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Related Experiment Videos

Systolic time intervals during +Gz acceleration

T B Graboys, E D Michaelson

    Journal of Applied Physiology
    |July 1, 1976
    PubMed
    Summary
    This summary is machine-generated.

    Systolic time intervals (STI) noninvasively measured cardiovascular responses to Gz acceleration. Findings show STI can estimate changes in heart rate, ejection time, and cardiac output during simulated high-G exposure.

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    Area of Science:

    • Cardiovascular Physiology
    • Aerospace Medicine
    • Biomedical Engineering

    Background:

    • High Gz acceleration significantly impacts cardiovascular function.
    • Noninvasive monitoring of cardiovascular responses during Gz exposure is crucial for safety and performance.
    • Systolic time intervals (STI) offer a potential noninvasive method to assess cardiac function.

    Purpose of the Study:

    • To investigate the feasibility of using STI to noninvasively estimate transient cardiovascular function changes during +Gz acceleration.
    • To analyze the effects of varying +Gz levels on STI parameters.
    • To assess the recovery patterns of cardiovascular function after Gz exposure.

    Main Methods:

    • Systolic time intervals (STI) were recorded in 8 healthy male volunteers.

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  • Measurements were taken before, during, and after 30-second exposures to +3 Gz, +5 Gz, and +7 Gz.
  • Cardiovascular variables including heart rate (HR), left ventricular ejection time (LVETc), and pre-ejection period (PEPc) were analyzed.
  • Estimated stroke volume (SV) and cardiac output (CO) were derived from STI.

    • Main Results:

    • Heart rate (HR) and all measured STI parameters increased proportionally with increasing +Gz levels.
    • Changes in STI, including PEPc and PEP/LVET, persisted into the early recovery period at higher Gz levels.
    • HR and STI returned to baseline levels within 60 seconds of recovery.
    • Estimated cardiac output (CO) generally increased as stroke volume (SV) decreased during acceleration.
    • CO remained slightly below baseline during recovery due to persistently low estimated SV.

    Conclusions:

    • Systolic time intervals (STI) provide a feasible noninvasive method for assessing cardiovascular adjustments during +Gz acceleration.
    • STI can track transient changes in cardiac function, including HR, LVETc, and PEPc, under simulated high-G conditions.
    • The study validates the use of STI for monitoring cardiovascular responses in aerospace and related fields.