Bronchiolitis overview: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
Bronchiolitis is transmitted by air droplets. It is caused by [[Human respiratory syncytial virus|RSV]] which leads to [[infection]] of the [[nasopharyngeal]] [[mucosa]]. After the [[infection]], the [[virus]] will spread to the [[Lower respiratory tract|lower airway tracts]] till it reaches the [[bronchioles]] where the [[viral replication]] takes place. The viral [[infection]] induces [[inflammation]] which leads to [[edema]] and [[necrosis]] of the [[bronchioles|bronchiolar]] [[epithelium]]. [[Cough reflex]] occurs due to exposure of the subepithelial [[tissue]] and [[nerve fibers]]. [[Vascular]] permeability increases leading to [[edema]] and [[swelling]]. Histopathologically, [[bronchiolitis obliterans]] shows [[intraluminal]] [[polyps]], [[inflammatory]] [[Infiltration (medical)|infiltration]], and [[macrophages]]. Constrictive bronchiolitis shows thickening of the [[airways]] and inter luminal narrowing. | |||
==Causes== | ==Causes== | ||
Bronchiolitis usually affects children under the age of 2, with a peak age of 3 - 6 months. Bronchiolitis is a common disease in the children and sometimes severe [[illness]]. [[respiratory syncytial virus|Respiratory syncytial virus (RSV)]] is the most common cause of bronchiolitis. Other [[viruses]] that can cause [[bronchiolitis]] include [[adenovirus]], [[influenza]], and [[parainfluenza]]. It may be caused by [[bacterial]] [[organisms]] like [[Legionella pneumophila|Legionella pneumophilia]] and [[mycoplasma pneumonia]]. Other non[[infectious]] causes include [[smoking]], [[collagen vascular disease]], and post [[bone marrow transplant]]. | |||
==Differentiating Bronchiolitis from Other Diseases== | ==Differentiating Bronchiolitis from Other Diseases== | ||
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==Epidemiology and Demographics== | ==Epidemiology and Demographics== | ||
Bronchiolitis is one of the most common acute [[Respiratory disease|respiratory diseases]] that affect the [[infants]] and [[children]]. Bronchiolitis affects around 3000 per 100,000 children in the United States. It occurs during fall, winter and early spring. It can affect any age group but mostly affects [[infants]] especially those under 2 years. [[Bronchiolitis]] ratio in boys is more than girls and it is more common among the native Americans, Alaskans and Hispanics. [[Bronchiolitis]] has low [[mortality rate]] despite the high number of hospitalizations. | |||
==Risk Factors== | ==Risk Factors== | ||
Bronchiolitis has a different range of [[risk factors]] and it can be differentiated based on the age. In the adult, common risk factors in the development of bronchiolitis include exposure to [[cigarette]] smoke, living in crowded areas and [[immunocompromised]] patients. In [[infants]], the [[risk factors]] include age < 6 months, lack of [[breast-feeding|breastfeeding]], [[prematurity]], and young children with [[congenital heart diseases]]. | |||
==Natural History, Complications, and Prognosis== | ==Natural History, Complications, and Prognosis== | ||
If left untreated, in the first 2-3 days the patient with | If left untreated, in the first 2-3 days the patient with bronchiolitis presents with [[Upper respiratory tract infection|mild upper respiratory symptoms]], [[Shortness of breath]], [[wheezing]], persistent prominent [[cough]], [[tachypnea]]. [[Chest wall]] [[retraction]] and [[nasal]] flaring usually develop between the third and seventh day. Symptoms gradually disappear within the next 2 weeks. Complications are usually observed among patients younger than 2 months of age, premature infants, and patients with other medical conditions ([[congenital heart disease]], [[Chronic obstructive pulmonary disease|chronic pulmonary disease]], and [[immunodeficiencies]]). Severity scores can be used to estimate the prognosis. | ||
==Diagnosis== | ==Diagnosis== | ||
===History and Symptoms=== | ===History and Symptoms=== | ||
