AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Bronchiolitis is an acute inflammatory injury of the bronchioles that is usually caused by a viral infection. Although it may occur in persons of any age, severe symptoms are usually only evident in young infants; the larger airways of older children and adults better accommodate mucosal edema. Bronchiolitis usually affects children younger than 2 years, with a peak in infants aged 3-6 months. Acute bronchiolitis is the most common cause of lower respiratory tract infection in the first year of life. It is generally a self-limiting condition and is most commonly associated with respiratory syncytial virus.

Bronchiolar injury and the consequent interplay between inflammatory and mesenchymal cells can lead to diverse pathological and clinical syndromes. Bronchioles are small airways, less than 2 mm in diameter, and lack cartilage and submucosal glands. The terminal bronchiole, a 16th generation airway, is the final conducting airway that terminates in the respiratory bronchioles. The acinus (ie, the gas exchange unit of the lung) consists of respiratory bronchioles, the alveolar duct, and alveoli. The bronchiolar lining consists of surfactant-secreting Clara cells and neuroendocrine cells, which are the source of bioactive products such as somatostatin, endothelin, and serotonin.

Wilhelm Lange first described obliterative bronchiolitis (OB) in 1901 by reporting 2 cases of interstitial bronchiolar disorder. In 1985,¹ bronchiolitis obliterans-organizing pneumonia (BOOP) was described as a separate condition with different clinical, radiographic, and prognostic features than OB. BOOP is a histopathologic lesion, not a specific diagnosis. Its pathologic hallmark is proliferative bronchiolitis or bronchiolitis obliterans in association with organizing pneumonia. BOOP and OB are beyond the scope of this article and are not discussed further.

Pathophysiology

Bronchiolitis is very contagious. The virus that causes it is spread from person to person by direct contact with nasal secretions, airborne droplets, and fomites.

The effects of bronchiolar injury include the following:

• Increased mucus secretion
• Bronchial obstruction and constriction
• Alveolar cell death, mucus debris, viral invasion
• Air trapping
• Atelectasis
• Reduced ventilation that leads to ventilation/perfusion mismatch
• Labored breathing

Ninety percent of cases are caused by respiratory syncytial virus (RSV). Other causes of bronchiolitis are addressed in Causes. Complex immunologic mechanisms play a role in the pathogenesis of RSV bronchiolitis. Type 1 allergic reactions mediated by immunoglobulin E may account for some clinically significant bronchiolitis. Infants that are breastfed with colostrum rich in immunoglobulin A appear relatively protected from bronchiolitis.

Frequency

United States

Approximately 1 in 9 infants contracts bronchiolitis in the first year of life, usually during the fall and winter months.

In one study, an estimated 1.65 million hospitalizations for bronchiolitis occurred among children younger than 5 years from 1980-1996, accounting for 7 million inpatient days.² Children younger than 6 months accounted for 57% of these hospital visits; those younger than 1 year accounted for 81%.

International

According to the World Health Organization bulletin,³ an estimated 150 million new cases occur annually; 11-20 million (7-13%) of these cases are severe enough to require hospital admission. Worldwide, 95% of all cases occur in developing countries.

Mortality/Morbidity

Acute respiratory tract infection in children younger than 5 years is still the leading cause of childhood mortality in the world. In 2000, acute respiratory tract infection accounted for an estimated 1.9 million deaths worldwide; 70% of these deaths occurred in Africa and Southeast Asia.

Race

Race and low socioeconomic status may adversely affect outcome in patients with acute bronchiolitis. In one study,⁴ RSV bronchiolitis seemed to be more severe in white children than in black children. The reason for this finding is unknown. A study by La Via et al⁵ demonstrated that although more minority children than white children were hospitalized with RSV infection, nothing indicated that the infections in minority children were more or less severe than those in white children.

Sex

The incidence of bronchiolitis is slightly higher in boys. The exact etiology is unclear.

Age

Age was found to be a significant factor in the severity of infection. The younger the person, the more severe the infection tended to be, as measured by the lowest oxygen saturation. Infants younger than 6 months are most severely affected, owing to smaller, more easily obstructed airways and a decreased ability to clear secretions.

