EFFECT OF EXTENDING G-SUIT COVERAGE ON CARDIOVASCULAR-RESPONSES TO POSITIVE PRESSURE BREATHING

The purpose of this study was to compare cardiovascular responses of s ubjects exposed to long-duration positive pressure breathing (PPB) whi le wearing a standard (Combat Edge; CE) vs. extended coverage (Tactica l Life Support System; TLSS) G-suit. Twelve experienced subjects, wear ing TLSS and CE, were separately exposed to counterbalanced 60, 70, 80 , and 88 mm Hg PPB for up to 10 min continuously. Termination resulted if presyncopal symptoms arose. G-suit inflation was 4 x mask/jerkin p ressure. Using TLSS all subjects completed 10 min of PPB at all levels , vs. 7 and 5 subjects completing 10 min at 80 and 88 mm Hg, respectiv ely, using the CE ensemble (p < 0.001). Heart rate was significantly e levated at all PPB levels using CE (p < 0.0001) vs. TLSS. Stroke and C ardiac Indexes were significantly lower with CE at all levels vs. TLSS (p < 0.0001), and mean arterial blood pressure failed to be maintaine d at the 80 and 88 PPB mm Hg levels using CE (p < 0.0001). Extended G- suits afford superior protection against PPB-induced cardiovascular dy sfunction vs. standard ensembles and consequently permit use of higher levels of PPB. This is due to the larger and more uniform application of pressure in the leg G-suit bladders, augmenting venous return and stroke volume.