hb concentration With no error < 14.5g/ m of which 8% could be attributed to anemia. This was ‘fail safe’ error, providing exaggerated warning of hypoxemia in anemia. In 27 burned patients despite anemia and edema, no errors / problems were detected in the use of pulse oximeters^76,77.

Oximetry and patients safety :

Pulse oximetry is judged by many anesthetists and demonstrated as superior to clinical judgement and capnography in providing early warning of hypoxic events.

Although this capability is accepted prima facie as impressive and valuable by most anesthesiologists, it is equally impressive that no published investigation has yet demonstrated that pulse oximetry makes a differences in morbidity and mortality.

Task of making such determination is daunting in v/o relatively large no of patients required.

In general, the myriad studies documenting clinically indetectable hypoxemia aim only at description. They do not answer questions like what kind of desaturation is unacceptable under what circumstances? for how long? in whom? no answer will ever satisfy all conditions for all observers and patients⁷⁸.

At the physiological level, recent pulse oximetry data do provide some surprises about how tolerable severe hypoxemia is in humans

Saturation cycling repeatedly down to 30 to 40 % has been recorded during sleep without detectable brain or other systemic damage, both in subject with chronic mountain polycythemia and obesity associated chronic obstructive lung disease and obstructive sleep apnoea. In addition, the subtle evidence of permanent brain injury reported by Horenbain et al. Mount Everest climbers was found in those who had best hypoxic ventilatory drive and who therefore were presumed to have been hypoxic/ but most hypocapnic during exposure⁷⁹.

On other hand, when we find SpO₂ decreasing from normal to 90% without evident cause, we may well judge, this sufficiently unacceptable to warrant further investigation and treatment.

The near uncritical enthusiasm that greeted the introduction of pulse oximetery has become tempered, especially in past 5 years by commentary regarding the paucity of risk / benefit data. Prima facie clinical impressions need not bear any relationship to what might be demonstrable via that grail of clinical research⁸⁰

Cooper et al in 1987, recorded few impact events like hypotension a dysrhythmia in few pediatric post operative patient but a cause effect relationship was not elicitable.

Need for comparable routine use during transport and recovery is supported by evidence of hypoxic injury after discontinuation of operating room [Closed Claims Project]. If pulse oximetry would have been available. In view of these recent developments clinical investigations about the benefits of pulse oximetry continue to ** progress with rigorous coroboration.

AIMS AND OBJECTIVES

1) This study was performed to demonstrate the accuracy of pulse oximetry in determining oxygen saturation by comparing with oxygen saturation of arterial blood, and also to study its correlation with partial pressure of O2 if any.

2) To correlate pulse oximetry saturation with other vital parameters of routine assessment also judging the severity of disease by clinical score.

3) To determine if any relation between on admission pulse oximetry saturation and duration of hospital stay or the IPCU stay or death, if any.

4) Also overall, we assessed whether non invasive pulse oximetry saturation can be considered either equivalent or superior vital parameter as compared to traditional parameters.

METHODOLOGY AND STUDY DESIGN

This prospective study was conducted at emergency pediatric care unit of a tertiary care hospital, where all the sick children presenting to the hospital are referred for assessment & further management.

This prospective study was conducted over a period of 10 months where by successive pediatric admissions to emergency pediatric unit were included in the study .The surgical cases, cases transferred directly from other hospital and the cases whose pulse oximetry or ABG reading could not be taken were excluded

INCLUSION CRITERIA

a) All children referred to or presenting to emergency pediatric care units, during the period of study, requiring admission and / or monitoring of the child for atleast 6 hrs necessitating a hospital admission

b) Age 1 month to 12 years of either sex.

EXCLUSION CRITERIA

All minor conditions who did not require clinical monitoring or investigations depending on the clinical judgement of attendant pediatrician and the investigator.

Surgical cases were excluded by our triage department from the study.

The children presenting to emergency department/ward were examined by emergency pediatrician on duty and the investigator simultaneously.

As soon as any sick child was referred, a short history and adequate emergency examination of vital parameters was noted and also emergency investigations were done as per the requirement, along with pulse oximetry saturation measurement.

A decision was taken based on clinical presentation and available investigations regarding the management of the case.

Accordingly the patient was either admitted or sent home with medications to follow up on OPD basis; detailed clinical history and examination was carried out by the investigator and recorded on the proforma.

The attendant pediatrician however continued the management including investigations & treatment not interrupted by the investigator.

Temperature was recorded with the help of simple thermometer. Routinely axillary temperature was recorded and noted down in proforma by the investigator. All abnormal readings of temperature are confirmed by rectal temperature and repeated after 30min.

Pulse was measured by the investigator over full one minute and its rate and rhythm noted in the proforma.

Respiratory rate over one minute with respiratory distress of any severity was documented on the proforma.

Blood pressure of all children was documented by noninvasive blood pressure instrument using the appropriate size cuff for age, in right arm supine position and confirmed by manual blood pressure instrument.

Pulse oximetry saturation was recorded by the investigator using same standard & oximeter. Consistant readings are noted down on the proforma recorded in within 5min.

A General examination was extended to look for markers of sepsis, shock, dehydration, anemia and edema, while the attendant pediatrician continued the management.

A detailed systemic examination was carried out and abnormal findings if any in each system were noted and given a clinical judgement score of 0,1,2 depending on no finding, some finding and significant finding respectively.

All the data and examination finding were available to attendant pediatrician & disclosed to him on demand.

We estimated arterial blood gas analysis of all patients. The oxygen saturation and PO₂ were noted down on proforma.

Childs clinical course in the hospital was followed with regards the requirement of stay in emergency medical department ICU or pediatric ICU, the no of days in ICU if any and also death in the course of illness if any was documented alongwith the duration of hospital stay.