Bronchiolitis occurs mainly in the [[infants]]. The patients usually give a history of [[nasal congestion]] and [[phlegm]] [[discharge]]. Its classical presentation is [[fever]], [[cough]], and [[dyspnea]]. The [[virus]] is transmitted from person to person by direct contact with [[nasal]] [[fluids]] or by [[Airborne transmission|airborne droplets]]. Although [[Human respiratory syncytial virus|RSV]] generally causes only mild symptoms in an adult, it can cause severe [[illness]] in an infant. [[Bronchiolitis]] is seasonal and appears more often in the fall and winter months. It is a very common reason for infants to be hospitalized during winter and early spring. It is estimated that by their first year, more than half of all [[infants]] have been exposed to [[RSV]]. | |||
===Physical Examination=== | ===Physical Examination=== | ||
Patients infected with | Patients infected with bronchiolitis have a [[Toxicity|toxic]] appearance and may be [[cyanotic]]. [[Fever]] is one of the signs of the [[disease]] but the lack of it does not exclude the diagnosis. [[Lung]] examination shows abnormalities in [[Inspection (medicine)|inspection]] and [[auscultation]]. On inspection, [[intercostal]] and [[Substernal pain|substernal retractions]] can be observed. On [[auscultation]], [[wheezing]] and [[crackles]] can be clearly heard with a decrease in the [[respiratory sounds]]. Extrapulmonary manifestations can occur as well like [[pharyngitis]], [[conjunctivitis]], [[arrythmias|arrhythmias]], [[tachycardia]], and [[seizures]]. | ||
===Laboratory Findings=== | ===Laboratory Findings=== | ||
Bronchiolitis diagnosis depends mainly on the [[symptoms]] and [[physical examination]] as the laboratory diagnosis is not specific for the [[disease]]. The lab tests include [[Viral pathogenesis|viral pathogen tests]] which are commonly used like [[Enzyme linked immunosorbent assay (ELISA)|ELISA]], [[Immunofluorescence|immunofluorescent]] assays, and optical [[immunoassays]]. [[Complete blood count]] also is not specific for [[bronchiolitis]]. [[Pulmonary function tests]] may be helpful in supporting the diagnosis and excluding other [[Chronic obstructive pulmonary disease|obstructive lung diseases]]. | |||
===X ray=== | ===X ray=== | ||
Chest x-ray in cases of | Chest x-ray in cases of bronchiolitis is usually nonspecific and may be inefficient for differentiating bronchiolitis from other [[Lower respiratory tract infection|lower respiratory tract infections]]. A chest x-ray may show [[atelectasis]] and [[Consolidation (medicine)|consolidations]]. It is used also in excluding other medical conditions like [[pneumonia]]. | ||
===CT=== | ===CT=== | ||
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==Treatment== | ==Treatment== | ||
===Medical Therapy=== | ===Medical Therapy=== | ||
The predominant therapy for bronchiolitis is providing supportive measures. Supportive therapy includes frequent small feeds and [[oxygen therapy]]. In severe cases, infants may require [[intravenous fluids]] and feed via a [[Nasogastric tube|nasogastric tube]]. In extreme cases, [[mechanical ventilation]] or the use of [[continuous positive airway pressure]] ([[CPAP]]) might be necessary. Prophylaxis is indicated in infants with [[hemodynamically]] significant [[heart disease]] and preterm infants who require >21% [[oxygen]] for at least the first 28 days of life. The drug of choice for prophylaxis is [[Palivizumab]]. | |||
===Surgery=== | ===Surgery=== | ||
Surgical intervention is not recommended for the management of | Surgical intervention is not recommended for the management of bronchiolitis. | ||
===Primary Prevention=== | ===Primary Prevention=== | ||
Effective measures for the primary prevention of bronchiolitis include hand washes, contact avoidance with patients with symptomatic [[respiratory infections]], and prevention of [[tobacco]] smoke exposure. These preventive measures are to prevent the viral dissemination during the [[RSV]] season. In patients with high risk of developing severe [[infections]], [[Immunization#Pasive and active immunization|passive immunization]] with [[Palivizumab|palivizumab]] is recommended. | |||
===Secondary Prevention=== | ===Secondary Prevention=== | ||
There | There are no secondary preventive measures available for bronchiolitis. | ||
==References== | ==References== | ||
Revision as of 14:41, 31 July 2017
