Elevation gradient of intrathoracic pressure.

Abstract

Intrathoracic (intrapleural) pressure was measured in 15 anesthetized mongrel dogs held in the vertical position. A small balloon attached to a polyethylene catheter was inserted, without admission of air, into the chest through the 3rd intercostal space, or above the first rib, and passed down to the costophrenic sulcus. Along the lateral, anterolateral, and posterolateral aspects of the lung surface a vertical gradient of pressure was found, amounting to an increase of +0.21 cm H2O/cm descent, which was absent when the animal was in the horizontal position. This pressure gradient agrees closely with the gradient predicted on the basis of the mean density of lung tissue at end expiration in these animals. Among the implications of these findings is the possible existence of regional differences in the elastic work of breathing, based on differences in vertical distance between parts of the lung. Submitted on May 2, 1960