Of all 110 children included in the study, the proforma was completed by the investigator. Each case was given a serial number in sequence and the results were analysed.by simple statistical methods and correlations were determined by 't' test.

OBSERVATION AND RESULTS

ANALYSIS

TABLE 1 : Age distribution of cases

Of the total 110 patients admitted during the period of the study 31 (28.18%) patients were infants , 51 patients (46.36%) were from age group 1-5 ye ars and 28 patients (25.46) were from age 5 to 12 years.

Age groups	Males		Females		Total
Age groups	No.	%	No.	%	Total
£1yr	18	25.7	13	32.5	31 (28.1%) of total
1 to £5yr	39	55.4	12	30	51 (46.3%) of total
>5yr	13	18.6	15	37.0	28 (25.6%) of total
Total	70		40		110

TABLE 2 : Sex distribution of cases

Among these admissions to emergency pediatric department 70 cases (63.6%) cases were males while 40 cases (36.6%) cases were females.

TABLE 2 : Sex distribution

Sex	No	%
Male	70	63.64
Female	40	36.36
Total	110	100

TABLE 3 : Systemic distribution of cases

. System	Admissions
. System	No	%
RS	39	35.3
CVS	14	12.6
CNS	20	18.1
CVS + RS	4	3.5
CNS + CVS	3	2.6
GI + Hepatorenal	10	9.0
Mixed	12	11.7
Miscellaneous	8	7.1
Total	110	100.0

39 patients out of 110 admissions were solely from respiratory system, contributing to 35.45 % cases admitted in emergency pediatric department Neurological cases amounted the second largest group were 20 (18.18%) out of 110 , 14 cases (12.7%) had solely CVS involvement while 7cases (6.3%) had complex involvement of cardiovascular system with respiratory and neurological illnesses.

10.9 % cases had mixed system affection of various systems while 7.27% cases were admitted for miscellaneus illnesses. Only 9 % of admitted cases had gastrointestinal or hepatorenal illnesses.

TABLE 4 : Correlation of pulse oximetry saturation and arterial blood gas saturation of oxygen

®Sao2	Upto 40		41 –50		51-60		61-70		71-80		81-90		90-91		Total
SPO₂¯	Upto 40		41 –50		51-60		61-70		71-80		81-90		90-91		Total
	No	%	No	%	No	%	No	%	No	%	No	%	No	%	No	%
Upto 40	1+1		1		1											2.75
41– 50											1				1	0.92
51 – 60	1														1	0.92
61 – 70	1				3		2						1		7	6.42
71 – 80	2		2		2				1				1		8	7.34
81 – 90					2		10		3		2		1		18	16.5
91- 100					3		9		36		15		6		71	65.14
Total	6	*4.59*	5	*4.59*	11	*10.09*	21	*19.27*	41	*37.60*	17	*15.60*	9	8**	*110*	*100*

Correlation coefficient = +0.62

Significance of ‘e’ by ‘t’ 8.14 **

The pulse oximetry saturation was measured and compared with arterial blood gas saturation in all cases.A graph of same was plotted. Statistically a correlation cpoefficient of 0.88was deduced ; it’s significance by ‘t’ test was 19.17 suggesting p value 0.001 as high correlation.

TABLE 5 : Correlation of pulse oximetry with arterial oxygen pressure

PO2Þ	60 – 70		71 – 80		81-90%		91-100%		Total
SPO2 % ß	No.	%	No.	%	No.	%	No.	%	No.	%
Upto 40	1	-	-	-	-	-	-	-	1	0.92
41 – 50	1	-	-	-	-	-	-	-	1	0.92
50 – 60	1	-	-	-	-	-	-	-	1	0.92
61 – 70	4	-	-	-	1	-	-	-	5	4.59
71 – 80	1	-	7	-	-	-	-	-	8	7.34
81 – 90	-	-	-	-	16	-	2	-	18	16.51
91 – 100	-	-	2	-	-	-	73	-	75	68.80
Total	8	7.33	9	8.26	17	15.60	75	68.81	109	100

Correlation coeff : r’r +0.884

Significance of ‘r’ by : ‘t’ : 19.97 P < 0.004

As arterial blood saturation is a function of partial pressure of oxygen in arterial blood ; a graph of SpO₂with PO₂ was plotted. A correlation coefficient ‘r’ of +0.62 was deduced. It’s significance by ‘t’ test was 8.14 with a p value of <0.001.

TABLE 6: Pulse oximetry saturation distribution among EPD admissions

For sake of simplicity and for detection of early desaturations; a desaturation scale was deviced based on SPO_2.As, many times, pulse oximetry desaturations were noticed in early phases of disease / hypoxia, when clinical signs/symptoms are not manifest, we analysed our patients with above modified scoring system. SPO₂ readings were classified, & analysed with respect to age & sex distribution and disease distribution and were correlated with T,P,R,BP, Hb, SaO₂, PO₂ to detect presence of correlation if any.

SATURATION SCORING SCALE

SPO₂ score	SPO₂ level	Desaturation Grade
0	>96 %	Normal SPO2; no desaturation
1	92% to 96% including 96%	Mild desaturation; mild hypoxia
2	87% to92 % including 92%	Moderate desaturation Or mod. Hypoxia
3	Less than 87% or 87%	Severe hypoxia or severe desaturation

By this scale , out of 110 patients under study ,only 28 cases (25.45 %) had perfectly normal saturation..Rest of the 74.4% cases had variable grades of desaturations.

While only 37 (15.45%) cases had moderate desaturations; 28 (25.4%) cases had severe desaturations.

