Respiratory Syncytial Virus (RSV) (see Respiratory Syncytial Virus, [[Respiratory Syncytial Virus]]): most cases with a defined viral etiology are due to RSV (RSV accounts for 45-90% of bronchiolitis cases in infants/young children)
Nitrogen Dioxide Inhalation (see Nitrogen Dioxide, [[Nitrogen Dioxide]])
Nitrous Fumes (see Nitrous Fumes, [[Nitrous Fumes]]): found in silo gas, jet and missile fuels, metal pickling fumes, fires
Ozone Inhalation (see Ozone, [[Ozone]]) (low solubility in water): delayed injury to lower airways (bronchioles/alveoli)
Sulfur Dioxide Inhalation (see Sulfur Dioxide, [[Sulfur Dioxide]])
Phosgene Gas Inhalation (see Phosgene Gas, [[Phosgene Gas]])
Other
Inflammatory Bowel Disease (see Inflammatory Bowel Disease, [[Inflammatory Bowel Disease]]): small case series have reported association with inflammatory bowel disease
Idiopathic Bronchiolitis: no clear history of exposure or infection
Physiology
Infectious Bronchiolitis
Acute Inflammatory Disorder of Small Airways: peribronchiolar inflammation with epithelial cell necrosis
Air Trapping/Hyperinflation
Atelectasis
Toxic Fume Bronchiolitis
Determinants of Potential for Damage
Particle Size
Particles >10 µm will impact in upper airway
Particles <5 µm will impact in the lower airways and alveoli
pH: acid burns coagulate underlying tissue but alkali (ammonia, etc.) liquefact and penetrate mucosa
Chemical Reactivity
Water Solubility
Diagnosis
Arterial Blood Gas (ABG)
Hypoxemia: may persist for weeks after recovery
CBC: absence of leukocytosis (and normal differential)
CXR/Chest CT Patterns
Hyperinflation with Air Trapping
Flattened Diaphragms
Peribrobchial Thickening
Focal Atelectasis
Pneumonia
Nodular Shadows: may be seen in some cases of infectious bronchiolitis
Pulmonary Function Tests (PFT’s): small airways (<2 mm) pattern
FEF25-75: decreased
Increased airway resistance and peripheral airway obstruction (and hypoxemia) may be seen years later in children who have experienced repeated episodes of RSV bronchiolitis
Bronchoscopy : usually not specifically helpful but may reveal organisms in infectious cases
Lung Biopsy: may be necessary in chronic progressive cases
Clinical Presentations
Infectious Bronchiolitis
General Comments
Risk of Hospitalization and Severe Bronchiolitis: high in infants with congenital heart disease, immunodeficiency, prematurity, or chronic lung disease
Risk of Severe Bronchiolitis: high in infants with family history of asthma and second-hand smoke exposure
Prodrome: several days of upper respiratory tract symptoms
Meta-Analysis of Bronchodilator Use in Bronchiolitis (2014) [MEDLINE]: bronchodilators (albuterol, salbutamol) do not improve hypoxemia, decrease rate of hospital admission after outpatient treatment, decrease the duration of hospitalization, or decrease the time to resolution of illness at home
However, study was limited by small sample sizes, lack of standardized study design, and lack of validated outcomes across the studies
Nebulized Racemic Epinephrine (see Epinephrine, [[Epinephrine]])
Immunocompromised Adults with Stem Cell Transplant: aerosolized ribavirin decreases mortality rate in RSV pneumonia in this population [MEDLINE] [MEDLINE]
Immunocompromised Adults with Stem Cell Transplant: oral and intravenous ribavirin have been shown to be efficacious in small trials [MEDLINE] [MEDLINE]
Immunocompromised Adults with Lung/Solid Organ Transplant: the efficacy of ribavirin in these patients is unknown [MEDLINE] [MEDLINE]
Palivizumab (Synagis) (see Palivizumab, [[Palivizumab]]): RSV-specific humanized monoclonal antibody
No clinical benefit in the therapy of RSV infection
Licensed for the prevention of serious RSV lower respiratory tract disease in children at high risk of RSV infection (prematurity, bronchopulmonary dysplasia, congenital heart disease)
Combination Ribavirin + Intravenous Immunoglobulin (IVIG) (see Ribavirin, [[Ribavirin]] and Intravenous Immunoglobulin, [[Intravenous Immunoglobulin]])
May be indicated in severely ill patients with RSV
Combination Palivizumab (Synagis) + Intravenous Immunoglobulin (IVIG) (see Palivizumab, [[Palivizumab]] and Intravenous Immunoglobulin, [[Intravenous Immunoglobulin]]): has not been studied
RSV-Specific Immunoglobulin (RSVIG)
No longer available
