Air plethysmography: an alternative method for assessing peripheral circulatory adaptations during spaceflights

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Biomedical Engineering

Background:

• Peripheral vascular hemodynamics are altered in microgravity.
• Existing methods for studying these changes in space are limited.
• Understanding vascular deconditioning is crucial for astronaut health.

Purpose of the Study:

• To introduce and validate air plethysmography (AP) as a novel method for assessing peripheral vascular hemodynamics in microgravity.
• To describe the AP device and measurement protocol.
• To evaluate the reproducibility and correlation of AP with a reference method.

Main Methods:

• Development of an air plethysmography (AP) device for limb measurements.
• Establishment of a measurement protocol for AP.
• Comparative study of AP against mercury strain gauge plethysmography (MSGP) in the laboratory.
• Preliminary data collection on the Mir Space Station.

Main Results:

• AP demonstrated good reproducibility for venous capacity, arterial flow index, and half-emptying time (CV < 12%).
• AP results showed good correlation with MSGP for venous capacity (r=0.8), arterial flow index (r=0.7), and half-emptying time (r=0.9).
• While correlated, AP measurements did not perfectly agree with MSGP, indicating it as an alternative rather than a direct replacement.

Conclusions:

• Air plethysmography (AP) is a viable and reproducible technique for quantifying peripheral vascular hemodynamics in microgravity.
• AP measurements correlate well with established laboratory methods.
• This method is expected to enhance the study of vascular deconditioning in weightlessness.