Long-duration +Gz acceleration on cardiac volumes determined by two-dimensional echocardiography.
To enhance protection of humans exposed to long-duration low-gravity environments such as the Space Shuttle and National Aerospace Plane during re-entry or in the short-duration high(-)+Gz environment of fighter aircraft, the effects of +Gz acceleration on cardiovascular hemodynamics must be understood. This study reports the use of two-dimensional echocardiography in normal men during +Gz acceleration. The heart's position in relation to the chest did not change during acceleration up to +7 Gz. The success in maintaining high-quality images during exposures to G-forces of this magnitude may be attributed to the relatively low rate of G onset. End-diastolic volumes (EDV) and stroke volumes (SV) decreased during a +Gz acceleration ramp that increased until the subject experienced peripheral light loss (PLL) (P < .05). An inflated G-suit partially counteracted this effect. By 30 seconds of a +3 Gz acceleration plateau, the protective effects of the inflated G-suit to maintain EDV is lost and the EDV of the inflated G-suit was lower than the EDV of the uninflated G-suit (P < .05).
Tripp
L D
LD
Systems Research Laboratories Inc., Dayton, Ohio.
Jennings
T J
TJ
Seaworth
J F
JF
Howell
L L
LL
Goodyear
C
C
D000054:Acceleration; D000328:Adult; D002498:Centrifugation; D015150:Echocardiography, Doppler; D006112:Gravitation; D005676:Gravity Suits; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D013026:Space Flight; D013318:Stroke Volume / Q000502:physiology*; D013997:Time Factors