SEARCH RESULTS FOR: Bronchiolitis-updated

Bronchiolitis-updated

Bronchiolitis: Pathogenesis and clinical findings Viral pathogen, most commonly respiratory syncytial virus (RSV) - but can be others such as rhinovirus, adenovirus, parainfluenza, influenza, and coronaviruses - initially colonizes the nasopharyngeal mucosa Virus travels via the epithelium to the lower airways to the terminal bronchioles (small airways) Authors: Nick Baldwin Rebecca Lindsay Reviewers: Kayla Nelson, Yan Yu Timothy Fu, Danielle Nelson* *MD at time of publication Upper airway mucosal inflammation Bronchiolitis (bronchiole inflammation) Apnea (cessation of breathing; via unknown mechanism, potentially apnea reflex) RSV-fusion protein facilitates fusion of the virus to the host cell and directs viral penetration as well as facilitates fusion of the infected cell with its healthy neighbors Forms syncytia (multinucleated cells) Cytokines are released into circulation ↑ thermo- regulatory set- point at the hypothalamus Mild Fever Copious coryza (nasal discharge) Protein and fluid leak into nasopharyngeal interstitium ↑ Capillary permeability Protein and fluid leak into the bronchiole interstitium, accumulating around airway walls Airway wall becomes thickened, more readily apparent on x-ray Peribronchial cuffing (X-ray finding: bronchi appear like thickened ‘cuffs’ when viewed head-on) Inflammation stimulates the upregulation of mucous secreting goblet cells ↑ mucous production Mucous within alveoli ↑ intra- alveolar surface tensionà collapsing alveolar walls During inspiration, air enters the collapsed alveoli if airway is not yet occluded ↑ intra-alveolar pressure causes the alveoli to suddenly pop open Inspiratory crackles on auscultation Syncytia slough off the bronchial epithelium into airways Airways become narrower and occlude Disruption of the ciliated epithelial cells (which transport mucous out of the airways and into the pharynx, to be swallowed or evacuated) ↓ mucous clearance from airways Excess airway mucous triggers cough reflex Cough Interstitial edema Nasal Congestion Air is absorbed distal to occlusion (gas trapping) When all air is absorbed, alveoli collapse (resorptive atelectasis) ↓ gas exchange between blood and air in remaining alveoli ↓ O2 saturation & ↑ CO2 content of blood Narrower airways, especially during expiration, causes audible turbulent airflow Wheeze on auscultation Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Re-Published November 29, 2020 on www.thecalgaryguide.com