eMedicine Specialties > Emergency Medicine > Pediatric

Pediatrics, Bronchiolitis

Author: Mark Louden, MD, FACEP, Assistant Medical Director, Emergency Department, Duke Raleigh Hospital
Contributor Information and Disclosures

Updated: Jun 23, 2009

Introduction

Background

Bronchiolitis is an acute infectious disease of the lower respiratory tract that occurs primarily in young infants, most often in those aged 2-24 months.

Pathophysiology

Bronchiolitis is usually due to a viral infection of the small airways (bronchioles). Infection of bronchiolar respiratory and ciliated epithelial cells produces increased mucus secretion, cell death, and sloughing, followed by a peribronchiolar lymphocytic infiltrate and submucosal edema. The combination of debris and edema produces critical narrowing and obstruction of small airways.

Decreased ventilation of portions of the lung causes ventilation/perfusion mismatching, resulting in hypoxia. During the expiratory phase of respiration, further dynamic narrowing of the airways produces disproportionate airflow decrease and resultant air trapping. Work of breathing is increased due to increased end-expiratory lung volume and decreased lung compliance. Recovery of pulmonary epithelial cells occurs after 3-4 days, but cilia do not regenerate for about 2 weeks. The debris is cleared by macrophages.

Infection is spread by direct contact with respiratory secretions. In the United States, epidemics last 2-4 months beginning in November and peaking in January or February. While 93% of cases occur between November and early April, sporadic cases may occur throughout the year. Attack rates within families are as high as 45% and are higher in daycare centers. Rates of hospital-acquired infection range from 20-47%. Previous infection with the common etiologic viruses does not confer immunity. Reinfection is common.

Frequency

United States

Annual incidence is 11.4% in children younger than 1 year and 6% in those aged 1-2 years. The illness accounts for 4500 deaths and 90,000 hospital admissions per year. Prevalence may be higher in urban areas.

In children aged 2 years, approximately 95% have serologic evidence of past infection with the predominant causative agent, respiratory syncytial virus (RSV). Unfortunately, presence of antibodies to RSV does not confer immunity.

International

RSV is an important respiratory pathogen worldwide. The frequency of bronchiolitis in developed countries appears to be similar to that in the United States. Epidemiologic data for underdeveloped countries are incomplete. Peak incidence of bronchiolitis usually occurs during winter months in temperate climates and during the rainy season in tropical climates. In the United States, the peak occurs in February. Morbidity and mortality may be higher in less developed countries because of poor nutrition and lack of resources for supportive medical care.

Mortality/Morbidity

Significant morbidity is unusual.

  • Hospitalization is required in up to 2% of cases; most of those patients are younger than 6 months. These patients account for as many as 17% of all infant hospitalizations. Hospitalization is significantly more likely at altitudes above 2500 meters (8000 ft). Mechanical ventilation is required for 3-7% of admitted patients.
  • The mortality rate is 1-2% of all hospitalized patients and 3-4% for patients with underlying cardiac or pulmonary disease.
  • Most deaths occur in infants younger than 6 months.

Race

  • Race and socioeconomic status may affect the frequency of contracting bronchiolitis.
  • Lower socioeconomic status may increase the likelihood of hospitalization. Hospitalization rates are higher in Native American, Alaskan, and Hispanic populations, but it is not clear if this is due to more severe infection or a lower threshold for admission.

Sex

Bronchiolitis occurs as many as 1.25 times more frequently in males than in females.

Age

  • Although infection with etiologic agents may occur at any age, the clinical entity of bronchiolitis includes only infants and young children. Seventy-five percent of cases of bronchiolitis occur in children younger than 1 year, and 95% in children younger than 2 years. Incidence peaks in those aged 2-8 months.

Clinical

History

  • History and physical examination form the primary basis for the diagnosis of bronchiolitis.
  • Early symptoms are those of a viral upper respiratory tract infection (URI), including mild rhinorrhea, cough, and sometimes low-grade fever.
  • Adults, older children, and many infants do not progress beyond this stage of URI.
  • For the 40% of infants and young children who progress to lower respiratory tract involvement, paroxysmal cough and dyspnea develop within 1-2 days.
  • Other common symptoms include the following:
    • Fever
    • Increased work of breathing
    • Wheezing
    • Cyanosis
    • Grunting
    • Noisy breathing
    • Vomiting, especially post-tussive
    • Irritability
    • Poor feeding or anorexia

Physical

Most patients with bronchiolitis have the following signs:

  • Tachypnea, often at rates over 50-60 breaths per minute (most common physical sign)
  • Tachycardia
  • Fever, usually in the range of 38.5-39°C
  • Mild conjunctivitis or pharyngitis
  • Diffuse expiratory wheezing
  • Nasal flaring
  • Intercostal retractions
  • Cyanosis
  • Inspiratory crackles
  • Otitis media
  • Apnea, especially in infants younger than 6 weeks
  • Palpable liver and spleen from hyperinflation of the lungs and consequent depression of the diaphragm

Causes

RSV is the most common pathogen (85%), but other organisms occasionally produce a similar clinical picture.

