EXSUFFLATION WITH NEGATIVE PRESSURE

Abstract

OF THE various physical methods developed for eliminating bronchial secretions,* exsufflation with negative pressure (E. W. N. P.) was recently reported as the most effective.† The principle of E. W. N. P. depends on (1) gradual inflation of the lungs by a positive pressure of 30 to 40 mm. Hg; (2) a swift withdrawal of air from the fully expanded lungs at the beginning of expiration, utilizing a sudden pressure drop to 30 to 40 mm. Hg below the atmosphere; (3) explosive decompression produced by a 60 to 80 mm. Hg decrease in pressure in 0.02 seconds. The latter pressure drop would result in an instantaneous intrathoracic gas expansion of approximately 10% of the total lung capacity, or 400 to 500 cc. of air, if the suction blower provided an air velocity of this magnitude. E. W. N. P., therefore, includes effects of the two methods of mechanically eliminating bronchial