Journal of Applied Physiology, Vol 58, Issue 2 339-345, Copyright © 1985 by American Physiological Society
Pleural stress pressure as a force to control liquid accumulation and maintain lung expansion
K. Harada, T. Mutsuda, N. Saoyama, N. Hamaguchi and Y. Shimada
Total gas pressure in the pleural space is more subatmospheric than that in
the alveolar cavity. This pressure difference minus elastic recoil pressure
of the lung was termed stress pressure. We investigated the relationship
between stress pressure and a force that would hold the lung against the
chest wall to prevent accumulation of liquid. The condition was a pleural
space with an enlarged pleural surface pressure. Dogs anesthetized with
pentobarbital sodium were placed in a box maintained subatmospherically at
approximately -30 cmH2O and breathed atmospheric air for 4 h. Liquid volume
in the pleural space of the dogs was measured under conditions of
thoracotomy. In the normal group, the volume of the pleural liquid was
within the normal range of approximately 2.0 ml and the visceral and the
parietal pleura made contact. In the pneumothorax group, established by
injecting 50 ml of air into the pleural space, the liquid increased
significantly in all cases by a mean value of approximately 12 ml. Thus
pleural stress pressure seems to be an important force holding the lung
against the chest wall and aiding in the control of accumulation of liquid
in a more subatmospheric pleural space.