Intrauterine cigarette-smoke exposure may impair in utero airway development or alter the elastic properties of the lung tissue. Second-hand cigarette smoke (eg, by a parent or family member) in the postnatal period compounds the severity of RSV bronchiolitis in infants.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Profuse coryza, congestion, pharyngitis, nasal discharge, and fever usually characterize the clinical syndrome in children. Primary RSV infections are confined to the upper airways in more than 50% of patients. Symptoms reach a peak in 2-5 days, with involvement of the lower respiratory tract. Typical symptoms include the following:

• Cough
• Dyspnea
• Wheezing
• Poor feeding
• Hypothermia or hyperthermia

Physical

Physical findings for bronchiolitis are not restricted to the airway. They may include the following:

• Hypothermia or hyperthermia
• Otitis media
• Tachypnea
• Nasal flaring
• Intercostal retractions
• Irritability
• Fine rales
• Wheezing
• Hypoxia

Causes

RSV is the most commonly isolated agent. It is found in 75-90% of children younger than 2 years who are hospitalized for bronchiolitis. Abundant evidence suggests that complex immunologic mechanisms play a role in the pathogenesis of RSV bronchiolitis. Type I allergic reactions mediated by the immunoglobulin E antibody may account for clinically significant bronchiolitis. Babies breastfed with colostrum rich in immunoglobulin A appear relatively protected from bronchiolitis.

Other agents that cause bronchiolitis include the following:

• Parainfluenza virus types 1, 2, and 3
• Influenza B
• Echovirus
• Rhinovirus
• Adenovirus types 1, 2, and 5: These viruses cause bronchiolitis obliterans, a particularly destructive type of bronchiolitis.
• Mycoplasma: Bronchiolitis from this cause primarily occurs in school-aged children.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Bronchiolitis obliterans-organizing pneumonia
Congestive Heart Failure
Constrictive bronchiolitis
Croup
Cystic Fibrosis
Pertussis

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

The diagnosis of bronchiolitis is based on clinical presentation, the patient's age, seasonal occurrence, and findings from the physical examination. Tests are typically used to exclude other diagnoses, such as bacterial pneumonia, sepsis, or congestive heart failure, or to confirm a viral etiology and determine required infection control for patients admitted to the hospital. Although the use of diagnostic tests is common, several investigators argue that these should not be routinely performed, citing concerns about costs, inappropriate use of antibiotics, and the lack of proven benefit. In reality, few studies exist that critically evaluate the utility of diagnostic tests for this disease. Some hospitals have developed protocols or guidelines on testing and management, while others have left the decision entirely to the treating physician.

From a survey of hospital-based pediatricians, the most common tests are rapid viral antigen testing of nasopharyngeal secretions for RSV, blood gas analysis, WBC count with differential, C-reactive protein (CRP) level, and chest radiography. Other common tests are pulse oximetry, blood culture, urine analysis and culture, and cerebrospinal fluid analysis and culture.

WBC count and differential

This is commonly performed to look for coexisting bacterial infection, but few studies have evaluated its utility for this purpose. Case reports have described patients with bronchiolitis who had elevated WBC counts that prompted further evaluation and eventual identification of a bacterial pathogen. In one study of 120 infants infected by RSV, Saijo et al⁶ demonstrated a correlation between an elevated WBC count and a radiographic pattern of lobar pneumonia when compared with a pattern of bronchopneumonia or bronchiolitis. CRP levels and erythrocyte sedimentation rate followed the same pattern in this study. Veira et al⁷ also observed an association between a viral etiology and low WBC count and CRP level during initial and follow-up testing.

The WBC count has been decried for its poor test characteristics. Among infants with a febrile illness, WBC values are highly variable. In a study of febrile neonates who received a septic workup, WBC counts overlapped substantially between the groups with bacterial infection, viral infection, pneumonia, and workup negative for sepsis. No WBC count threshold had good discriminatory value for the presence of bacterial infection.

No strong evidence supports a recommendation for or against WBC testing in patients with bronchiolitis. 

Septic workup

In most patients with RSV bronchiolitis, especially those with mild disease, the risk of serious secondary bacterial infection is low. In 2 retrospective studies of children who presented with lower respiratory tract infection with RSV, positive culture results were found in 1.2% and 1.6% of children tested, respectively. However, serious bacterial infections can occasionally occur, so the importance of evaluating patients with fever and bronchiolitis remains controversial.

