Differential Diagnosis

   The condition most commonly confuse with acute bronchiolitis is Asthma. One or more of the following favors the diagnosis of asthma : :A family history of asthma, repeated  episodes in the same infants, sudden on set without preceding infection, eosinophilia, and an immediate favorable response to the administration of a single dose of aerosolize albuterol. Repeated attacks represent an important differential point; fewer than 5% of recurrent attack of clinical bronchiolitis have viral infections as a cause. Other entities that may be confused with acute bronchiolitis are cystic fibrosis, heart failure, a foreign body in the trachea, pertussis, organophosphate poisoning, and bacterial bronchopneumonias associated with generalized obstructive pulmonary over inflation or in other words,on the chest radiograph bronchiolitis is associated with air trapping and hyperinflation with or without focal and patchy atelectasis, whereas pneumonia lacks signs of hyperinflation and is characterised by interstitial thickening

 Course and prognosis

                                      The most critical phase of illness occurs during the first 48-72hr after the onset of cough and dyspnea. During this period, the infant appears desperately ill, apneic spells occur in the very young infant, and respiratory acidosis is likely to be noticed. After the critical period, improvement occurs rapidly and often dramatically. Recovery is complete in a few days. The case fatality rate is less than 1%;death may result from prolonged apneic spells, severe uncompensated respiratory acidosis, or profound dehydration secondary to the loss of  water vapor from tachypnea and the inability to dring fluids.infants with conditions such as congenital heart disease, brochopulmonary dysplasia, immunodeficiency diseases, or cystic fibrosis have a greater morbidity rate and a slightly increased mortality rate. Estimates of mortality among infants with these high-risk conditions who contract RSV bronchiolitis decreased from 37% in 1982 to 3.5% in 1988. Bacterial complications, such as bronchopneumonia or sepsis, are uncommon. Otitis media may occur. Cardiac failur during bronchiolitis is rare, except in children with underlying heart desease so one should not mistake the palpability of liver because it due to the fact that the expanded lungs pushes the liver downward.

            A significant proportion of infants with bronchiolitis have hyperreactive airways during later childhood, but the relation of these entities, if any is not understood. The suggestion that a single episodes of bronchiolitis may result in long-term small airway abnormality requires further investigation. These abnormalities may be partially explained by the finding that infants with low total respiratory conductance are more likely to acquire bronchiolitis in response to viral respiratory infection. The infants with bronchiolitis in whom reactive airways develop are more likely to have a family history of asthma and allergy, a prolonged acute episode of brochiolitis, and exposure to cigarette smoke.

                   RSV immune globulin intravenous (RSV-IGIV) or intramuscularly administered monoclonal antibody to RSV (palivizumab) given just prior to and during RSV season is effective in preventing severe RSV disease in at risk infants. It is recommended for infants less than two yr with chronic lung disease (bronchopulmonary dysplasia) or prematurity but should not be given to those with symptomatic cyanotic congenital heart disease because of increasesd complications, including increased mortality. People having respiratory problems should avoid kissing or getting so closed to the infants unless the are free from the disease. smoking should be strictly avoided at least ,when near the infant.

Infants with Respiratory Distress should be hospitalized with the intention of giving supportive treatment i.e keeping child in a comparably cold atmosphere so that insensible water loss due to techypnea could be controlled and sufficient supply of Oxygen is also mandatory. One should not rely merely on cynosis for giving Oxygen as it is not in all the cases a reliable source of detecting arterial PO2 . I.V line should be maintained and parenteral fluids started.   

Recent Guidelines for Treatment

Antiviral treatment

Respiratory syncytial virus

Ribavirin aerosol is not effective in immune competent patients and is restricted to immunocompromised patients with severe respiratory syncytial virus disease, although this practice is not supported by randomised controlled trials

Parainfluenza virus and adenovirus

• No specific treatment is available
  
• Ribavirin has been used in immunodeficient patients, although this is mainly based on case reports and small series of heterogeneous patient populations.

Influenza virus

• Ribavirin aerosol is not effective in immunocompetent patients, and its efficacy in immunodeficient patients is unclear
  
• Oral amantadine and rimantadine (M2 protein inhibitors) have been shown to shorten disease by one day in adults and children over 1 year of age with influenza A when given within 48 hours of the start of symptoms
• Nasal zanamivir and oral oseltamivir (neuraminidase inhibitors) are effective in preventing and treating influenza A and B in adults
  
• Oseltamivir is also beneficial in children aged 1-12 years
  
• The neuraminidase inhibitors are preferred to the M2 inhibitors as they have a broader antiviral activity, have less tendency for the development of resistance, and are better tolerated

Antibiotics

Antibiotics do not influence the course of viral lower respiratory tract infection.

1. Nelson Textbook of Paediatrics (Behrman,Kliegman,,Jenson)Vol:2 16th Edition.J B M 
2. J.B.M Van Woensel, Viral lower respiratory tract infection in infants and young     children,BMJ  2003;327:36-40 (5 July)
   
3. Shay DK, Holman RC, Newman RD, Liu LL, Stout JW, Anderson LJ. Bronchiolitis-associated hospitalizations among US children, 1980-1996. JAMA 1999;282: 1440-6.

(note):    Human metapneumovirus
Human metapneumovirus has recently been identified as a new paramyxovirus causing respiratory tract infections. It was isolated from nasopharyngeal aspirates from 28 children with symptoms of lower respiratory tract infection in the winter season in the Netherlands. Further serological studies revealed that virtually all children have been exposed to the virus by the age of 5 years. Studies from several other countries have confirmed its role in respiratory infections in both children and adults^. The exact impact and epidemiology of human metapneumovirus in respiratory infections in infants and young children needs to be determined in prospective studies.