July 1, 2016Open Access

Effect of postural changes on cardiovascular parameters across gender

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Healthy subjects (n=28). Intervention: Postural changes and lower body negative pressure vs. Supine rest. Primary outcome: Cardiovascular parameters across gender.

Key Result

Postural changes and lower body negative pressure significantly altered cardiovascular parameters, but there were no significant differences between healthy young males and females in blood pressure regulation, myocardial contractility, or sympathetic nerve activity.

Study Design

Type

Observational (n=28)

Multicenter

Structured PICO

Do postural changes and lower body negative pressure affect cardiovascular parameters differently across gender in healthy subjects?

Population

28 healthy subjects (16 male, 12 female)

Intervention

3 interventions: head-down tilt (HDT), HDT with lower body negative pressure (HDT+ LBNP at −30 mm Hg), and head-up tilt (HUT), each for 10 minutes separated by a 10 minutes recovery period

Comparator

Rest (supine)

Outcome

Cardiovascular parameters including heart rate, heart rate variability metrics, systolic blood pressure, mean arterial pressure, diastolic blood pressure, total peripheral resistance index, stroke index, cardiac index, index of contractility, left ventricular work index, and left ventricular ejection timesurrogate

In healthy subjects, cardiovascular responses to postural changes and lower body negative pressure do not differ by gender, and lower body negative pressure partially mimics the cardiovascular responses of head-up tilt.

Limitations

Females were not controlled to a specific phase of their menstrual cycle.
None of the females were identified as taking oral contraceptives, adding uncertainty to their hormonal profile.
Small sample size limits the generalizability of the study.
Differences in protocol duration (10 minutes) compared to other studies that used longer periods of central hypovolemia.

Abstract

Introduction: We investigated the effect of postural changes on various cardiovascular parameters across gender. Twenty-eight healthy subjects (16 male, 12 female) were observed at rest (supine) and subjected to 3 interventions; head-down tilt (HDT), HDT with lower body negative pressure (HDT+ LBNP at −30 mm Hg), and head-up tilt (HUT), each for 10 minutes separated by a 10 minutes recovery period. Methods: Measurements were recorded for heart rate (HR), standard deviation of the normal-to-normal intervals, root mean square of successive differences between the normal-to-normal intervals, heart rate variability-low frequency (LFRRI), heart rate variability-high frequency (HFRRI), low frequency/high frequency ratio (LFRRI/HFRRI), systolic blood pressure (SBP), mean arterial pressure (MAP), diastolic blood pressure (DBP), total peripheral resistance index (TPRI), stroke index (SI), cardiac index (CI), index of contractility (IC), left ventricular work index, and left ventricular ejection time. Results: Across all cardiovascular parameters, there was a significant main effect of the intervention applied but there was no significant main effect of gender across all parameters. Conclusions: The results suggest that there are no specific gender differences in regards to the measured variables under the conditions of this study. Furthermore, these results suggest that in healthy subjects, there appears to be evidence that LBNP partially elicits similar cardiovascular responses to HUT, which supports the use of LBNP as an intervention to counteract the effects of central hypovolemia.

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