A study of 90 newborns with bronchiolitis, pneumonia, or both noted that among the few who appeared very sick upon presentation or had a prolonged clinical manifestation, a bacterial infection was frequently associated. Kuppermann et al⁸ found no evidence of bacteremia in 156 patients with bronchiolitis aged younger than 24 months; patients with lobar consolidation were excluded. Liebelt et al⁹ studied infants aged 90 days or younger with bronchiolitis and noted a low risk of serious bacterial infection and wide variability in the use of diagnostic tests in this population.

When febrile infants aged 1-90 days were stratified into high- or low-risk groups based on the Rochester criteria, patients who were RSV positive and at high risk had significantly fewer bacterial infections than patients who were RSV negative and at high risk (5.5% vs 16.7%). The rate of bacteremia in the high-risk, RSV-positive group was similar to that in the low-risk, RSV-negative group. In fact, introducing RSV rapid antigen testing in the evaluation of febrile children at a single center decreased the use of antibiotics, the duration of use of antibiotics, and the number of prescriptions of antibiotics upon discharge. Therefore, RSV testing should be universally implemented during the RSV season.

In conclusion, RSV testing is commonly practiced and has good utility. Although an argument is that it has little influence on outcome, RSV testing does influence treatment because physicians appear likely to withhold antibiotics or to stop them sooner in patients who are RSV positive. RSV testing can also be used to isolate patients who are RSV positive and to categorize patients for cohort nursing.
 
Pulse oximetry

Pulse oximetry is measured in almost every child who presents with acute bronchiolitis. Suggested guidelines for lower limits of acceptable oxygen saturation levels for bronchiolitis include 90%, 92%, and 94%. In some studies, oxygen saturation levels of less than these values predicted subsequent deterioration. Emergency department pediatricians are approximately twice as likely to recommend hospitalization when the oxygen saturation level is 92% as when it is 94%.

In previously healthy infants with bronchiolitis who deteriorated in the hospital and required PICU transfer, the mean oxygen saturation level at presentation was 88% (compared with 93% in matched controls). In addition, an oxygen saturation level of 85% or less and a respiratory rate of greater than 80 respirations per minute at presentation each had a specificity of 97% but a sensitivity of 30% or less in predicting subsequent deterioration.

However, increased reliance on the oxygen saturation level, by lowering its admission threshold, may have contributed to the significantly reported increase (nearly 250%) in the hospitalization rate for children with bronchiolitis since the 1980s. A review of the medical records of previously healthy children admitted with bronchiolitis revealed that hospital discharge was delayed based on pulse oximetry values when the patients were otherwise stable for discharge. This was associated with significant cost implications. The variations in the oxygen saturation levels in healthy infants have been reported.

The implications of a particular oxygen saturation level may vary depending on whether the level is determined upon admission in a child who is sick or upon discharge in a child who is otherwise stable. More research is needed to identify the minimum threshold oxygen saturation level at which patients can be safely discharged.
 
Nasopharyngeal aspirate
 
Testing for RSV based on nasopharyngeal aspirate is common but may not change the outcome. The test is performed mainly to make a definitive diagnosis. Viral culture for RSV is considered the criterion standard; however, several immunologic tests are more convenient, faster, and less costly. These tests are performed by either direct IFA staining or by ELISA. IFA requires approximately 2-6 hours and is 90% sensitive and specific, whereas ELISA requires 30 minutes for processing and is 85-90% sensitive.

Imaging Studies

Chest radiography

Radiologic findings in individuals with bronchiolitis are variable and may include bronchial wall thickening, tiny nodules, linear opacities, atelectasis, patchy alveolar opacities, and lobar consolidation.

Among 153 children with acute bronchiolitis, Dawson et al¹² found no correlation between the degree of change on the chest radiograph and a clinical scoring method. However, in Shaw's 1991 study¹³ of 213 infants with bronchiolitis, atelectasis was 2.7 times more likely to be found at presentation in the patients with severe disease than in those with mild disease. One survey showed that chest radiographs were obtained 83% of the time in patients with bronchiolitis, while antibiotics were prescribed only 69% of the time. These results likely indicate that physicians withhold antibiotics if no infiltrate is visible on the radiograph of the patient with bronchiolitis.

