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ventilator-associated-pneumonia-pathogenesis-and-clinical-findings

Ventilator-Associated Pneumonia: Pathogenesis and Clinical Findings Respiratory failure or inability Risk factors: e.g. immunocompromised, poor swallowing to maintain airway ability, weakened respiratory muscles, chronic disease Insertion of endotracheal tube (ETT) for invasive mechanical ventilation to maintain respiration Paralytics and sedatives lead to inhibition of cough reflex Damage to cilia on epithelial cells of trachea during insertion of ETT ↓ Mucociliary clearance Insertion of nasogastric (NG) tube for feeding Constant opening by NG tube ↓ esophageal sphincter function Introduction of oropharyngeal microbes during intubation Severe acute illness impairs phagocytosis and dysregulates T- cells (mechanism unclear) Medications, chronic disease, or severe acute illness can weaken immune system Desensitization of pharyngoglottal adduction reflex (PAR) (PAR normally induces closure of epiglottis to protect the airway when swallowing) ↑ Reflux of gastric contents Accumulation of subglottic secretions containing microbes Microbial colonization on inside of ETT Development of biofilm on inside of ETT Dislodgement of biofilm into lower airway ↑ Age or chronic disease can weaken respiratory function Micro aspirations of subglottic and gastric contents Impaired mechanisms to remove microbes from airway Positive pressure pushes microbes down Fever/rigors ↑ White blood cell count Introduction of pathogenic microbes to airway Susceptible patient (not required for infection) Septic shock See Distributive Shock slide Sepsis Microbes descend airway and infect lungs Ventilator-Associated Pneumonia (VAP) Occurs > 48-72 hours after intubation ↑ Inflammatory response at infection site promoting immune cell extravasation and cytokine release Cytokine signalling ↑ permeability of capillaries leading to ↑ fluid leakage into interstitium and alveoli Authors: Sravya Kakumanu Reviewers: Ben Campbell *Tara Lohmann *Bryan Yipp * MD at time of publication Acute respiratory distress syndrome See ARDS pathogenesis slide Pleural effusion Lung consolidation on chest x-ray (CXR) ↑ Sputum production to clear fluid on CXR (Note: In patients with Acute Respiratory Distress Syndrome (ARDS), look for VAP consolidation in non- within alveoli/airways (may be Positive microbial culture from sputum dependent/upper regions of the lung where ARDS consolidation would be unexpected to extend to) purulent in worse infections) Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published September 2, 2022 on www.thecalgaryguide.com