The scalars depicted here are flow, volume, airway pressure, and esophageal pressure. They were obtained from a patient receiving pressure-controlled ventilation. What problem is depicted by these ventilator graphics?

A. inverse I:E ratio ventilation
B. alveolar overdistention
C. decreased lung compliance
D. trigger dyssynchrony

ANS: D
A. Incorrect response: See explanation D.
B. Incorrect response: See explanation D.
C. Incorrect response: See explanation D.
D. Correct response: Focus primarily on the two pressure-time scalars.

Note that on the esophageal pressure-time (bottom-most) scalar, the arrows indicate an esophageal pressure change. The arrow on the left represents the beginning of patient inspiratory effort. Under normal circumstances, when no auto-PEEP is present, a drop in airway pressure would be taking place concurrently with the initial decrease in esophageal pressure, and an assisted breath would be triggered. However, the presence of auto-PEEP requires the patient to generate an inspiratory effort in excess of the auto-PEEP to trigger inspiration. In this situation, the esophageal pressure changed 25 cm H2O as 0.7 seconds elapsed before the airway pressure changed to trigger a breath. This level of pressure is a significant triggering workload on the patient. ?