Clinical meaning
Mechanical ventilation provides respiratory support by delivering positive pressure breaths through an endotracheal tube or tracheostomy when patients cannot maintain adequate oxygenation or ventilation independently. Common modes include assist-control (AC), which delivers a set number of breaths at a set tidal volume with patient-triggered additional breaths; synchronized intermittent mandatory ventilation (SIMV), which delivers set breaths while allowing spontaneous breathing between; and pressure support ventilation (PSV), which augments patient-initiated breaths. Key settings include FiO2 (fraction of inspired oxygen, 21-100%), tidal volume (6-8 mL/kg ideal body weight), respiratory rate, and PEEP (positive end-expiratory pressure that prevents alveolar collapse). Complications include ventilator-associated pneumonia (VAP), barotrauma, auto-PEEP, and ventilator-associated events. The VAP prevention bundle includes head of bed elevation, oral care with chlorhexidine, daily sedation vacation, and daily readiness-to-wean assessment.
Exam relevance
Risk factors: - Prolonged intubation duration increasing VAP risk - Supine positioning allowing aspiration of oropharyngeal secretions - Poor oral hygiene providing bacterial reservoir for aspiration - Over-sedation preventing spontaneous breathing trials - High ventilator pressures causing barotrauma