TABLE 7 : Saturation distribution of diseases

System	SPO2 %
	> 96		92 to £96		87 to £92		< 87		Total
	Nos.	%	Nos.	%	Nos.	%	Nos	%	Nos	%
RS	2	1.82	16	14.55	10	9.09	11	10.0	39	35.45
C.V.S.	2	1.82	6	5.45	2	1.82	4	3.64	14	12.73
C.N.S.	11	10.00	7	6.36	1	0.90	1	0.90	20	18.18
Mixed	1	0.90	2	1.82	2	1.82	7	6.36	12	10.90
Misc.	5	4.55	2	1.82	1	0.90	-	-	8	7.27
RS + CVS	-	-	1	0.90	1	0.90	2	1.82	4	3.64
C.N.S.+CVS	-	-	-	-	-	-	3	2.73	3	2.73
GI + HR	7	6.36	3	2.73	-	-	-	-	10	9.09
Total	28	25.45	37	33.64	17	15.45	28	25.45	110	100

Respiratory diseases : Of total 39 patients with respiratory system affection, 16 (41%) cases had only mild desaturations, 10 (25% )cases had moderate desaturations and 11 (28.6 %) cases had severe desaturations. Only 2 (5%) of cases admitted with respiratory system affection had normal SPO_2..

· Cardiovascular illnesses : Of 14 admissions for cardiovascular illnesses, 6 (42.8% ) cases had mild desaturations, 2 (14.3%) cases had moderate desaturations and only 2 (14.3%) cases had normal SPO₂. There were 3 cases of congenital heart diseases.

In seven cases apart from those 14 cases mentioned above, there was secondary respiratory and neurological complication. All of these 7 cases had desaturations and 5 of these had desaturations less than 87 %.

· Neurological illnesses :Out of 20 cases admitted with neurological illnesses 11 children (55%) had perfectly normal SPO₂.Nine cases (45%) had desaturations of which only one case had severe desaturation.

· Mixed systems illnesses :12 cases (10%) under study had affection of different systems in different proportions. Of them only one case had normal saturation and 7 cases had severe desaturations on admission.

· Table 8: Age distribution of SPO₂

Age	SPO2
Spo2 score	> 96 0		92 to £96 1		87 to £92 2		< 87 3		Total
	Nos.	%	Nos.	%	Nos.	%	Nos	%	Nos	%
£ 1 yr	4	3.64	10	9.09	8	7.26.	9	8.18	31	28.18
1–5 yr	11	10.0	19	17.27	7	31.8	14	12.73	51	46.18
> 5 yr	13	11.82	8	7.27	2	15.4	5	4.55	28	25.46
Total	28	25.45	37	33.64	17	5267	28	25.45	110	100

Amongst infants (31 cases), 10 cases had only mild desaturations while 8 cases had moderate desaturations and 9 cases had severe desaturations. Only 4 of infants admitted to emergency pediatric unit had normal SPO_2.

Of the 110 patients admitted to emergency pediatric unit, 51 (46.1%) cases were from 1 to 5 year age group, amongst these 7 (31.8%) cases had moderate desaturations and 14 (12.73%) cases had severe desaturations, while only 11(10%) cases had normal SPO₂.

Amongst children more than five year old (28 cases), 15 cases had desaturation and 13 (11.8%) cases had normal SPO₂. Of these 8 (7.27%) cases had only mild desaturations and 5 (4.55%) cases had severe desaturations.

Sex	SPO2 %
	> 96		92 to £96		87 to £92		< 87		Total
	Nos	%	Nos.	%	Nos.	%	Nos	%	Nos	%
Male [%of total cases]	18	16.36	21	19.10	11	10.0	20	18.18	70	63.64
Female[%of total cases]	10	9.09	16	14.54	6	5.45	8	7.27	40	36.36
Total [%of total cases]	28	25.45	37	33.64	17	15.45	28	25.45	110	100

TABLE 9 : Saturation distribution of patients transfer to PICU

	SPO2
	> 96		92 to £96		87 to £92		< 87		Total
	Nos	%	Nos.	%	Nos.	%	Nos	%	Nos	%
IPCU Admission
IPCU Admission	4	3.64	10	9.09	9	8.18	22	20	45	40.90
% of IPCU cases	10	8.89	16	22.22	6	20	8	48.88	40	100

As mentioned already, patients were stabilized in the emergency pediatric department and then transferred to general ward or PICU for further management of the illness.

Amongst patients admitted in emergency pediatric department during the period of study, 65 (59%) of cases did not require intensive care, of which 24 (34%) cases had normal SPO₂. 27 (40%) of these cases had only mild desaturations and only 6 (26%) cases who had significant desaturations did not require PICU transfer.

Of those 45 cases (40.9%) transferred to PICU for various reasons, only 4 (8.9%) cases had normal SPO₂ and 22 cases (48.8%) had severe desaturations on admission. While 10 (22%) cases had mild desaturationson SPO2, 9 patients (21%) had severe desaturations on SPO ₂ before transfer to PICU.

TABLE 10 : SPO₂ di stribution In PICU deaths

	SPO2
	> 96 normal			92 to £96 mild desaturation		87 to £92 moderate desaturation			< 87 severe desaturation			Total Cases
Deaths		No	%	No	%		No	%		No	%	No	%
		1	0.90	3	2.73		3	2.73		10	9.09	17	15.45
Out of 45 IPCU admission			2.22		6.67			6.67			22.22		15.45

Amongst all 110 admissions, 17 cases (15.45%) expired of various reasons after variable period of PICU stay.

Out of 17 deaths only one case had normal SPO₂ and 10 cases out of 17 deaths had severe desaturation on SPO₂scale on admission. Three cases had mild desaturation and three cases had moderate desaturation on SPO_2.

TABLE 11 : Variation of SPO₂with temperature

SPO2 / Temperature		Normal 0	Mild desaturation 1	Moderate desaturation 2	Severe desaturation3	Total
Abnormal	Low	1	4	1	3	9	37 33.6%
Abnormal	High	11	6	6	5	28	37 33.6%
Normal temperature		16	27	10	20	73 (66.3%)
Total		28	37	17	28	110 (100%)

37 cases had abnormal temperature amounting to 33% of all 110 admissions. Of these only 9 were hypothermic. Amongst these only one had normal SPO₂ despite hypothermia. Overall 12 (34%) cases with abnormal temperature had normal saturation. Amongst those 73 cases who had normal temperature on admission; 57 cases (79.8%) had significant desaturations.

