Oxygen is an essential element needed for life. Various parts of the
body have different oxygen needs. Nerve cells have a particular high need
for oxygen, and when deprived are particularly vulnerable.
1. Principles related to normal oxygenation (e.g., anatomy and
physiology)
Respiration
Respiration is the exchange of oxygen and carbon dioxide between an
organism and the atmosphere. The important thing to note is that
respiration it an exchange of two gasses, oxygen and carbon dioxide.
Carbon dioxide (CO2), a waste product of metabolism, is removed from the
body through the respiratory system. CO2 is an important component of
the acid base balance. Problems that interfere with oxygenation also often
interfere with the removal of CO2.
External and Internal Respiration
Two phases of respiration is the external respiration and the internal
respiration. External respiration is the transfer of oxygen and carbon
dioxide between inspired air to and from the pulmonary capillaries.
Internal respiration is the transfer of oxygen and carbon dioxide between
peripheral blood capillaries to and from the body cells.
Two systems are involved in oxygenation, the pulmonary system and
the cardiovascular system, often referred to as the combined
cardiopulmonary system. Problems in either system or insufficient oxygen
in the atmosphere are the sources for oxygenation problems.
Normal Respirations
For the adult in normal circumstances, the respiratory pattern is
regular, relaxed and quiet at the rate of 12 to 18 times per minute.
Inspiration is an active process of muscle contraction and expansion of the
thoractic volume, with expiration being a passive process with muscle
relaxation and compression of the thoractic volume.
The energy required for normal quiet breathing is only 3% of the
total body energy needs in normal healthy people. With difficulty, this
work of breathing is increased. In difficulty, people become very anxious,
and may be terrified. Prompt and emergent care is often needed to sustain
life. This immediate care also is important as anxiety can further induce
difficulties, aggravating the compromised situation.
Oxygenation
Oxygenation of the body involves five components;
atmospheric oxygen levels,
regulatory mechanisms for respiration,
ventilation or the movement of gasses from the external atmosphere
in and out of the lungs,
diffusion of oxygen and carbon dioxide from the alveoli and the
blood and from the blood and the tissue cells, and
perfusion or the movement of that blood throughout the body for the
transportation of the gasses.
Oxygen Levels and Partial Pressures
Normally oxygen is 20% of the atmospheric air at see level. The
pressure of all the gas in air at sea level is a total of 760 mm Hg. Oxygen at
21% of the total atmospheric gasses produces a partial pressure of 159.5
mm Hg.
Partial pressure is the pressure exerted by a single gas. Pressure is
measured in millimeters of mercury (also termed a torr where one torr
equals 1 mm Hg.)
A partial pressure is denoted by a "P" preceding the gas. This means
that the PO2 (partial pressure of oxygen) is 160 mm Hg or torr (159.5 mm
Hg rounded up).
Nitrogen, the most abundant atmospheric gas, composes 79% of air at
sea level producing a partial pressure of 597 mm Hg (PN2 of 597 torr).
This means that for the most part, our ventilations are moving mainly an
inert gas. This also allows for an easily changed ratio of gasses through the
administration of supplemental oxygen to increase the PO2 for respiratory
therapy. Nitrogen is the main gas found in the hollow gas-filled body
organs.
Carbon dioxide is only 0.3 mm Hg or 0.04%, an almost negligent
amount. H2O forms 3.7 mm Hg. For the most part, it is easier to think of
PO2 as 160 mm Hg., and PN2 of 600 mm Hg., with the total being 760 mm
Hg.
Respiration Control
Respiration is controlled through many mechanisms. The main
control mechanism is the respiratory center. It has both an inspiratory and
expiratory center, which act in an active passive rotational relationship.
Breathing is mainly an involuntary process that can be consciously altered
for a period of time. The respiratory centers override a person's conscious
influence, and resume normal function within a short period of time.
It is important to consider the various mechanisms for rhythmic
ventilation and for rate and depth of breathing. The inspiratory and
expiratory centers are located in the medulla and are responsible for the
basic rhythm of respiration. The inspiratory muscles, which are the
diaphragm and intercostal muscles, contract when stimulated by nerve
impulses that originate within the respiratory center neurons of the
medulla.
Inspiratory center neurons are spontaneously active and exhibit a
cyclical pattern of activity followed by fatigue and spontaneous activity
repeating. The expiratory center neurons are normally inactive during
quiet respiration They are stimulated when activity of the inspiratory
center increases during heavy or labored difficult breathing and
reciprocates with the inspiratory center, alternating a forceful inspiration
with a forceful expiration.
These neurons are chemoreceptors that respond to changes in blood
chemistry, mainly the hydrogen ion concentration resulting form the
carbon dioxide. As a lower concentration of oxygen occurs, a higher
concentration of carbon dioxide results which lowers the pH of the blood.
