"Bunt bradycardia": two cases of slowing of heart rate inflight during negative Gz.
Two cases are presented of Canadian Forces pilots who experienced inflight bradycardia during 15 s of -1 Gz acceleration. The bradycardia was characterized by rapid cardio-deceleration, stable bradycardia, then cardio-acceleration during recovery following the -Gz exposure that was slower than the cardio-deceleration. Vagally mediated bradycardia in humans subjected to -Gz acceleration stress has been previously documented in laboratory studies. This bradycardia may be operationally significant since it signifies the presence of other physiological effects that predispose aviators to reduced subsequent +Gz tolerance. Research to investigate the implications of reduced +Gz tolerance following -Gz acceleration is warranted.
Banks
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RD
Naval Aerospace and Operational Medical Institute, NAS Pensacola, FL.
Gray
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G
D000337:Aerospace Medicine; D006112:Gravitation; D006339:Heart Rate / Q000502:physiology*; D006801:Humans