We could not deduce any statistical correlation between abnormal low or high temperature and SPO₂.

TABLE 12 : Correlation of SPO₂ with pulse rate

Spo₂Pulse	Normal 0	Mild 1	Moderate 2	Severe 3	Total
< 80	0	0	0	2	2
80 to 140	21 (31.8%)	22 (33.33%)	9 (13.6%)	14 (21.2%)	66 (100%)
140 & above	7 (16.6%)	15 (35.7%)	8 (19.0%)	12 (28.5%)	42 (100%)
Total	28	37	17	28	110

Age independent assessment of pulse rate with SPO₂ was plotted .Out of the 44 cases with abnormal pulse rate , only 7 cases (16%) had normal SPO₂. A graph of SPO2 with pulse rate was plotted ; although no statistical correlation was found . In any level of SPO₂ incidence of normal or abnormal pulse rate children does not differ except in SPO₂ level (81.10%).

TABLE 13 : Pulse oxymetry saturation and blood pressure changes

Blood pressure		No. of cases with Spo₂as below								Total
		Normal 0		Mild 1		Moderate 2		Severe 3
Normal BP		24 (24.4%)		36 (36.7%)		15 (15.3%)		23 (23.4%)		98 (100%)
Abnormal	Low	2	4 (33%)	0	1	2	2	5	5 (41%)	9	12 (100%)
	High	2		1		0		0		3
Total		28		37		17		28		110

Only 12 cases out of 110 patients admitted during the course of study had abnormally low or high blood pressure. Among those who had abnormal blood pressure 8 (66%) cases had severe desaturations of 98 cases who had normal blood pressure on admission 74 (75.5%) cases had significant desaturations as seen from the above table. Of these 23 (23.4%) cases had severe desaturations.

TABLE 14 : Pulse oximetry saturations and respiratory rate

Respiratory rate		No. of cases with Spo₂as below								Total
		Normal 0		Mild 1		Moderate 2		Severe 3
Normal RR		25 (13.8%)		33 (40.7%)		11 (13.5%)		12 (14.8%)		81 (100%)
Abnormal	Low	2	3	0	4	0	6 (21.4%)	4	16 (57.1%)	6	29 (100%)
	High	1		4		6		12		23
Total		28		37		17		28		110

Out of total 110 patients 81 patients (72%) had normal respiratory rate and of these only 25 (13.8%) cases had normal saturation. Out of 28 cases with normal SPO₂ only 3 cases had abnormal respiratory rate while amongst 26 cases with abnormal respiratory rate had significant desaturation.

TABLE 15 : Pulse oximetry saturation and blood haemoglobin level

SPO₂
Hb	Normal 0	Mild 1	Moderate 2	Severe 3	Total
<4 gm%	2	3	0	1	4
4-6 gm%	1	2	0	3	6
6-8gm%	2	8	0	12	22
8-10gm%	21	20	16	3	60
10-12gm%	1	3	1	5	10
> 12gm%	1	1	0	4	6

Of 10 cases with Hb < 6gm% 4 cases has severe desaturation and
3 cases had completely normal SPO₂ severe desaturations were observed in 4 cases with Hb 12gm% .

A graph of SPO₂ with Hb was ploted but no statistical correlation could be deduced.

TABLE 16 : pulse oximetry saturations and X-ray chest abnormality

SPO₂
X- ray chest	Normal	Mild	Moderate	Severe	Total
Normal (38.2%)	24 (35.29%)	26 (38.23%)	9 (13.23%)	9 (13.23%)	68 (100%)
Abnormal (61.8%)	4 (9.5%)	11 (26.1%)	8 (19.0%)	19 (45.2%)	42 (100%)

42 cases out of 110 admissions to emergency pediatric department had abnormal X-ray chest, of these only 4 cases had normal SPO₂ and rest of them had significant desaturations of the 68 cases who had normal X-ray chest only 24 cases (35.29%) had normal SPO₂.
TABLE 17 : correlation of Spo2 with duration of hospital stay

SPO2 %	Hospital stay
	< 3 days		3 to 10 days		10 days % Above
	No.	%	No.	%	No.	%
Upto 40	1	0.90	-	-	2	1.82
41 – 50	-	-	-	-	1	0.90
50 – 60	-	-	-	-	1	0.90
61 – 70	-	-	1	0.90	3	2.73
71 – 80	2	1.82	3	2.73	3	2.73
81 – 90	2	1.82	6	5.45	10	9.09
91 – 100	20	18.18	31	28.18	24	21.82
Total	25	22.72	41	37.27	44	**

All of the children who were discharged within 3 days of admission had SPO2 more than 70 % on pulse oximetry except one case of cyanotic congenital heart disease ;which had severe baseline desaturation , and 4 other cases of congenital heart disease had SPO2 between 70 to 90 %. Of those 44 cases having hospital stay more than 10 days, 24 cases had SPO2 above 90 % and 20 cases had severe desaturations.

DISCUSSION

Use of simple clinical signs in assessing cardiopulmonary status in infants & children is well recognised so are many emergency assessment scales deviced for assessing a sick child. In general studies show that cardiopulmonary disease is frequently present when these signs are manifest. But of equal importance are studies of many children who have significant cardiorespiratory illness but none of these clinical signs⁴.

Data from physiological studies indicate that mild to moderate hypoxia produces at most and modest increase in ventilation (ref). Transient hypoventilation is rapidly followed by a compensatory return to normal ventilatory rates. This biphasic response is a result of respiratory centre situated in brain stem.