The chemoreceptors neurons of the respiratory center respond to this
initiating increased respirations, blowing off CO2 to correct the acid base
balance.
The respiratory center is also stimulated by an increase in body
temperature. This is an important fact to recall in patient assessment.
The mechanisms responsible for basic respiratory rhythm are the
Vagal, Hering-Breuer, reflex, and the pneumotaxic center.
Stretch receptors located mainly in the visceral pleura surrounding
the lungs are stimulated at the end expansion of the chest, sending
impulses to the respiratory center. This inhibits inspiration and initiates
expiration.
The pneumotaxic center sets up the coordination of the transition
between the inspiration phase and the expiration phase. It produces
inhibitory impulses limiting inspiration, thus tends to increase overall
respirations when active.
Ventilation
The actual movement of gasses in and out of the lungs is called
ventilation, the breathing that commonly is called respirations. Respiration
is the exchange of gasses between the cell and the environment, and
includes more than just the gas movement in and out of the lung.
Ventilation is the process of gas movement into and out of the lungs.
Pressure
Air, or the gasses, flow from an area of higher pressure or
concentration of atoms to an area of lower pressure or concentration of
atoms. A pressure gradient is required for the gas to flow into the lungs.
This pressure gradient is produced by differences in the atmospheric
pressure, the intrapulmonic pressure, and the intrapleural (intrathoracic)
pressure.
Recall that the total pressure of all the gasses in air at sea level
produces 760 mm Hg of pressure. This pressure does vary with altitude,
decreasing as one goes up from sea level.
To get the air to move in and out of the lungs, the intrapulmonic
pressure, which is the pressure of the gas in the alveoli, is increased and
decreased. This pressure varies with the changes in size of the thorax.
When the thorax increases in inspiration, the intrapulmonic pressure is
decreased, and the air moves into the lungs. When the thorax size is
decreased in expiration, the intrapulmonic pressure is increased and the
air moves out of the lungs. This varying pressure is only slightly above and
below 760 mm Hg.
Intrapleural pressure, which is the pressure in the pleural space, is
normally less than atmospheric pressure, usually 751-754 mm Hg. It is the
natural elastic recoil of the lungs that produces the increased
intrapulmonic pressure greater than atmospheric to expel the air from the
lungs. The intrapleural pressure may exceed atmospheric pressure during
coughing and forcing expiration.
Inspiration
Inspiration is an active process of muscle contraction and as such
requires energy.
First, the chest wall expands increasing the size of the thoracic cavity
and the lungs expand. As the lung space increases intrapulmonic pressure
drops to about 1 mm Hg below atmospheric pressure. A pressure gradient
is produced that causes gas to flow into the lungs. With the end inspiration
through the inhibitory process such as the stretch reflexes, the thorax
expansion stops and the alveoli stop expanding resulting in the
intrapulmonic pressure equaling the atmospheric pressure thus gas flow
no longer occurs and no more air enters lungs.
Expiration
Expiration is a passive process that is accomplished through the chest
wall relaxing. It is reverse of the process of inspiration. Here, the muscles
relax mainly with the diaphragm curving upward, and the natural force of
gravity acting on the rib cage with the elastic recoil causes the thorax and
lung space to decrease in size. A pressure gradient is created with the
intrapulmonic pressure increased above atmospheric pressure. The
intrapulmonic pressure about 1 mm Hg over atmospheric pressure and as
a result gas flow out of the lungs occurs.
At end inspiration, opposing forces and pressures become equal
because the thoracic volume no longer decreasing. The intrapulmonic
pressure equals atmospheric pressure and air movement out of the lungs
stops.
Muscles for Respiration
The diaphragm is the main muscle of respiration. Internal and
external intercostal muscles are also involved. The additional accessory
muscles of the sternocleidomastoid and scalenes may be used excessively
in respiratory difficulty. Using the accessory muscles is more work as it is
a voluntary action. Hyperinflation results in the need for forced expiration
resulting in more muscle usage, and thus increased work for breathing.
The diaphragm flattens and drops with contraction, increasing the
thoractic volume. With relaxation, it returns to the dome shape, decreasing
volume.
The Work of Breathing
The amount of energy required to breath is referred to as the work
of breathing. Normally it is low, only 3% of the total body energy needs in
normal healthy people.
The work of breathing, and consequently the energy requirement for
ventilation may be increased by the loss of the pulmonary surfactant, an
increase in the airway resistance, or a decrease in the pulmonary
compliance
Surfactant
Pulmonary surfactant lowers surface tension allowing for easier expansion
and prevents collapse of alveolus at end of expiration Decreases in
surfactant requires higher pressures to maintain lung expansion. Once
alveoli are collapsed or filled with fluid, higher pressures are required to
expand.