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]
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Overview
Bronchiolitis is the most common lower respiratory tract infection in pediatric patients between 1 month and 2 years of age. It is usually caused by the respiratory syncytial virus (RSV) and is characterized by inflammation, edema, and necrosis of the bronchiole's epithelium. It is classified according to the histological features into bronchiolitis obliterans, proliferative bronchiolitis, diffuse panbronchiolitis, and respiratory bronchiolitis. Bronchiolitis severity score is used to classify bronchiolitis into 4 classes. Typical clinical manifestations include rhinitis, cough, wheezing, respiratory rales (crackles), use of respiratory accessory muscles and/or nasal flaring. In the adult, common risk factors in the development of bronchiolitis include exposure to cigarette smoke and living in crowded areas and immunocompromised patients. In infants, the risk factors include age < 6 months, lack of breastfeeding, prematurity, and young children with congenital heart diseases. The mainstay of treatment of bronchiolitis is supportive therapy.
Historical Perspective
Bronchiolitis disease was first reported in 1899 when it was discovered by members of University of Minnesota. The disease was fully described in 1901 by Dr. Lange.
Classification
Bronchiolitis is classified based on the age and the different forms of the disease. Bronchiolitis should be classified in order to understand how it may occur and the clinical manifestation that could be observed. According to age, bronchiolitis is classified into either adults or infants. Based on the different histological features, it can be classified into acute infectious bronchiolitis, bronchiolitis obliterans, proliferative bronchiolitis, diffuse panbronchiolitis and respiratory bronchiolitis. Based on the Bronchiolitis Severity Score (BSS), bronchiolitis is classified into 4 classes.
Pathophysiology
Bronchiolitis is transmitted by air droplets. It is caused by RSV which leads to infection of the nasopharyngeal mucosa. After the infection, the virus will spread to the lower airway tracts till it reaches the bronchioles where the viral replication takes place. The viral infection induces inflammation which leads to edema and necrosis of the bronchiolar epithelium. Cough reflex occurs due to exposure of the subepithelial tissue and nerve fibers. Vascular permeability increases leading to edema and swelling. Histopathologically, bronchiolitis obliterans shows intraluminal polyps, inflammatory infiltration, and macrophages. Constrictive bronchiolitis shows thickening of the airways and inter luminal narrowing.
Causes
Bronchiolitis usually affects children under the age of 2, with a peak age of 3 - 6 months. Bronchiolitis is a common disease in the children and sometimes severe illness. Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis. Other viruses that can cause bronchiolitis include adenovirus, influenza, and parainfluenza. It may be caused by bacterial organisms like Legionella pneumophilia and mycoplasma pneumonia. Other noninfectious causes include smoking, collagen vascular disease, and post bone marrow transplant.
Differentiating Bronchiolitis from Other Diseases
Bronchiolitis must be differentiated from other respiratory and cardiac diseases that present with similar clinical manifestations. Based on cough and dyspnea, bronchiolitis is differentiated from asthma, COPD, pneumonia, congestive heart failure, diffuse idiopathic neuroendocrine cell hyperplasia, tuberculosis, pertussis, foreign body aspiration, pulmonary embolism, and Harman-Rich syndrome.
Epidemiology and Demographics
Bronchiolitis is one of the most common acute respiratory diseases that affect the infants and children. Bronchiolitis affects around 3000 per 100,000 children in the United States. It occurs during fall, winter and early spring. It can affect any age group but mostly affects infants especially those under 2 years. Bronchiolitis ratio in boys is more than girls and it is more common among the native Americans, Alaskans and Hispanics. Bronchiolitis has low mortality rate despite the high number of hospitalizations.