Finding an infiltrate, however, does not necessarily imply a bacterial etiology. In a study reported in 1990 of 128 infants and children aged 7 years or younger, Friis et al¹⁴ identified 76 patients with bronchiolitis. Thirty-seven of these patients had pathogenic bacteria in their respiratory tract. The chest radiograph showed no abnormality significantly more often in the virus-positive, bacteria-negative group. However, lobar or segmental consolidation was equally likely in those with or without a bacterial pathogen. Therefore, although a radiograph with negative findings may have some value, children who do not appear ill are unlikely to have a radiograph that shows abnormalities. A practical approach is to obtain a chest radiograph in children who appear ill, experience clinical deterioration, or are at high risk, such as those with an underlying cardiac or pulmonary disease.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

Most cases of bronchiolitis result from a viral pathogen such as RSV, parainfluenza virus, influenza virus, or adenovirus. Approximately 123,000 infants are hospitalized each year for bronchiolitis. Of the total number of hospitalizations from 1980-1996 involving lower respiratory tract illnesses in infants younger than 1 year, the proportion of infants hospitalized for bronchiolitis more than doubled, from 22.2% to 47.4%. RSV is responsible for most admissions involving bronchiolitis. Eighty-one percent of all children hospitalized for bronchiolitis are younger than 1 year; 57% are younger than 6 months. RSV infection accounts for 500 deaths each year.

In many children, RSV bronchiolitis is a self-limited disease and can be safely managed in an outpatient setting. However, disease manifestation can be variable, and risk factors for severe disease include preexisting cardiac or pulmonary disease, premature birth, very young age (<2-3 mo), nosocomial RSV infection, and, in some studies, low socioeconomic status.

Despite the increasing hospitalization rate, controversy still exists regarding the optimal treatment of these patients. As a result, the use of management tools among physicians and between hospitals varies greatly. The use of clinical practice guidelines can standardize care, reduce admissions, manage resources better, and shorten the length of hospital stays without increasing re-admission rates or decreasing family satisfaction.

Management is primarily supportive and should focus on therapies that improve oxygenation and hydration. Management strategies to consider include the following:

• Importantly, carefully assess clinical respiratory status and the severity of disease.
• Measure the oxygen saturation level. Use supplemental humidified oxygen, if necessary, to maintain adequate oxygen saturation.
• Consider bronchodilator therapy to relax bronchial smooth muscle. Although this treatment is common, no convincing evidence supports it as routine practice. Consider continuing bronchodilator therapy in patients who demonstrate clinical improvement.
• Maintain adequate hydration. Parenteral therapy may be necessary in patients who are unable to take fluids by mouth or who have a respiratory rate of greater than 70 respirations per minute. Patients with apneic episodes should have access to intravenous hydration.
• Institute respiratory and contact isolation precautions to prevent nosocomial transmission.
• Confirm the viral etiology based on rapid antigen testing of the nasopharyngeal aspirate. Positive viral antigen test results indicate that a concomitant serious bacterial infection is unlikely and are strongly indicative to the physician to withhold empiric antibiotic drugs.
• In previously healthy children with viral bronchiolitis, a chest radiograph, CBC count, or blood culture is not necessary. However, give careful consideration to these tests in persons with severe disease or a very ill appearance, preexisting cardiac or pulmonary disease, a markedly elevated temperature, or other risk factors for more severe disease.
• A few children at risk for acute respiratory failure may require monitoring of the blood carbon dioxide level.
• Decide whether the patient should be treated in an inpatient or outpatient setting.
• For outpatients, review discharge instructions carefully and arrange for appropriate follow-up with the primary care physician.
• Electronic cardiac and respiratory monitoring is required for some patients (persons who are very sick, are very young, or are having apneic episodes). This monitoring should be discontinued in a timely manner when it is no longer necessary.
• Determine whether an infant with bronchiolitis should be admitted. For hospitalized patients, the length of stay averages 2-3 days, with a re-admission rate of 1-4%. Infants with bronchiolitis at increased risk should be considered for admission. Conditions for increased risk include the following:
• • Congenital heart disease, especially if associated with cyanosis or pulmonary hypertension
  • Chronic lung disease, especially if the patient is on supplemental oxygen
  • Prematurity
  • Age younger than 3 months, when severe disease is most common
  • Oxygen saturation level of 92% or less
  • Respiratory rate of greater than 70-80 respirations per minute
  • Difficulty feeding due to respiratory distress
  • Less serious conditions (eg, neuromuscular disease, history of recurrent aspiration, congenital anomaly of the airway, myasthenia gravis, immunodeficiency state)

