Increased G-suit coverage improves cardiac preloading conditions during positive pressure breathing

Area of Science:

• Cardiovascular Physiology
• Aerospace Medicine
• Nuclear Cardiology

Background:

• Positive pressure breathing (PPB) is used in aerospace to aid respiration.
• Anti-G suits are worn to counteract G-forces, but their effect on cardiac function during PPB is not fully understood.
• Assessing left ventricular function during dynamic physiological challenges requires sensitive imaging techniques.

Purpose of the Study:

• To compare the effects of extended-coverage (EC) vs. standard-coverage (SC) anti-G suits on left ventricular function during PPB.
• To evaluate the utility of miniaturized nuclear probe (MNP) imaging and radionuclide cardiac blood pool imaging (RCBI) for assessing cardiac response to PPB.

Main Methods:

• Seven subjects underwent exposure to 4.0 and 9.3 kPa PPB while wearing EC and SC anti-G suits.
• Left ventricular function was assessed using MNP and RCBI.
• Measurements included ejection fraction, diastolic filling, end-diastolic volume, and end-systolic volume.

Main Results:

• Ejection fraction remained unchanged with both suit types and imaging techniques.
• The atrial contribution to diastolic filling was significantly greater with the SC suit.
• MNP showed greater non-linear declines in end-diastolic and end-systolic volumes over time with the SC suit.
• Left ventricular preload decline during PPB was attenuated with increased G-suit coverage.

Conclusions:

• Increased anti-G suit coverage attenuates left ventricular preload decline during PPB.
• MNP is more sensitive than RCBI for detecting non-steady-state cardiac physiological changes during PPB.
• EC anti-G suits may offer better cardiovascular support during PPB compared to SC suits.