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Heart rate and blood pressure responses to +Gz following varied-duration -Gz.
Aviat Space Environ Med. 2000 Feb; 71(2):137-41.AS

Abstract

BACKGROUND

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 (BP) recovery during +Gz is a function of time at -G7, and is due to the lengthened time-course of sympathetically mediated peripheral vasoconstriction.

HYPOTHESIS

The purpose of this study was to retrospectively determine whether heart rate (HR) varies with BP as duration at preceding -Gz increased.

METHODS

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.

RESULTS

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+/-1.1 vs. 102+/-1.8, 100+/-2.0, 97+/-1.1 and 101+/-1.1, bpm, respectively; p<0.05).

CONCLUSIONS

HR, unlike BP, increases briskly across all preceding -Gz time conditions, adapting within the initial baroreflex-compensatory time frame typically expected for +Gz exposures. These results suggest there may be a threshold effect for HR response. Consequently, vasoconstrictor response is a critical adaptive mechanism during +Gz when preceded by long (>10 s) -Gz exposures.

Authors+Show Affiliations

Goodman LS
Defence and Civil Institute of Environmental Medicine, Aerospace Life Support Section, Toronto, Ontario, Canada. len.goodman@dciem.dnd.ca
Banks RD
No affiliation info available
Grissett JD
No affiliation info available
Saunders PL
No affiliation info available

MeSH

Adaptation, PhysiologicalAerospace MedicineAnalysis of VarianceBlood PressureBradycardiaElectrocardiographyHeart RateHomeostasisHumansHypergravityHypogravityMonitoring, PhysiologicRegression AnalysisRetrospective StudiesTime FactorsVasoconstriction

Pub Type(s)

Journal Article

Language

eng

PubMed ID

10685587

Citation

Goodman, L S., et al. "Heart Rate and Blood Pressure Responses to +Gz Following Varied-duration -Gz." Aviation, Space, and Environmental Medicine, vol. 71, no. 2, 2000, pp. 137-41.
Goodman LS, Banks RD, Grissett JD, et al. Heart rate and blood pressure responses to +Gz following varied-duration -Gz. Aviat Space Environ Med. 2000;71(2):137-41.
Goodman, L. S., Banks, R. D., Grissett, J. D., & Saunders, P. L. (2000). Heart rate and blood pressure responses to +Gz following varied-duration -Gz. Aviation, Space, and Environmental Medicine, 71(2), 137-41.
Goodman LS, et al. Heart Rate and Blood Pressure Responses to +Gz Following Varied-duration -Gz. Aviat Space Environ Med. 2000;71(2):137-41. PubMed PMID: 10685587.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Heart rate and blood pressure responses to +Gz following varied-duration -Gz. AU - Goodman,L S, AU - Banks,R D, AU - Grissett,J D, AU - Saunders,P L, PY - 2000/2/24/pubmed PY - 2000/3/4/medline PY - 2000/2/24/entrez SP - 137 EP - 41 JF - Aviation, space, and environmental medicine JO - Aviat Space Environ Med VL - 71 IS - 2 N2 - BACKGROUND: 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 (BP) recovery during +Gz is a function of time at -G7, and is due to the lengthened time-course of sympathetically mediated peripheral vasoconstriction. HYPOTHESIS: The purpose of this study was to retrospectively determine whether heart rate (HR) varies with BP as duration at preceding -Gz increased. METHODS: 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. RESULTS: 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+/-1.1 vs. 102+/-1.8, 100+/-2.0, 97+/-1.1 and 101+/-1.1, bpm, respectively; p<0.05). CONCLUSIONS: HR, unlike BP, increases briskly across all preceding -Gz time conditions, adapting within the initial baroreflex-compensatory time frame typically expected for +Gz exposures. These results suggest there may be a threshold effect for HR response. Consequently, vasoconstrictor response is a critical adaptive mechanism during +Gz when preceded by long (>10 s) -Gz exposures. SN - 0095-6562 UR - https://www.unboundmedicine.com/medline/citation/10685587/Heart_rate_and_blood_pressure_responses_to_+Gz_following_varied_duration__Gz_ DB - PRIME DP - Unbound Medicine ER -