Which of the following terms refers to the difference between the inspiratory compliance and expiratory compliance?

Question

A. resistance
B. hysteresis
C. elastance?D. volume dependency

Answer 1

ANS: B
A. Incorrect response: Resistance is the impedance to flow in a conducting system. It is the ratio of the change in pressure (gradient) divided by the flow. When no pressure gradient exists, no flow is present, and resistance in the system is zero.
B. Correct response: Plotting an inspiratory compliance curve against an expiratory compliance yields a graphic that displays hysteresis. The two curves are not identical. If they were identical, the two curves would overlap. However, they do not because more pressure is required to initially inflate alveoli at the beginning of inspiration and to stabilize the surfactant layer than is needed to derecruit alveoli during lung deflation (expiration). Consequently, less pressure is required to deflate the lungs than is needed to inflate them.
C. Incorrect response: Elastance is the reciprocal of compliance.
D. Incorrect response: Respiratory system compliance is nonlinear and volume dependent. Because different pressures are required to inflate the lungs at various points throughout inspiration, one compliance measurement is meaningless. The volume at which the lung compliance was measured is necessary to make that measurement meaningful.