• Determine which patients need to be admitted to the ICU. Criteria for ICU admission vary greatly among physicians. ICU admission is uncommon for previously healthy infants who present with bronchiolitis (1.8% of 542 patients in one study). Patients with the following conditions should be evaluated for PICU admission:
   
  
  • Worsening hypoxemia or hypercapnia
  • Apnea
  • Worsening respiratory distress
  • Worsening mental status
• Determine criteria for patient discharge. The median duration of cough, poor sleeping and irritability, wheezing, and poor feeding is 7-12 days. Further research is needed to clarify safe endpoints for discharge. Criteria currently in use include the following:
  
  
  • Clinical improvement
  • Oral intake adequate to maintain hydration status
  • No apnea in preceding 24 hours in infants younger than 6 months or preceding 48 hours in patients older than 6 months
  • Acceptable oxygen saturation for more than one day, either on room air or from stable oxygen therapy of less than 0.5 L/min by nasal canula
  • Respiratory rate less than 80 respirations per minute
  • When appropriate, home oxygen therapy arranged and patient or parents educated in its use
  • Follow-up arranged with primary care physician

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Treatment is mainly supportive and should consist of supplemental humidified oxygen, fluids, and optional bronchodilator therapy. The most important therapy is humidified oxygen.

Medications have a limited role in the management of bronchiolitis. Several drugs are commonly used, but little or inconclusive evidence supports the routine use of any drug in the management of bronchiolitis.

Some patients have abnormal changes on their chest radiographs. Ascribing the abnormality to a bacterial or viral infection should be based on factors pertinent to each patient.

In patients who are febrile, have bronchiolitis, and are at high risk, including those with nosocomial RSV infection or who appear toxic at presentation, the rate of secondary bacterial infection is increased but small. The decision to start antibiotics should be individualized.

Older studies of nebulized epinephrine had indicated superior benefit in comparison with the beta-agonist albuterol (Salbutamol). Menon et al¹⁵ showed that infants treated with nebulized epinephrine in the emergency department have a lower hospitalization rate than those treated with albuterol (Salbutamol). A study that measured combined pulmonary and upper airway resistance in infants with bronchiolitis reported that resistance was reduced with epinephrine in comparison to albuterol (Salbutamol). This improvement in resistance may be related to the effects of epinephrine on the upper airway because some infants with bronchiolitis have nasal coryza and edema. When used in patients with bronchiolitis who required mechanical ventilation, improvement in respiratory system resistance was still demonstrable, but without any improvement of oxygenation or ventilation indices. However, several of these studies involved only a small number of patients.

More recently, a large multicenter, randomized, double-blinded, placebo-controlled study¹⁶ of hospitalized infants demonstrated no benefit of nebulized epinephrine regarding length of hospital stay, time until ready for discharge, or other secondary endpoints. Based on the findings of this study, the routine use of nebulized epinephrine cannot be recommended for patients with acute bronchiolitis.

Drug Category: Bronchodilators

This is one of the most commonly used therapies. Studies have reported that the use of bronchodilators varies from approximately 50% to more than 90%. Most controlled studies have failed to show a benefit in terms of oxygen saturation, rate of hospitalization, or length of hospital stay, but some studies have demonstrated an improvement in short-term surrogate measures. Bronchiolitis and asthma have similar symptoms and signs, and some concern exists that patients with asthma could be misdiagnosed with bronchiolitis. The pathology of bronchiolitis involves edema of the airway wall rather than bronchoconstriction, as in asthma. Although the use of bronchodilators in patients with bronchiolitis remains widespread, no convincing evidence supports this approach as routine practice. One practical approach is to continue the use of bronchodilators only in patients who demonstrate clinical improvement.