Moderate hypoxia initially stimulates peripheral receptors to increase ventilation, however increased ventilation produces a decrease in arterial CO₂ pressure, an even more potent modulator of ventilation. In response to decreased partial pressure of carbon dioxide and because of direct control respiratory drive is down regulated to normal levels⁸²

Decrease in PO₂ to 50mmHg or less produces a sustained increase in ventilation; as the respiratory stimulation produced by hypoxia exceeds the inhibition generated by decreasing PCO₂ levels, an increased rate will usually be late response to hypoxia.

So is the response of heart and other body tissues to hypoxia. This manifesting as derangement of all traditional vital parameters of assessment, either in the form of delayed response to hypoxia or even if any response or sign manifests; may get compensated by body’s autoregulatory mechanisms unless the hypoxia is severe enough to produce sustained decompensation.

Aim of our study was to find out if we could bridge the gap between un diagnosed critical illness and vital parameters by using pulse oximetry. Also we studied whether it can be used as an additional vital parameter; being non invasive.

Pulse oximetry is infact nowadays replacing arterial blood gas analysis in early detection of hypoxia, by its accuracy, ease reliability and noninvasiveness^4,23. Pulse oximetry was proved superior to respiratory rate and other vita parameters in assessing severity of respiratory decompensation⁴.

In our study we tried to determine the usefulness of pulse oximetry in emergency pediatric medicine and compared it with other commonly used parameters of assessment of sick child in emergency department.

· Age variations :

As seen from Table 8, age group 1 to 5 years formed the maximum number of cases requiring emergency admission, 46.4% cases were solely from age group 1 to 5 years age and 28.2% cases were infants. This suggests that 74.6% of emergency admissions are under five year age, reflecting the vulnerability of growing children especially infants and toddlers for acquisition of illness. This in turn directs a thought towards increased under five mortality in children due to various diseases.

Also seen from the Table 8 that in admissions from all age groups, proportionately more infants suffered from hypoxia, compared to other age group. Of 31 infants under study, only 4 cases [14.2% of 31 cases] had normal SPO2, while 85.8% had desaturations less than 9.6%, 1/3^rd of which were severe hypoxia [sPo2<87%].

Similarly amongst 51 (46.18%) children from age group 1 to 5 years age, 76% of cases had significant desaturations (less compared to 85.8% of infants). Patients having severe desaturations (sPo₂<87%) formed 22.8% of these 51 cases.

The number of patients in the age group under 5 years of age and partricularly infants is higher and so is the total number of abnormal pulse oximetry readings in that age groups. This is not surprising as most of the children have cardiorespiratory problems and increased vulnarability of the airways of the younger children compared to elder children for infections is an important factor.

Overall, in all age groups, more than 2/3rd of emergency pediatric department admissions had on admission SPO₂ less 96% suggesting most of the patients requiring admissions have desaturations. Also 1/3^rd of these cases had severe desaturations (with SPO₂ <87%) irrespective of age and sex of child.

Thus, 66% of emergency pediatric department admissions had desaturations on pulse oximetry, which at times is not clinically suspected.

This may suggest role of pulse oximetry in emergency pediatric department, Emergency medical units and triage units for identifying seriously ill cases.

· Sex variations :

Of total 110 patients admitted during the study, 63.66% cases were males which is exactly 2/3 rd of total pediatric admissions during the study period, as seen from Table 1. This finding may be biased because of male dominant society, poor female literacy, poor health education, also only males may have been brought to emergency treatment with neglect towards girl child, or girls may have increased genetic potential to fight with infectious diseases.

Of total 110 cases 82 patients [74.6%] had some degree of desaturationon admission [sPo₂<96%]. Among these 36% cases were females and 64% cases were males. Thus nearly the same male to female ratio was observed in all subgroups of desaturations, suggesting spo₂readings as independent of sex of the child.

· Disease distribution :

For simplicity of analysis, for assessing degree of hypoxia and desaturations in different disease states, disease distribution of SPO₂ is plotted as in Table 3 and table 7. Of all pediatric patients presenting to emergency department; most cases will be cardiorespiratory diseases, accidents, injuries, minor infections etc.The same was evident from table 3 , however we had excluded all surgical cases from our study.

We also classified desaturations in different grades as shown in table below:

Spo2	grade	Desaturation
>96%	0	No desaturation i.e.normal
96 ³ and >92	I	Mild deasturations
92 ³and > 87	II	Moderate desaturations
³ 87	III	Severe desaturations

As seen from Table 3, respiratory illnesses contributed solely 35.45% of total admission in emergency pediatric department while cardiorespiratory illnesses together formed 54.55% of cases. Ten present of admission had mixed system affection while CNS admissions were 18.18%. As most of these admissions have cardiorespiratory system affection, hypoxia will definitely be more common in emergency pediatric department admissions, needing pulse oximety for early detection of the same.

Of total 39 (35.45%) respiratory cases admitted during study period, only 2[1.82%] of cases had normal SPO₂and 11 [10%)] of children had severe desaturation (less than 87%). 26 cases (23.6%) of cases had mild to moderate desaturation.

It is this group [grade I and grade III as shown above] of patients in which hypoxia may be most likely to be missed clinically.

Similarly among 14 patients with cardiovascular diseases, 2 cases had normal SPO₂ while. 12 cases abnormal desaturations [spo₂<96%] amongst which 1/3^rd cases had severe hypoxia [ SPO₂ <87%].

In contrast , total 20 (18.18%) of cases admitted with CNS illnesses 11 (10.0%) cases had completely normal saturation.

Amongst 12 cases (10.9%) with mixed system affection, only 1 case had completely normal SPO₂ being a case of disseminated tuberculosis.

All of 10 cases with gastrointestinal and hepatorenal illnesses had SPO₂ above 92%, even in cases of grade III dehydrations and in cases of acute renal failure. 1/3^rd of these cases had mild desaturation between 92 to 96% on pulse oximetry.