Airway Resistance
Compliance
Volumes
Tidal Volume
Dead Space
Expiratory reserve Volume
Lung capacities
Inspiratory capacity
Functional residual capacity
Vital capacity
Total lung capacity
Diffusion of Oxygen and Carbon Dioxide
Perfusion
2. Common disturbances of oxygenation (e.g., altered oxygen
intake and supply, altered oxygen absorption and
transportation, altered cellular demand for oxygen)
a. Developmental level: infancy through senescence
b. Individual preferences and patterns (e.g., smoking, sedentary
lifestyle)
c. Physical condition (e.g., breathing patterns, body weight, body
temperature, hemoglobin, exercise patterns)
d. Environmental factors (e.g., pollution, high altitudes, room ventilation,
air temperature changes, overcrowded conditions)
e. Psychological factors (e.g., stress, emotional status, anxiety)
4. Theoretical basis for interventions to promote oxygenation
a. Positioning (e.g., elevation of the extremities, Fowler's position)
b. Activity and rest patterns (e.g., passive and active exercise, stress
reduction)
c. Dietary modifications (e.g., sodium restriction, increased fluids, caloric
restriction, modifications to promote erythrogenesis)
d. Administration of oxygen (e.g., nasal cannula, mask, humidification)
e. Airway maintenance (e.g., coughing and deep breathing, cupping and
clapping, incentive spirometry, nasopharyngeal suctioning, pursed-lip
breathing, postural drainage)
B. Nursing care related to theoretical framework
1. Assessment: gather and synthesize data about the patient's
oxygenation status in relation to the patient's functional
health patterns
a. Obtain the patient's oxygenation history (e.g., dyspnea, fatigue,
altered sensation, occupation, health habits)
b. Assess factors affecting oxygenation (see III3A)
c. Obtain the objective data (e.g., respiratory rate and rhythm,
peripheral pulses, skin color, breath sounds, restlessness, tachycardia,
apnea, tachypnea, pallor, cyanosis, confusion, hypoventilation,
hyperventilation, airway patency, capillary refill)
d. Review laboratory and other diagnostic data (e.g., blood gases,
hemoglobin, hematocrit, sputum cultures, chest X ray, pulmonary
function studies, pulse oximetry)
e. Collect specimens
2. Analysis: identify the nursing diagnosis (patient problem)
and determine the expected outcomes (goals) for patient care
a. Identify nursing diagnoses (e.g., ineffective airway clearance related
to immobility, noncompliance with smoking cessation related to
physiological addiction, activity intolerance related to shortness of
breath)
b. Set priorities and establish expected outcomes (patient-centered
goals) for care (e.g., patient's breath sounds will be clear, patient will
enroll in a behavior modification program for smoking cessation, patient
will ambulate 200 feet without shortness of breath)
3. Planning: formulate specific strategies to achieve the
expected outcomes
a. Incorporate factors affecting oxygenation in planning the patient's
care (e.g., plan for humidification, ensure adequate ventilation, discuss
with parents the effects of secondary smoke, space activities to allow
for periods of rest) (see IIIA3)
b. Plan nursing measures on the basis of established priorities to help
the patient achieve the expected outcomes (e.g., established physical
activity program, plan coughing and deep-breathing regimen with the
patient, plan for frequent position changes, refer the patient to smoking
cessation programs in the community)
4. Implementation: carry out nursing plans designed to move
the patient toward the expected outcomes
a. Maintain oxygen intake and supply (e.g., assist with turning, deep
breathing, and coughing; perform nasopharyngeal suctioning; provide
cupping, vibrating, and postural drainage; administer oxygen via mask,
tent, and cannula; maintain a patent airway; increase fluid intake;
perform Heimlich maneuver; encourage the use of an incentive
spirometer)
b. Promote oxygen absorption and transport (e.g., encourage an
increased intake of dietary protein, iron, and vitamin C; encourage an
increase in exercise; promote good peripheral circulation by avoiding
constricting positions, clothing, and dressings, etc.)
c. Reduce cell demand for oxygen (e.g., promote rest, reduced anxiety,
encourage weight loss, prevent shivering)
d. Use safety measures related to oxygen therapy (e.g., enforce no-
smoking regulations, check electrical outlets)
e. Provide information and instruction regarding oxygenation (e.g.,
instruct the patient about the benefits of aerobic conditioning, provide
instruction regarding occupational exposure to pollutants)
5. Evaluation: appraise the effectiveness of the nursing
intervention relative to the nursing diagnosis and the
expected outcomes
a. Record and report patient's response to nursing actions (e.g., changes
in vital signs, alteration is skin colour, improvement in blood gas values,
increased or decreased alertness, improved tolerance for activities,
alterations in level of consciousness)
b. Reassess and revise the patient's plan for care as necessary (e.g.,
provide additional pillows for the patient who is experiencing
orthopnea)
