The following two graphic loops show which of the following conditions?

a. Leak in the patient-ventilator circuit
b. Increased airway resistance
c. Decreased lung compliance
d. Active exhalation

ANS: A
Because the expiratory volume does not return to zero in these graphics, a leak is present in the patient-ventilator circuit. Increased airway resistance would show as a scooped-out expiratory flow on the flow-volume loop, which may not end before the next breath. Decreased lung com-pliance would show as a "duck bill" on the pressure-volume loop. Active exhalation would make the volume tracing drop below zero.