Risk Factors
Bronchiolitis has a different range of risk factors and it can be differentiated based on the age. In the adult, common risk factors in the development of bronchiolitis include exposure to cigarette smoke, living in crowded areas and immunocompromised patients. In infants, the risk factors include age < 6 months, lack of breastfeeding, prematurity, and young children with congenital heart diseases.
Natural History, Complications, and Prognosis
If left untreated, in the first 2-3 days the patient with bronchiolitis presents with mild upper respiratory symptoms, Shortness of breath, wheezing, persistent prominent cough, tachypnea. Chest wall retraction and nasal flaring usually develop between the third and seventh day. Symptoms gradually disappear within the next 2 weeks. Complications are usually observed among patients younger than 2 months of age, premature infants, and patients with other medical conditions (congenital heart disease, chronic pulmonary disease, and immunodeficiencies). Severity scores can be used to estimate the prognosis.
Diagnosis
History and Symptoms
Bronchiolitis occurs mainly in the infants. The patients usually give a history of nasal congestion and phlegm discharge. Its classical presentation is fever, cough, and dyspnea. The virus is transmitted from person to person by direct contact with nasal fluids or by airborne droplets. Although RSV generally causes only mild symptoms in an adult, it can cause severe illness in an infant. Bronchiolitis is seasonal and appears more often in the fall and winter months. It is a very common reason for infants to be hospitalized during winter and early spring. It is estimated that by their first year, more than half of all infants have been exposed to RSV.
Physical Examination
Patients infected with bronchiolitis have a toxic appearance and may be cyanotic. Fever is one of the signs of the disease but the lack of it does not exclude the diagnosis. Lung examination shows abnormalities in inspection and auscultation. On inspection, intercostal and substernal retractions can be observed. On auscultation, wheezing and crackles can be clearly heard with a decrease in the respiratory sounds. Extrapulmonary manifestations can occur as well like pharyngitis, conjunctivitis, arrhythmias, tachycardia, and seizures.
Laboratory Findings
Bronchiolitis diagnosis depends mainly on the symptoms and physical examination as the laboratory diagnosis is not specific for the disease. The lab tests include viral pathogen tests which are commonly used like ELISA, immunofluorescent assays, and optical immunoassays. Complete blood count also is not specific for bronchiolitis. Pulmonary function tests may be helpful in supporting the diagnosis and excluding other obstructive lung diseases.
X ray
Chest x-ray in cases of bronchiolitis is usually nonspecific and may be inefficient for differentiating bronchiolitis from other lower respiratory tract infections. A chest x-ray may show atelectasis and consolidations. It is used also in excluding other medical conditions like pneumonia.
CT
CT scan shows nonspecific findings in the cases of bronchiolitis that can be found in other diseases. These findings are e centrilobular nodules, bronchiolar wall thickening, ground glass appearance and parenchymal cysts.
MRI
There are no MRI findings associated with bronchiolitis.
Other Imaging Findings
There are no additional imaging findings for bronchiolitis.
Other Diagnostic Studies
There are no additional diagnostic findings for bronchiolitis.
Treatment
Medical Therapy
The predominant therapy for bronchiolitis is providing supportive measures. Supportive therapy includes frequent small feeds and oxygen therapy. In severe cases, infants may require intravenous fluids and feed via a nasogastric tube. In extreme cases, mechanical ventilation or the use of continuous positive airway pressure (CPAP) might be necessary. Prophylaxis is indicated in infants with hemodynamically significant heart disease and preterm infants who require >21% oxygen for at least the first 28 days of life. The drug of choice for prophylaxis is Palivizumab.
Surgery
Surgical intervention is not recommended for the management of bronchiolitis.
Primary Prevention
Effective measures for the primary prevention of bronchiolitis include hand washes, contact avoidance with patients with symptomatic respiratory infections, and prevention of tobacco smoke exposure. These preventive measures are to prevent the viral dissemination during the RSV season. In patients with high risk of developing severe infections, passive immunization with palivizumab is recommended.
Secondary Prevention
There are no secondary preventive measures available for bronchiolitis.