Which ventilator measurement reflects alveolar distention during testing?

• A. Pplat
• B. PIP
• C. PEEP
• D. Raw

Answer: (A)

Alveolar distention is best assessed by the pressure in the lungs when there is no airflow, which is measured during an inspiratory hold. This plateau pressure reflects the distending pressure across the alveolar walls and lung parenchyma, independent of airway resistance. It’s the value clinicians use to gauge how much of the ventilator pressure is actually distending the alveoli.

Peak inspiratory pressure includes the pressure needed to overcome airway resistance in addition to the distending pressure, so it overestimates distention when resistance is high. Positive end-expiratory pressure sets a baseline pressure at end expiration and doesn’t measure distention during the inspiratory phase. Airway resistance (often summarized as Raw) is a measure of how hard air is pushing through the airways, not the distension of the alveoli themselves.

So, the measurement that reflects alveolar distention during testing is the plateau pressure; keeping it at safe levels helps minimize volutrauma.