Thus maximum number of patients admitted to emergency pediatric department had cardiovascular or respiratory illness. And most of these cases (74.6%) had desaturation on pulse oximetry. Hypoxia was more severe and more common in patients with mixed system affection and in cases of sepsis. In contrast, despite significant CNS affection, even during seizures normal SPO₂ of >96% was observed in 2 cases: one case was of hypocalcemic seizures and other a case of TB meningitis.Asthmatics formed 60 % of respiratory admissions.SPO2 in these cases ranged from 85% to 96%.These findings were in consistent with the asthma severity score.This confirms with study by Luaces cubelleC and coworkers.

Amongst respiratory illnesses, lower respiratory tract infections and asthma exacerbations had characteristically mild to moderate desaturation. 16 cases of these 39 cases had only mild desaturation with SPO₂ 92 to 96%. In these cases clinically hypoxia was not suspected.

Among the children who had severe desaturation in respiratory illness were cases of empyema and foreignbody inhalation and cases of acute respiratory failure requiring ventilatory support.This finding again confirms the poor prognosis or protracted course in cases with SPO2 <80% , agreeing with study performed by Guldager and coworkers.

Cases of sepsis and other cases with mixed desaturations had SPO₂ <92%, suggesting significant hypoxia in these cases.

Although Emily El Al had studied the disease distribution of patients presenting to emergency pediatric department, and found incidence of respiratory illness to be 70%, no studies have documented SPO₂ variations in emergency pediatric department admission for different diseases / systems (Ref.). More studies are warranted to use pulse oximetry as a screening tool for different disease states, for judging the severity of hypoxia^4,82.

A study conducted by Mower et al.in ---------- in EPD using pulse oximetry on patients presenting to emergency pediatric department as screening tool and proved that in significant number of cases, the decision of admission, diagnosis, investigations and treatment was changed in different cases, after revealing SPO₂ to attending physicans (Ref.) There was 6% increase in diagnosis of respiratory illness and 12 % of patients had changes in treatment⁴.

This again proves importance of routine pulseoximetry screening in early detection of hypoxia.

· SPO₂ and arterial oxygen saturation sao₂:

As can be derived from Table 4, Table 5 and from graph of SPO₂ plotted against SaO₂, that pulse oximety is as effective as SPO₂ and can probably reduce the need for number og arterial blood gas requirements. It can also accurately predict arterial oxygen saturation as well as partial pressure of oxygen in arterial blood. This data supports the study by Lee et al who had also shown significant correlation of SPO₂ with SPO₂ in 350 children of different age groups (Ref). Another study performed by Shobitz et al in 400 pediatric intensive care patients, had found 63% decrease in incidence of ordering ABG anaslysis when SPO₂ was made available⁸³.Also this study confirms with the conclusion by Bardeller and coworkers that it causes significant reduction in unjustifiable ABGS.

As seen from the graph, there was a statistically significant correlation between SPO₂ and SaO₂ with P value <0.001. Finding confirming with above mentioned study by Lee et al⁸⁴.

Similarly, we found statistical correlation between SPO₂ & PO₂ with p value <0.001. Although PaO₂ varied broadly with SPO₂ in a clinically acceptable range 90 to 98%, the variability was high at higher SPO₂values.

This variation of SPO₂ and PO₂ at higher SPO₂ levels was following the shape of oxygen dissociation curve, when PO₂ crosses 85%, there is not much proportionate increase in the arterial oxygen saturation.

While graph of SPO₂ with SaO₂ was somewhat linear, showing proportionate rise, the graph of SPO₂ against PO₂ suggested clustering of cases at PO₂ of 70 to 80% and above 90%. Surprisingly. In both of these clusters, SPO₂ was above 90%, but <96% suggesting inability of SPO₂ to accurately predict PO₂when SPO₂ is above 85%. This study confirms the findings of Brockway et al. who studies 22 neonates to test accuracy of SPO₂ to detect PO₂²⁷ .

Diagram{}

The strong correlation of SPO2 and Sao2 has made pulse oximetry a vital tool in emergency medicine ; during transport of critically ill children to referal care centers and ambulatory critical care units, anesthesia care units and in neonatalogy. The noninvasive and continuous monitoring has practically eliminated the need for frequent ABG analysis. This could be more important in diseases involving multiple systems and cardiorespiratory illnesses.

· Intensive care transfers and correlation with saturation :

After emergency stabilisation, patients from emergency pediatric department were transferred to pediatric general ward or pediatric intensive care unit depending on the patients condition.

As seen from Table 9 and Table 10, 40.9% of emergency pediatric department admissions were transferred to PICU [pediatric intensive care unit] for further monitoring and management. Of these 45 cases who were transferred to PICU, only 4 (8.85%) cases had normal SPO₂[SPO₂ >96%], among these 4 cases was one case of tetanus which had completely normal saturation on SPO2 even during the spasms. Rest of them i.e. 41 cases (84.3%) cases had desaturations [SPO₂<96%]. Half of the PICU transfers had severe desaturation SPO₂ <87% and were transferred to PICU for mechanical ventilatory support, if required.

Of those 65 cases (i.e. 59.1%) who did not require IPCU transfer, 24 cases (34%) had normal SPO₂[>96%]. Majority [24.5%] of these cases (27 out of 65) had SPO₂ 93 to 96% suggesting only mild desaturation.

Of total 17 cases who expired during intensive care in PICU, only one case had normal SPO₂ on admission. The case was a 3 year old child with bacterial meningitis. Amongst rest of the cases, 59% of deaths had severe hypoxia with SPO₂ <87%, and 20% of deaths had mild and 20% had moderate desaturations on admission.

