Heart Rate and Blood Pressure Responses to +Gz Following Varied-Duration - Gz

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Authors
  1. Goodman, L.S.
  2. Banks, R.D.
  3. Grissett, J.D.
  4. Saunders, P.L.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
The push-pull effect has been defined previously as decreased +Gz tolerance caused by previous baseline zero or -Gz exposure. Earlier work indicates that the delay in BP (PB) recovery during +Gz is a function of time at -Gz, and is due to the lengthened time-course of sympathetically mediated peripheral vasoconstriction. The purpose of this study was to retrospectively determine whether heart rate (HR) varies with BP as duration at preceding -Gz increased. Continuous ECG R-R interval data from 15 s of +2.25Gz after preceding 2, 5, 10 or 15 s at -2Gz obtained from previous experiments were analyzed and compared with the previously reported BP data. Repeated measures ANOVA and regression analyses were used to compare +2.25Gz HR responses after the four -Gz conditions and one control +2.25Gz condition. An initial rapid rise in HR was observed for all conditions with a consistent steady-state plateau achieved after the first 7 s of +2.25Gz. However, there were significant differences in mean HR attained during the +2.25Gz plateau for preceding 15 s -2.0 Gz vs. the control, 2, 5, and 10s -Gz conditions (109 + or - 1.1 vs. 102 + or -1.8, 100 + or - 2.0, 97 + or - 1.1 and 101 + or - 1.1, bpm, respectively; p<0.05). HR, unlike BP, increases briskly across all preceding -Gz time conditions, adapting within the initial baroreflex-compensatory time frame typically expected for +Gz exposures. TRUNCATED
Keywords
Push-pull effect;Positive acceleration;Negative acceleration;Cardiovascular regulation;Cartoid-cardiac baroflex
Report Number
DCIEM-98-P-35 — Reprint
Date of publication
22 Mar 1998
Number of Pages
8
Reprinted from
Aviation, Space, and Environmental Medicine, Vol 71, No 2, 2000, p 137-141
DSTKIM No
CA001306
CANDIS No
513088
Format(s):
Hardcopy;Document Image stored on Optical Disk

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