  • Adenovirus (11%) occasionally causes a similar syndrome with a more virulent course.
  • Epidemics of bronchiolitis due to parainfluenza virus usually begin earlier in the year and tend to occur every other year.
  • Other less common etiologic agents include the following:
  • Ear, nose, or mouth inoculation
    • Exposure to an adult with a URI
    • Daycare exposure (significant)
    • Idiopathic

More on Pediatrics, Bronchiolitis

Overview: Pediatrics, Bronchiolitis
Differential Diagnoses & Workup: Pediatrics, Bronchiolitis
Treatment & Medication: Pediatrics, Bronchiolitis
Follow-up: Pediatrics, Bronchiolitis
References
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References

  1. [Guideline] American Academy of Pediatrics Subcommittee on Diagnosis and Management of Bronchiolitis. Diagnosis and management of bronchiolitis. Pediatrics. Oct 2006;118(4):1774-93. [Medline]. [Full Text].

  2. Schuh S, Lalani A, Allen U, Manson D, Babyn P, Stephens D. Evaluation of the utility of radiography in acute bronchiolitis. J Pediatr. Apr 2007;150(4):429-33. [Medline].

  3. [Best Evidence] Plint AC, Johnson DW, Patel H, Wiebe N, Correll R, Brant R, et al. Epinephrine and dexamethasone in children with bronchiolitis. N Engl J Med. May 14 2009;360(20):2079-89. [Medline].

  4. American Academy of Pediatrics. Reassessment of the indications for ribavirin therapy in respiratory syncytial virus infections. American Academy of Pediatrics Committee on Infectious Diseases. Pediatrics. Jan 1996;97(1):137-40. [Medline].

  5. American Academy of Pediatrics. Respiratory syncytial virus immune globulin intravenous: indications for use. American Academy of Pediatrics Committee on Infectious Diseases, Committee on Fetus and Newborn. Pediatrics. Apr 1997;99(4):645-50. [Medline].

  6. 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].

  7. Centers for Disease Control and Prevention (CDC). Respiratory syncytial virus activity--United States, 1999-2000 season. MMWR Morb Mortal Wkly Rep. Dec 8 2000;49(48):1091-3. [Medline].

  8. Cheney J, Barber S, Altamirano L, Medico Cirujano, Cheney M, Williams C. A clinical pathway for bronchiolitis is effective in reducing readmission rates. J Pediatr. Nov 2005;147(5):622-6. [Medline].

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  23. van Woensel JB, Kimpen JL, Sprikkelman AB, et al. Long-term effects of prednisolone in the acute phase of bronchiolitis caused by respiratory syncytial virus. Pediatr Pulmonol. Aug 2000;30(2):92-6. [Medline].

  24. Wang EE, Law BJ, Stephens D. Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) prospective study of risk factors and outcomes in patients hospitalized with respiratory syncytial viral lower respiratory tract infection. J Pediatr. Feb 1995;126(2):212-9. [Medline].

  25. Weber MW, Mulholland EK, Greenwood BM. Respiratory syncytial virus infection in tropical and developing countries. Trop Med Int Health. Apr 1998;3(4):268-80. [Medline].

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Further Reading

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Keywords

upper respiratory tract infection, URI, respiratory syncytial virus, RSV, rhinorrhea, tachypnea, bronchiolitis, asthma, lower respiratory tract infection, infection of the small airways, viral infection of the small airways, bronchioles, adenovirus, parainfluenza virus, Mycoplasma pneumoniae, M pneumoniae, rhinovirus, enterovirus, influenza virus, Chlamydia pneumoniae, C pneumoniae, infection of bronchiolar respiratory cells, infection of ciliated epithelial cells, peribronchiolar lymphocytic infiltrate

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Contributor Information and Disclosures

Author

Mark Louden, MD, FACEP, Assistant Medical Director, Emergency Department, Duke Raleigh Hospital
Mark Louden, MD, FACEP is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians
Disclosure: Nothing to disclose.

Medical Editor

Kirsten A Bechtel, MD, Associate Professor, Department of Pediatrics, Yale University School of Medicine; Attending Physician, Department of Pediatric Emergency Medicine, Yale-New Haven Children's Hospital
Kirsten A Bechtel, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Wayne Wolfram, MD, MPH, Clinical Associate Professor, Departments of Pediatrics, Children's Hospital and University of Cincinnati
Wayne Wolfram, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Pediatrics, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Richard G Bachur, MD, Associate Professor of Pediatrics, Harvard Medical School; Associate Chief and Fellowship Director, Attending Physician, Division of Emergency Medicine, Children's Hospital of Boston
Richard G Bachur, MD is a member of the following medical societies: American Academy of Pediatrics, Society for Academic Emergency Medicine, and Society for Pediatric Research
Disclosure: Nothing to disclose.

 
 
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