G-protection mechanisms afforded by the anti-G suit abdominal bladder with and without pressure breathing.
2011 (English)In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, Vol. 82, no 10, 972-7 p.Article in journal (Refereed) Published
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.
Place, publisher, year, edition, pages
2011. Vol. 82, no 10, 972-7 p.
anti-G suit, G load, G tolerance, transdiaphragmal pressure, transpulmonary pressure
IdentifiersURN: urn:nbn:se:kth:diva-44489DOI: 10.3357/ASEM.3058.2011ISI: 000295187000007PubMedID: 21961402ScopusID: 2-s2.0-80054787870OAI: oai:DiVA.org:kth-44489DiVA: diva2:450728
QC 201110212011-10-212011-10-212011-10-21Bibliographically approved