Accession Number:

ADA297414

Title:

The Ventriculo-Arterial Coupling Ratio During Transient Gz Events.

Descriptive Note:

Journal article,

Corporate Author:

NORTH DAKOTA STATE UNIV FARGO

Report Date:

1995-07-01

Pagination or Media Count:

7.0

Abstract:

It has been shown by Westerhof et al. that the ratio TIT where pi RpSAC and Rp is total peripheral resistance, SAC is systemic arterial compliance, and T is heart period is approximately a constant in all mammals under resting conditions such that diastolic pressure is sufficiently high to assure adequate coronary perfusion. The aim of this study is to determine if the ratio TIT is constant under the transient condition of a rapid onset rate Gz acceleration. We hypothesize that the ratio is held constant by the cardiovascular control system. Four male baboons were subjected to 10 second rapid onset Gz profiles and aortic pressure and flow were recorded. Rp and C were calculated using a 2-element windkessel model and T was determined by the inverse of heart rate. All parameters were calculated on a beat-to-beat basis. It was found that the ratio increased very little at 2 Gz and increased dramatically at 3 and 5 Gz, disproving our hypothesis. This increase was due to large increases in peripheral resistance and changes in heart rate over the course of a Gz run. The increases are presumed to represent baroreceptor reflex response to the drop in aortic pressure experienced during Gz stress. The ratio TIT returned to its initial resting value shortly after the Gz stressor was removed.

Subject Categories:

  • Anatomy and Physiology
  • Medicine and Medical Research
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE