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adult-pneumonia-pathogenesis-and-clinical-findings

Adult Pneumonia: Pathogenesis and clinical findings Author: Laura Byford-Richardson Reviewers: Tara Shannon, *Yan Yu, Sadie Kutz , Natalie Morgunov, *Kerri Johannson, *Julie Carson *MD at time of publication Smoking à suppressed neutrophil function and damaged lung epithelium Chronic lung conditions e.g. COPD, asthma, lung canceràdestroys lung tissue and offers pathogen more niduses for infection Immune suppression e.g. HIV, sepsis, glucocorticoids, chemotherapyà suppression of immune response Systemic inflammatory response towards invading microbe Systemic cytokine release leads to a disruption in hypothalamic thermoregulation Exposure to a pathogen via inhalation, aspiration, contiguous Notes: or hematological mechanism Susceptible host and/or virulent pathogen Proliferation of microbe in lower airways and alveoli Local response by alveolar epithelial cells release chemokines into surrounding tissue to recruit neutrophils to the site of inflammation • Pathogens can be bacteria, viruses, fungi and parasites • Pneumonia is a lower respiratory tract infection (in contrast to upper respiratory tract infections such as bronchitis) and can be further classified by location of exposure: community, health- care, hospital acquired Inflammatory response varies depending on type of invading pathogen (i.e. S. Pneumonia causes a lobar pattern and Influenza A & B cause an interstitial pattern) LOBAR: Accumulation of neutrophils and plasma exudate from capillaries into alveoli specific to a lung area/lobe INTERSTITIAL: Accumulation of infiltrates (i.e. inflamed cellular debris) in the alveolar walls (i.e. space between the alveolar spaces and bloodstream) Fever Notes: • Other signs and symptoms of pneumonia exist such as chest pain, accessory muscle use, crackles on auscultation and fatigue • These signs and symptoms are less specific to the ones outlined on this slide Irritation and attempted clearance of airways Fluid infiltrates are inside alveoli, airway clearance leads to phlegm production Productive Cough Fluid build up does not allow X-rays to pass through à white opacity on plain film at site of fluid buildup Consolidation on CXR Alveolar sacs blocked by fluid accumulation Thickening of alveolar walls ↑ diffusion distance between alveoli & capillaries Irritated alveolar walls trigger cough reflex Since fluid infiltrates are NOT in the alveoli, attempts to empty the alveoli through coughing doesn’t lead to production of fluid Dry Cough Chills/Rigors ↓ Exchange of CO2 and O2 Hypoxemia Triggers peripheral and central chemoreceptors to ↑ respiratory drive Dyspnea Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published Sept 26 2016, updated Feb 9, 2022 on www.thecalgaryguide.com