PEEP
Summary
PEEP (Positive End-Expiratory Pressure) is a ventilator setting that maintains positive airway pressure at the end of expiration to prevent alveolar collapse. It improves oxygenation by increasing functional residual capacity and reducing ventilation-perfusion mismatch. PEEP is crucial in managing ARDS and other conditions with poor lung compliance.
Detail
PEEP works by keeping alveoli open during expiration, preventing their collapse and subsequent cyclic opening/closing that can cause ventilator-induced lung injury. Physiologically, PEEP increases functional residual capacity (FRC), improves ventilation-perfusion matching, and enhances oxygen diffusion across the alveolar-capillary membrane. The optimal PEEP level balances improved oxygenation against potential cardiovascular compromise - excessive PEEP can reduce venous return and cardiac output by increasing intrathoracic pressure. In ARDS, PEEP helps recruit collapsed alveoli and is typically set between 5-20 cmH2O based on FiO2 requirements and compliance. Auto-PEEP (intrinsic PEEP) can occur in obstructive diseases like COPD when expiration is incomplete, leading to air trapping. Contraindications include untreated pneumothorax and severe cardiovascular instability. PEEP is monitored via pressure-volume loops and arterial blood gases.
Sources
- Harrison's Principles of Internal Medicine
- Marino's The ICU Book
- ARDS Network Protocol
- Principles of Critical Care (Hall, Schmidt, Wood)
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