Thus from above findings it appears that early detection of hypoxia may help to anticipate progressive derangement. There is high incidence of hypoxia in patients admitted in intensive care unit, so is the incidence of death. So anticipation of hypoxia is of utmost importance by prompt detection and treatment towards eliminating the same. Those cases who had severe hypoxia, were in most instances fatal.

Studies on large scale are required to prove the same on statistical grounds.

Pulse oximetry may be an additional sign along with other vital parameters and screening systems like modified PRISM score and APACHE scores; which will not only aid in prognosis but also prove as an indicator of early transfer to PICU.

· Vital Parameters :

Traditionally, four vital parameters, temperature, pulse, respiratory and blood pressure, have been used to assess any child’s clinical status and seventy in emergency medicine. Mower et al has concluded that pulse oximetry is a superior vital sign and definitely more useful than respiratory rate in assessing hypoxia and clinical seventy out study confirms the same⁴.

a) SPO₂ and temperature :

As per Table 11, hypothermia was documented in only 9 cases amongst 110 cases under study. One third of these cases were associated with severe desaturations and hypoxia (with SPO₂ <87%), while one case with hypothermia had normal SPO_2.

Sixty six percent i.e. 7 cases out of 110, had completely normal body temperature on admission. Of these, 20.4% (16 cases) had normal SPO₂ and 79.6% case had varied grades of desaturation.

It was postulated that hypothermia is a signs of severe hypoxia, but what we can conclude now that it is a late sign of hypoxia as more than 79% of cases had desaturations despite normothermia. Desaturations postulated in case of hypothermia, were thought because of poor perfusion, inability of sensor to pickup signals in hypothermia, and association of hypothermia with clinical sepsis and general hypoxia⁸⁴.

But now with newer and modified available pulse oximeters, as used in this study, pulse oximetry was possible and equally rapid even in cases with profound hypothemia, thus proving it superior to temperature as vital parameter in judging and detecting early hypoxia.

We could not deduce any statistical correlation between SPO₂ and temperature.Hypothermia is one of the most important danger sign in newborns and small infants.Use of pulse oximetry is therefore well established in NICUs.

Ø Pulse oximetry and pulse rate :

As mentioned before in Table 12, 60% i.e. 66 cases out of 110 had normal pulse rate for the age, 2/3^rd of these cases had significant hypoxia on SPO₂ despite normal pulse rate.

While abnormally low pulse rate was associated with severe desaturations with SPO₂ < 87% same could not be extrapolated to abnormally high pulse rate. Although 38 % cases had abnormally high pulse rates, only 1/6 ^th cases had normal SPO₂

As its known that hypoxia can lead to cardiac decompensation to affect pulse rate, its not so in most of the cases. It may be because cardiac decompensation is a very late effect. Also, autoregulatory mechanisms correct slight derangements in cardiac activity, thus not manifesting clinically abnormal.

Thus even pulse rate is a relatively poor and late predictor of hypoxia, rather pulse oximetry is a superior parameter to detect hypoxia.

c) Pulse oximetry and Respiratory rate :

Although respiratory rate is a traditional vital parameter of assessment of respiratory system, hypoxia manifests first in the blood and lately as brainstem’s effect on peripheral respiration manifesting as tachypnea⁵. Highly variable estimation of respiratory rate in measuring the same, are known to vary from person⁴. Most of the time, the measurement of respiratory rate is erratic. In this study, only one and the same person assessed the respiratory rate in all cases, counting breaths for one complete minute thus avoiding the observer bias.

Even then 81 cases (73.6 %) had respiratory rates normal for the age. 67.2% of these cases had significant desaturations. Of those 26.4% cases with abnormal respiratory rate, 10.2% cases had completely normal SPO₂^.

Its clear that respiratory rate was normal in 73% cases despite significant hypoxia. And in those cases where it was abnormal, patient already had significant desaturations, except in 10% of cases in which spo2 was normal despite abnormalities of respiratory rate.

These results are consistent with study by Mower et al and coworkers. They found poor correlation between respiratory rate and pulse oximetry saturation. Mower et al had found the only 45% children with SPO₂ <90% had respiratory rate elevations for the age .

This study confirms the findings by Momen et al. in proving respiratory rate as relatively less significant parameter in detecting early hypoxia although it is superior most parameter in assessing hypoxia amongst traditional vital parameters. Clinicians may underestimate hypoxia in absence of respiratory distress, or may overestimate in cases where neurological alterations or metabolic alterations lead to tachypnea, despite normal SPO₂⁴.

Thus even respiratory rate, the most potent marker of respiratory system assessment, is not as prompt, accurate and reliable in assessing the degree of hypoxia, compared to pulse oximetry⁸. We plotted a graph of SPO₂against respiratory rate but could not deduce any statistical correlation.

d) Oximetry and BP :

Blood pressure of all these patients were compared with SPO₂. 98 of 110 cases had normal blood pressured within percentiles for the ages between two standard deviations. Only 10% of all admissions had abnormal blood pressure readings. This again suggests that changes in blood pressure are not evident untill severe desaturation. 2/3^rd of the patients with normal blood pressures had abnormal SPO₂. We also could not derive in statistical relationship between the same.

Using all there vital parameters together with their clinical findings, clinician / pediatrician on duty could suspect hypoxia clinically and ordered for an arterial blood gas analysis.

All the severe hypoxia cases, in who SPO₂ was <87% were detectable clinically by presence of respiratory distress, cyanosis or severe tachypnea

But only 5 out of 17 cases of with SPO₂ 87 to 92% i.e. moderate desaturations, were picked up clinically based on vital parameters and examination of child.

All the desaturations between 92 to 96% i.e. mild hypoxia were missed clinically, in fact 7 cases in who hypoxia was suspected in 6 cases (5.6%). It was missed in 44.4% of cases.

Thus we may conclude that vital parameters, either individual together with other clinical signs, tool for diagnosing early hypoxia in most of the cases, proving pulseoximetry superior to them for the same.

