Accession Number:

ADA297022

Title:

Cardiopulmonary Responses to Pressure Breathing.

Descriptive Note:

Final rept. Apr 93-Sep 94,

Corporate Author:

DUKE UNIV MEDICAL CENTER DURHAM NC F G HALL LAB FOR ENVIRONMENTAL RESEARCH

Report Date:

1995-05-01

Pagination or Media Count:

81.0

Abstract:

Positive pressure breathing PPB is used to maintain the alveolar partial pressure of oxygen during altitude exposures in excess of 12,000 meters 36,000 feet. At altitudes up to 33,000 feet the alveolar gas tensions may be kept within the normal range by increasing the concentration of oxygen in the inspired gas mixture. Above this altitude, however, alveolar oxygen tensions fall below normal levels despite breathing 100 oxygen Sharp Ernsting, 1988. Furthermore, during high-acceleration high-G maneuvers, even at lower altitudes, there is a tendency for microatelectasis formation and development of intrapulmonary right-to-left shunt, which may be accentuated during 100 oxygen breathing Wagner, et al. 1977. Raising the pressure inside the breathing circuit throughout the breathing cycle PPB is well established as a method of maintaining alveolar oxygen tension at high altitudes Gagge, et al. 1945 and under high G- forces. Burns and Baildin 1988 studied the rates of arterial desaturation during acceleration with positive pressure breathing at 50 mmHg and 70 mmHg. They found that the rate of oxygen desaturation was less with PPB than without PPB suggesting a possible improvement in VAIQ relationships, at least in lowV aQ regions or shunt. This is equivalent to continuous positive airway pressure CPAP used clinically to augment arterial oxygenation in patients.

Subject Categories:

  • Stress Physiology
  • Anatomy and Physiology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE