The best assessment of the function of the diaphragm during inspiration is obtained by measuring which of the following?

a. Airway resistance
b. Pressure-time product
c. Pressure-volume curve
d. Maximum inspiratory pressure

ANS: B
The pressure-time product is a way of estimating the contributions of the diaphragm during in-spiration. It is probably a better indication of a patient's effort to breathe than measurement of work derived from pressure-volume curves. Airway resistance is a measure of how much opposi-tion there is to gas movement through the airways. An increase in airway resistance will cause the diaphragm to work harder. However, airway resistance is not a direct way of assessing the func-tion of the diaphragm. Maximum inspiratory pressure provides nonspecific information about the function of the respiratory muscles in general, not specifically the diaphragm.