As there was not a single recordable case when all parameters were normal and pulse oximetry was abnormal, routine vital parameters are of utmost importance of emergency assessment in children and pulse oximetry may aid further assistance in patient care and management by early detection of hypoxia.

Pulse oximetry & capillary refill time:

Peripheral perfusion was poor in the form of delayed capillary refill time in 15.4% of the cases, and in all these cases SPO₂ was equally accurately & rapidly measurable with the help of modern pulse oximeters. All of them had significant desaturation confirmed by arterial blood gas analysis. The points that sensor may not pickup signals in poor peripheral perfusion, did not turn valid in our study, as we used a compatible modern pulse oximter. This study supports the findings of Daniel et al who while studying pulse oximetry efficacy in assessing poor peripheral perfusion, concluded that pulse oximeters are too good, specifically then contain extremely powerful amplifiers, that display SPO2 even when flow is critically compromised^1,75.

Capillary refill time may be an important sign to pick up in critically ill patients. All patients having prolonged capillary refill time had decreased SPO2 and it may be likely that these cases could be detected by decreased SPO2 alone before the capillary refill time falls.

Anemia and SPO₂ :

Anemia was common, seen in 45% of total cases under study. Although we could not device any statistical correlation between level of Hb & O₂ saturation, we may conclude that anemia by no means alters SPO2. SPO2 was normal even when Hb was 3 or 5 presenting as congestive cardiac failure. Out of 6 cases with Hb less than 5, only one case had severe desaturations while rest of them had mild desaturation. This finding were correlating with previous studies⁷⁶. Even at Hb 12gm% profound desaturation was observed in 2 cases because of the disease state. No studies are available to compare the same. Anaemia alone especially when mild could not cause significant desaturation. Saturation decreases only when anaemia is very severe and associated with other cardiopulmonary illness.

SPO2 and X-ray chest findings

Respiratory diseases are seen in a large number of patients presenting to emergency paediatric department. X-ray chest may give overall impression of lung involvement and hence x-ray chest findings were correlated with SPO₂.

38.2% i.e. 42 cases of 11o admissions had abnormal X-ray chest, of which only 4 cases had a normal SPO₂ and 43% had severe desaturations.

Of the 68 patients with normal x-ray chest, 35.4% of cases had normal SPO₂ and near 2/3^rd cases had shown desaturations. Further detailed studies are required in a larger population comparing the pattern of radiological presentations with degree of hypoxia to prove x-ray chest as important parameter to suggest hypoxia.

Abnormal X-ray findings were more likely to have low saturations again indicating that saturation is altered earliest in respiratory diseases.

Thus to summarise, progressive advances in pulse oximetry had made it stand in the course of time as a chief and one of the earliest parameter to detect even mild hypoxia. There are only few studies reported in the literature as discussed. We confirmed the same from the present study to prove pulse oximetry as the fifth vital signs in consistant with the study performed by Mower et al.

Conventional vital parameters along with other examinations are still important for assessing a critically ill child first presenting in the emergency room. Pulse oximetry being noninvasive , very easy and reliable,economical and accurate; can be used as an additional 'vital parameter' to manage sick children better.

LIMITATIONS OF THE STUDY AND GENERALISABILITY

1) The number of cases were small i.e. only 110 cases were studied in this project. So generalization of results may be questioned on statistical grounds.

2) Surgical, accidental cases and newborns were not included in this study.

3) Impact of pulse oximetry in altering the management of individual cases was not studied in details.

4) Usefulness of continuous pulseoximetry saturation monitoring was not studied.

5) Usefulness of pulse oximetry over arterial blood gas analysis needs a control group for comparision which was not considered.

6) The effect of pulseoximetry reading disclosure on investigations and patient care was not studied.Also the change in diagnosis, investigations and therapeutic modalities was not studied.

7) The outdoor patients and the patients which were not admitted in emergency hours were not studied which must have formed a significant chunk of pediatric hospital visits.

CONCLUSIONS

1) Pulse oximetry was independent of age and sex. Although infants and toddlers are more prone for hypoxemia.Also pulse oximetry was more useful for this age group.

2) Pulse oximetry saturation was an accurate and reliable method of estimating arterial blood gas saturation and arterial oxygen tension. It may reduce the number of ABGs ordered in a given situation.

3) Pulse oximetry could detect mild hypoxia accurately and results were comparable with arterial oxygen saturation.

4) Pulse oximetry was most useful in emergency pediatric medicine in assessing not only respiratory and cardiovascular illnesses but also in multisystem illnesses.

5) Respiratory and cardiovascular illnesses constituted two thirds of the pediatric hospital admissions and hypoxia was associated in twothirds of admitted cases with pulse oximetry saturation less than 96%.

6) Pulse oximetry saturation was independent of temperature. It was recordable even in severe hypothermia.

7) Pulse oximetry was superior to pulse rate in diagnosing mild to moderate physiological abnormalities and mild to moderate hypoxia.

8) Respiratory rate was poorely correlated with pulseoximetry saturation.In mild to moderate cases of hypoxia respiratory rates were normal for age .

9) Blood pressure changes were seen as a very late effect of hypoxemia.Pulse oximetry was superior to blood pressure in assessing hypoxia

10) Even in severe anemia, pulse oximetry saturation was accurately recordable.

11) Even in delayed peripheral perfusion, pulse oximetry was recordable. However judicial use of pulse oximetry bu continuous monitoring may help to pick up early signs as oxygen saturation was low in all cases with highly delayed peripheral perfusion.

12) Pulse oximetry in emergency department may prove as an indicator for early interventions or early intensive care.

13) Use of pulse oximetry as ‘fifth vital sign’ will prove cost effective and time saving resulting in better patient care and management.

OBSERVATION AND RESULTS

ANALYSIS

Age groups

Total

No

No