Cardiorespiratory and Performance Responses to Sustained Pressure Breathing.

Abstract

Positive pressure breathing (PPB) is used to provide pilot life support during cockpit depressurization at altitudes at which the ambient pressure is insufficiently high to maintain adequate oxygen tension even when breathing 100% 02. Although pulmonary barotrauma and hypotension can usually be prevented by an external chest counterpressure jerking and a G-suit, involuntary hyperpnea, presumably caused by activation of an upper airway stretch receptor, can limit pilot performance, This phenomenon was investigated in 10 normal volunteers wearing the COMBAT EDGE, who were instrumented to obtain arterial blood samples while different forms of applying positive pressure breathing were applied. In order to study effects on cardiac output, four subjects were instrumented with pulmonary artery catheters while they breathed 34% O2_at a simulated altitude of 24,900 ft in a hypobaric chamber, in order to simulate 100% 02 breathing at 50,000 feet. Psychomotor performance was assessed using a subset of the Tri-Service Cognitive Battery implemented on a laptop computer.