Drug Category: Corticosteroids

Several placebo-controlled trials of corticosteroid therapy in different formulations did not show any benefit for important outcomes such as duration of hospitalization or time to resolution of clinical symptoms. In one study, 8-61% of patients who presented to several hospitals were treated with corticosteroids. Administering inhaled budesonide for 2 wk to infants with acute bronchiolitis conferred no short- or long-term clinical benefit in comparison with placebo. In addition, an 8-wk course of budesonide by metered-dose inhaler in a placebo-controlled study was not beneficial on postbronchiolitis coughing and wheezing up to 12 mo later. A recent double-blind, randomized trial¹⁷ comparing a single dose of oral dexamethasone (1 mg/kg body weight) with placebo in 600 children with moderate-to-severe bronchiolitis revealed no change in hospital admission, length of hospital stay, or subsequent admissions.

Parenteral corticosteroid treatment in comparison with placebo was also not beneficial in patients mechanically ventilated for RSV lower respiratory tract infection for the endpoints of duration of mechanical ventilation, length of stay in the PICU and the hospital, and the duration of oxygen supplementation. However, a post hoc analysis suggested that corticosteroid therapy reduced the duration of mechanical ventilation and oxygen supplementation in the subset of patients with bronchiolitis. Additional studies are needed to support this finding.

Drug Category: Antiviral drugs

Ribavirin is licensed by the US Food and Drug Administration for the management of RSV bronchiolitis and pneumonia, but clinically relevant benefit has been difficult to demonstrate. Early studies showed that it can reduce RSV titers in nasopharyngeal secretions. When used, it has usually been in children with bronchiolitis at high risk. However, placebo-controlled studies have not reproduced clinical benefit. In one multicenter placebo-controlled study of infants admitted for bronchiolitis with risk factors for severe disease, ribavirin demonstrated a lack of clinical effectiveness. Long-term follow-up studies of ribavirin have not consistently shown a benefit to pulmonary function. Given its high cost and lack of proven benefit, its use is difficult to justify.

Drug Category: Respiratory agents

Healthy children with bronchiolitis usually have limited disease. These patients usually do well with supportive care only.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Admission criteria
• • Oxygen requirement
  • Severe retractions
  • Tachypnea
  • Inability to tolerate oral fluids
  • Apnea
  • Immunocompromise
  • Severe underlying cardiopulmonary disease

Further Outpatient Care

• Discharge criteria
• • Acceptable oxygen saturation
  • Ability to self-hydrate
  • Adequate follow-up within 24 hours

Deterrence/Prevention

• Most cases of bronchiolitis are not readily preventable because the viruses responsible are ubiquitous. However, careful attention to frequent hand washing, especially around infants, can aid in the prevention of infection or spread of viruses.

Complications

• Most previously healthy children with bronchiolitis recover with few complications, but the resolution of symptoms may take weeks. Follow-up should be arranged with the primary care physician. Among those with severe disease, a few may develop respiratory failure and experience a protracted hospital course. Some patients will require supplemental home oxygen therapy at the time of discharge. On follow-up, these patients should be evaluated to document resolution of the need for oxygen therapy. An association between RSV bronchiolitis and subsequent wheezing and asthma has been noted, but proof of causality is lacking at present. Parental education is an important part of discharge planning.

Prognosis

• Bronchiolitis is an infectious, self-limited disease. Its therapy is based on supportive care, oxygenation, hydration, and fever control. With early recognition and treatment, prognosis is usually very good. Some infants who recover from acute bronchiolitis have an increased frequency of recurrent wheezing.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Misdiagnosis or delayed diagnosis, delay in treatment, inadequate follow-up

Special Concerns

Bronchiectasis after bronchiolitis 

Long-term pulmonary sequelae after RSV bronchiolitis are uncommon and may include subsequent wheezing. However, with adenoviral infection, severe lung damage, bronchiectasis, and hyperlucent lungs may result. Bronchiectasis after bronchiolitis is uncommon but has been described, with many reports implicating adenovirus. Adenovirus is a known cause of bronchiectasis after several childhood infections, especially with adenovirus types 3, 7, and 21. Bronchiectasis has also been noted after bronchiolitis in patients co-infected with RSV and adenovirus. In this setting, adenovirus is believed to be the causative factor, given its propensity to cause bronchiectasis.
 
