Mechanical Vent Test 4 Practice

When reading a pressure-volume loop during a system check, the loop should close back at zero volume at the end of expiration. If the loop starts at zero on the volume axis but does not return to zero during expiration, it means some of the tidal volume is being lost in the circuit rather than returning to the patient side. A leak in the ventilator circuit allows gas to escape before it can be accounted for on expiration, so the expiratory portion of the loop never returns to the baseline. This explains the persistent offset on the volume axis.

Lung overdistention would typically alter pressure patterns and the shape of the loop rather than leave a persistent baseline offset. Trigger sensitivity mainly affects the timing of breaths and patient effort, not the closed-path volume return. Disconnection would cause abrupt changes or loss of the loop's continuity rather than a gradual failure to return to zero volume on expiration.