High PEEP increases physiologic dead space by which mechanism?

High PEEP increases physiologic dead space by which mechanism?

• A. Increases Physiologic Dead Space
• B. Decreases Tidal Volume
• C. Has No Effect On Dead Space
• D. Decreases Oxygenation

Answer: (A)

High PEEP raises alveolar pressures; when pushed too high, some alveoli become overdistended rather than simply recruited. Overdistension compresses the surrounding pulmonary capillaries, reducing blood flow to those ventilated units. Ventilated but poorly perfused alveoli become alveolar dead space, so the physiologic dead space increases. Moderate PEEP can recruit collapsed units and reduce dead space, but excessive PEEP shifts the balance toward increased dead space due to capillary compression and reduced perfusion of ventilated areas.

High PEEP raises alveolar pressures; when pushed too high, some alveoli become overdistended rather than simply recruited. Overdistension compresses the surrounding pulmonary capillaries, reducing blood flow to those ventilated units. Ventilated but poorly perfused alveoli become alveolar dead space, so the physiologic dead space increases. Moderate PEEP can recruit collapsed units and reduce dead space, but excessive PEEP shifts the balance toward increased dead space due to capillary compression and reduced perfusion of ventilated areas.