One hypothesis is that long-term outcomes after infections with these different pathogens vary as a result of the differences in the immune response they elicit. Higher levels of interferon gamma, higher levels of soluble CD 25, and lower levels of soluble tumor necrosis factor receptor II have been observed with primary adenoviral infection in comparison with RSV infection in infants. An imbalance in the TH1/TH2 ratio has also been observed, with the ratio favoring TH1 in adenoviral infections and TH2 in RSV infections. The symptoms and treatment of bronchiectasis after bronchiolitis is similar to that in other settings.

Immunoglobulins and bronchiolitis

Recurrent respiratory infections, including bronchiolitis, have been reported in children with immunoglobulin A and/or immunoglobulin G subclass deficiency. In one report of 225 children aged 6 months to 6 years with recurrent sinopulmonary infections, the overall frequency of antibody defects was 19.1%. Immunoglobulin A and/or immunoglobulin G subclass deficiency was found in 25% of patients with recurrent upper respiratory tract infections, 22% of patients with recurrent pulmonary infections, and 12.3% of patients with recurrent bronchiolitis.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Epler GR, Colby TV, McLoud TC, Carrington CB, Gaensler EA. Bronchiolitis obliterans organizing pneumonia. N Engl J Med. Jan 17 1985;312(3):152-8. [Medline].
2. Shay DK, Holman RC, Newman RD, Liu LL, Stout JW, Anderson LJ. Bronchiolitis-associated hospitalizations among US children, 1980-1996. JAMA. Oct 20 1999;282(15):1440-6. [Medline].
3. Rudan I, Tomaskovic L, Boschi-Pinto C, Campbell H. Global estimate of the incidence of clinical pneumonia among children under five years of age. Bull World Health Organ. Dec 2004;82(12):895-903. [Medline].
4. Bradley JP, Bacharier LB, Bonfiglio J, Schechtman KB, Strunk R, Storch G, et al. Severity of respiratory syncytial virus bronchiolitis is affected by cigarette smoke exposure and atopy. Pediatrics. Jan 2005;115(1):e7-14. [Medline].
5. La Via WV, Grant SW, Stutman HR, Marks MI. Clinical profile of pediatric patients hospitalized with respiratory syncytial virus infection. Clin Pediatr (Phila). Aug 1993;32(8):450-4. [Medline].
6. Saijo M, Ishii T, Kokubo M, Murono K, Takimoto M, Fujita K. White blood cell count, C-reactive protein and erythrocyte sedimentation rate in respiratory syncytial virus infection of the lower respiratory tract. Acta Paediatr Jpn. Dec 1996;38(6):596-600. [Medline].
7. Vieira RA, Diniz EM, Vaz FA. Clinical and laboratory study of newborns with lower respiratory tract infection due to respiratory viruses. J Matern Fetal Neonatal Med. May 2003;13(5):341-50. [Medline].
8. Kuppermann N, Bank DE, Walton EA, Senac MO, McCaslin I. Risks for bacteremia and urinary tract infections in young febrile children with bronchiolitis. Arch Pediatr Adolesc Med. Dec 1997;151(12):1207-14. [Medline].
9. Liebelt EL, Qi K, Harvey K. Diagnostic testing for serious bacterial infections in infants aged 90 days or younger with bronchiolitis. Arch Pediatr Adolesc Med. May 1999;153(5):525-30. [Medline].
10. Antonow JA, Hansen K, McKinstry CA, Byington CL. Sepsis evaluations in hospitalized infants with bronchiolitis. Pediatr Infect Dis J. Mar 1998;17(3):231-6. [Medline].
11. Bloomfield P, Dalton D, Karleka A, Kesson A, Duncan G, Isaacs D. Bacteraemia and antibiotic use in respiratory syncytial virus infections. Arch Dis Child. Apr 2004;89(4):363-7. [Medline].
12. Dawson KP, Long A, Kennedy J, Mogridge N. The chest radiograph in acute bronchiolitis. J Paediatr Child Health. Aug 1990;26(4):209-11. [Medline].
13. Shaw KN, Bell LM, Sherman NH. Outpatient assessment of infants with bronchiolitis. Am J Dis Child. Feb 1991;145(2):151-5. [Medline].
14. Friis B, Eiken M, Hornsleth A, Jensen A. Chest X-ray appearances in pneumonia and bronchiolitis. Correlation to virological diagnosis and secretory bacterial findings. Acta Paediatr Scand. Feb 1990;79(2):219-25. [Medline].
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Article Last Updated: Sep 7, 2007