Pressure-controlled ventilation (PCV) differs from volume-controlled ventilation (VCV) in that PCV delivers a fixed pressure with which resulting gas flow pattern?

• A Constant (square wave) inspiratory flow throughout inspiration
• B Sinusoidal flow mimicking spontaneous breathing
• C Accelerating flow at end of inspiration to ensure complete tidal volume delivery
• D Decelerating (descending ramp) inspiratory flow as alveolar pressure rises toward set pressure limit ✓

Explanation

In PCV, the ventilator delivers gas at a constant set inspiratory pressure. Initially there is a large pressure gradient between ventilator and alveoli, producing high peak flow. As alveolar pressure rises to match the set pressure, the driving gradient decreases, and flow decelerates in a ramp pattern. This decelerating flow pattern improves gas distribution to lung units with different time constants compared to the square-wave flow of VCV, potentially improving oxygenation and reducing peak airway pressures in ARDS and obstructed airways.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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