Calculate the intrapleural pressure if atmospheric pressure is 765 millimeters of mercury, assuming that the subject is at rest (not inhaling or exhaling).

A. 4 millimeters of mercury

B. 0 millimeters of mercury

C. 761 millimeters of mercury

D. 765 millimeters of mercury

C. 761 millimeters of mercury

Explanation:

Because it is at rest, the intrapulmonary pressure must be equal to the atmospheric pressure. And the intrapleural pressure is usually 4 millimeters of mercury (mmHg) less than the intrapulmonary pressure. So we have the following

intrapulmonary pressure = 765 millimeters of mercury

intrapleural pressure = intrapulmonary pressure - 4 millimeters of mercury

Then:

intrapleural pressure = (765 - 4) millimeters of mercury

intrapleural pressure = 761 millimeters of mercury