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

Personal Author(s) : Stolp, Bryant W. ; Arles, Stephen P. ; Dear, Guy L. ; Chimlak, James M. ; Gleaton, Charles H.

PDF Url : ADA297022

Report Date : MAY 1995

Pagination or Media Count : 81

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 a/Q regions or shunt. This is equivalent to continuous positive airway pressure (CPAP) used clinically to augment arterial oxygenation in patients.

Descriptors :   *OXYGEN, *LUNG, *CARDIOVASCULAR SYSTEM, *HEART, *PRESSURE BREATHING, ACCELERATION, RATES, CYCLES, GASES, MIXTURES, SATURATION, RESPONSE, TENSION, HIGH ALTITUDE, CIRCUITS, RESPIRATION, HIGH ACCELERATION, LOW ALTITUDE, ARTERIES, ALVEOLI, PARTIAL PRESSURE.

Subject Categories : Stress Physiology
      Anatomy and Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE