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G-Protection Mechanisms Afforded by the Anti-G Suit Abdominal Bladder With and Without Pressure Breathing.
- Source :
- Aviation, Space & Environmental Medicine; Oct2011, Vol. 82 Issue 10, p972-977, 6p
- Publication Year :
- 2011
-
Abstract
- Background: G protection afforded by the abdominal bladder of a pneumatic anti-G suit is usually attributed to counteraction of G-induced caudad displacement of the heart and pooling of blood in the abdominal veins. The study examined whether the abdominal bladder might provide G protection also via other mechanisms. Methods: Each subject was exposed to +Gz loads while sitting relaxed, wearing a full-coverage anti-G suit modified to permit separate pressurization of the abdominal and leg bladders. In two experimental series (N = 8, N = 14), subjects were breathing at positive airway pressure (PPB); in a third series, five subjects were breathing at atmospheric airway pressure. Intrathoracic pressures were estimated by use of esophageal catheters. Results: During PPB at high G loads, intrathoracic pressure was higher with than without the pressurized abdominal bladder. In 7 of the 14 subjects, basilar intrathoracic pressure exceeded airway pressure during PPB when the abdominal bladder was pressurized. The mean arterial pressure response at high G loads was higher in this subset of subjects (55 ± 23 mmHg) than in the subjects in whom airway pressure exceeded intrathoracic pressure (41 ± 27 mmHg). Without PPB at increased G load, the intrathoracic pressure gradient was higher with than without the pressurized abdominal bladder. Discussion: During PPB, the abdominal bladder acts as an airway counterpressure, thereby facilitating pressure transmission from the airways to the thorax and hence improving G protection. It also appears that in several individuals, pressure may be transmitted from the abdominal bladder to the thorax and heart. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00956562
- Volume :
- 82
- Issue :
- 10
- Database :
- Supplemental Index
- Journal :
- Aviation, Space & Environmental Medicine
- Publication Type :
- Periodical
- Accession number :
- 67429129
- Full Text :
- https://doi.org/10.3357/ASEM.3058.2011