Mechanical ventilation - PEEP effect on FRC and oxygenation
Core concept
- PEEP = pressure maintained in the airway at end-expiration
- Holds alveoli above their closing volume -> inc FRC
- Prevents end-expiratory derecruitment and cyclic opening/closing (atelectrauma)
- Recruited alveoli -> dec shunt fraction, improved V/Q matching -> inc PaO2
- PEEP is the oxygenation knob; minute ventilation is the CO2 knob
- Oxygenation = FiO2 + PEEP (mean airway pressure)
- CO2 = tidal volume x respiratory rate
- PEEP does not treat every hypoxaemia - it works on recruitable, collapsed lung
- Excellent: ARDS, atelectasis, cardiogenic pulmonary oedema
- Useless or harmful: intracardiac right-to-left shunt, pulmonary AVM, unilateral consolidation, emphysema
3 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access