Combination Ribavirin + Corticosteroids (see Ribavirin, [[Ribavirin]] and Corticosteroids, [[Corticosteroids]])
Has been used in small series of lung transplant patients with RSV [MEDLINE]
Toxic Fume Exposure
Supportive care
Prognosis
Mild Cases: resolve within several days
Mortality Rates
Previously Healthy Infants: 0.5-1.5%
Infants with Immunodeficiency/Cancer Chemotherapy/Pulmonary or Heart Disease/Pulmonary Hypertension: 15-40%
References
Respiratory syncytial virus pneumonia in a lung transplant recipient: case report. J Heart Lung Transplant. 1992;11(1 Pt 1):77 [MEDLINE]
Combination therapy with aerosolized ribavirin and intravenous immunoglobulin for respiratory syncytial virus disease in adult bone marrow transplant recipients. Bone Marrow Transplant. 1995;16(3):393 [MEDLINE]
Immunotherapy of respiratory syncytial virus pneumonia following bone marrow transplantation. Bone Marrow Transplant. 1996;17(6):1051 [MEDLINE]
Respiratory syncytial virus-associated infections in adult recipients of solid organ transplants. J Heart Lung Transplant. 1998;17(2):202 [MEDLINE]
Respiratory syncytial virus infection in adult BMT recipients: effective therapy with short duration nebulised ribavirin. Bone Marrow Transplant. 1998;21(4):423 [MEDLINE]
Respiratory syncytial virus upper respiratory tract illnesses in adult blood and marrow transplant recipients: combination therapy with aerosolized ribavirin and intravenous immunoglobulin. Bone Marrow Transplant. 2000;25(7):751 [MEDLINE]
Respiratory syncytial virus immune globulin treatment of lower respiratory tract infection in pediatric patients undergoing bone marrow transplantation – a compassionate use experience. Bone Marrow Transplant. 2000;25(2):161 [MEDLINE]
Respiratory syncytial virus infection of the lower respiratory tract: radiological findings in 108 children. Eur Radiol. 2001;11(12):2581-4. Epub 2001 May 3 [MEDLINE]
Safety and pharmacokinetics of palivizumab therapy in children hospitalized with respiratory syncytial virus infection. Pediatr Infect Dis J. 2004;23(8):707 [MEDLINE]
Treatment of respiratory syncytial virus pneumonia in a lung transplant recipient: case report and review of the literature. Pharmacotherapy. 2004;24(7):932 [MEDLINE]
Pharmacologic treatment of bronchiolitis in infants and children: a systematic review. Arch Pediatr Adolesc Med. 2004;158(2):127 [MEDLINE]
Intravenous ribavirin is a safe and cost-effective treatment for respiratory syncytial virus infection after lung transplantation. J Heart Lung Transplant. 2005;24(12):2114 [MEDLINE]
Wheezing Rhinovirus Illnesses in Early Life Predict Asthma Development in High-Risk Children. Am J Respir Crit Care Med. 2008 October 1; 178(7): 667–672 [MEDLINE]
Epinephrine for bronchiolitis. Cochrane Database Syst Rev. 2011 [MEDLINE]
Steroids and bronchodilators for acute bronchiolitis in the first two years of life: systematic review and meta-analysis. BMJ. 2011;342:d1714 [MEDLINE]
Racemic adrenaline and inhalation strategies in acute bronchiolitis. N Engl J Med. 2013 Jun;368(24):2286-93 [MEDLINE]
Respiratory viral infections among children with community-acquired pneumonia and pleural effusion. Scand J Infect Dis. 2013 Jun;45(6):478-83. doi: 10.3109/00365548.2012.754106. Epub 2013 Jan 3 [MEDLINE]
Respiratory syncytial virus lower respiratory disease in hematopoietic cell transplant recipients: viral RNA detection in blood, antiviral treatment, and clinical outcomes. Clin Infect Dis. 2013 Dec;57(12):1731-41. Epub 2013 Oct 8 [MEDLINE]
Oral ribavirin for treatment of respiratory syncitial virus and parainfluenza 3 virus infections post allogeneic haematopoietic stem cell transplantation. Bone Marrow Transplant. 2013;48(12):1558 [MEDLINE]
Successful systemic high-dose ribavirin treatment of respiratory syncytial virus-induced infections occurring pre-engraftment in allogeneic hematopoietic stem cell transplant recipients. Transpl Infect Dis. 2013 Aug;15(4):435-40. Epub 2013 May 20 [MEDLINE]
Bronchodilators for bronchiolitis. Cochrane Database Syst Rev. 2014;6:CD001266 [MEDLINE]
Association between Respiratory Syncytial Virus Activity and Pneumococcal Disease in Infants: A Time Series Analysis of US Hospitalization Data. PLoS Med. 2015 Jan 6;12(1):e1001776. doi: 10.1371/journal.pmed.1001776. eCollection 2015 [MEDLINE]
