BRONCHIOLITIS Year 4 Paediatrics Notes OmpathStudy

BRONCHIOLITIS Year 4 · Paediatrics Collection: 4TH YEAR ALL NOTES / PAEDS / PAEDS 4.1 / Agisa -- Slide 1 BRONCHIOLITIS DR. AGISA KEGODE CONSULTANT PAEDIATRICIAN AND PULMONOLOGIST Slide 2 INTRODUCTION Bronchiolitis is an acute inflammatory injury of bronchioles.\nMostly caused by viruses. Bronchiolitis usually affects children younger than 2 years, with a peak in infants aged 3-6 months.\nAcute bronchiolitis is the most common cause of lower respiratory tract infection in the first year of life. Slide 3 ANATOMY Slide 4 PATHOPHYSIOLOGY Bronchioles are small airways (< 2 mm in diameter) and lack cartilage and submucosal glands.\nThe terminal bronchiole, a 16th-generation airway, is the final conducting airway that terminates in the respiratory bronchioles.\nThe acinus (ie, the gas exchange unit of the lung) consists of respiratory bronchioles, the alveolar duct, and alveoli.\nThe bronchiolar lining consists of surfactant-secreting Clara cells and neuroendocrine cells, which are the source of bioactive products such as somatostatin, endothelin, and serotonin Slide 5 PATHOPHYSIOLOGY Complex immunologic mechanisms play a role in the pathogenesis of bronchiolitis.\nType 1 allergic reactions mediated by immunoglobulin E (IgE) may account for some clinically significant bronchiolitis. Infants who are breastfed with colostrum rich in immunoglobulin A (IgA) appear to be relatively protected from bronchiolitis. Necrosis of the respiratory epithelium is one of the earliest lesions in bronchiolitis and occurs within 24 hours of acquisition of infection. Proliferation of goblet cells results in excessive mucus production, whereas epithelial regeneration with nonciliated cells impairs elimination of secretions.\nLymphocytic infiltration may result in submucosal edema Cytokines and chemokines, released by infected respiratory epithelial cells, amplify the immune response by increasing cellular recruitment into infected airways. Interferon and interleukin (IL)–4, IL-8, and IL-9 are found in high concentrations in respiratory secretions of infected patients. Slide 6 PATHOPHYSIOLOGY Bronchiolar injury and the consequent interplay between inflammatory and mesenchymal cells can lead to diverse pathologic and clinical syndromes.\nThe effects of bronchiolar injury may begin 18 to 24 hours after the infection and 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 Slide 7 The inflammation, edema, and debris result in obstruction of bronchioles, leading to hyperinflation, increased airway resistance, atelectasis, and ventilation-perfusion mismatching.\nBronchoconstriction has not been described. Infants are affected most often because of their small airways, high closing volumes, and insufficient collateral ventilation. Recovery begins with regeneration of bronchiolar epithelium after 3-4 days; however, cilia do not appear for as long as 2 weeks.\nMucus plugs are instead predominantly removed by macrophages. Slide 8 In tropical/subtropical climates, the season may be more prolonged and seems to correlate with the rainy season. Attack rates within families are as high as 45% and are higher in childcare centers. Rates of hospital-acquired infection can range from 20-47%. Virtually all children experience RSV infection within the first 3 years of life, but a previous infection does not convey complete immunity.\nReinfection is common; however, significant antibody titers from prior infection ameliorate the severity of symptoms. Slide 9 AETIOLOGY Most cases of bronchiolitis result from a viral pathogen, such as RSV, rhinovirus, human metapneumovirus (hMPV), parainfluenza virus, adenovirus, coronavirus, influenza virus or human bocavirus. In one third of hospitalized cases of bronchiolitis, two or more viruses may be detected, especially when using molecular-based testing.\nBronchiolitis is highly contagious. The virus that causes it is spread from person to person through direct contact with nasal secretions, airborne droplets, and fomites. Slide 10 Common organisms RSV is the most commonly isolated agent in 75% of children younger than 2 years who are hospitalized for bronchiolitis. Rhinoviruses, the cause of the common cold, may cause bronchiolitis or lower respiratory tract infection and are frequently detected in dual infections. Rhinovirus may lead to a shorter hospitalization than RSV-associated bronchiolitis. Parainfluenza virus causes 10-30% of all bronchiolitis cases. Parainfluenza type 3 is more likely to cause bronchiolitis than types 1, 2 or 4 which are associated with croup Adenovirus accounts for 5-10% of bronchiolitis cases while influenza virus accounts for 10-20%. Mycoplasma Pneumonia accounts for 5-15%, particularly among older children and adults. Human metapneumovirus, has been increasingly implicated as an etiologic agent in