Pulse contour methods to estimate cardiovascular indices in micro- and hypergravity.

Area of Science:

• Cardiovascular physiology
• Space medicine
• Biomedical engineering

Background:

• Noninvasive health monitoring is crucial for long-duration space missions.
• Assessing cardiovascular indices like cardiac output (CO) and total peripheral resistance (TPR) is vital.
• Previous methods for CO and TPR estimation lacked evaluation in diverse gravitational conditions.

Purpose of the Study:

• To compare the performance of 10 different methods for estimating CO and TPR.
• To evaluate these methods across various gravitational conditions (1 G, 0 G, 1.8 G).
• To identify reliable noninvasive techniques for cardiovascular monitoring in space.

Main Methods:

• Peripheral arterial blood pressure signals from 8 subjects were analyzed during parabolic flights.
• CO and TPR were simultaneously measured using an inert gas rebreathing technique for reference.
• Estimation methods were evaluated using root-normalized mean square errors and Bland-Altman plots.

Main Results:

• The corrected impedance method demonstrated the lowest estimation errors for both CO (20.0%) and TPR (23.5%) across all tested gravity levels.
• Mean arterial pressure was identified as a potential indicator for CO in microgravity, with a 24.5% error.
• Performance varied among methods, with some showing gravity-dependent accuracy.

Conclusions:

• The corrected impedance method offers reliable, low-error estimation of CO and TPR in varying gravity.
• Mean arterial pressure shows potential for CO monitoring specifically in microgravity environments.
• Further validation is needed, but these findings support the development of noninvasive space health monitoring tools.