| Significant changes to the cardiovascular system occur during long duration spaceflight; a reduction in cardiac reserve could impact the ability of a crew-member to fulfill mission requirements or respond to a contingency. Cardiovascular fluid redistribution occurs during equilibration to microgravity and may be partially responsible for changes in cardiovascular performance. The Russian Bracelet-M device is currently manifested on the International Space Station (ISS) to reduce venous return to the heart and simulate a microgravity hypo-volemic state. This system may reduce cardiac preload and increase lower extremity venous pressure causing interstitial fluid shifts and changes in venous compliance. Although subjective improvement has been seen in some users, a quantitative measurement of the cardiovascular and venous effects of this device have not been extensively investigated on the ground or in space. Using the Onboard Proficiency Enhancement (OPE) program developed by the ADUM team and exploiting recent advances in ultrasound technology, the investigation of the acute effects of Bracelet device is possible. We hypothesized that the device increases fluid sequestration in the lower extremities inducing a relative hypo-volemia in the central circulation compared to what is typically observed in a microgravity environment.
This proposal enhanced the collaboration of an international team of experts (Russia/USA) in conducting ground, simulated microgravity, and flight experiments to answer three specific aims:
1. Evaluate the vascular and cardiac effects of the Bracelet-M device in ground based studies using ultrasound in combination with the current system of device calibration, user training, and application.
2. Investigate the human factors, level of experience, and training necessary to perform focused vascular and echocardiography exams in a ground and microgravity environment using real-time remote guidance of inexperienced ultrasound operators.
3. Determine the physiologic effects of the Bracelet-M device on the cardiovascular system during simulated microgravity and flight experiment with recommendations for optimal use protocols with a predictable effect and an increased margin of safety.
Ultrasound is a terrestrial standard of care for assessing cardiovascular function. This proposal developed just-in-time training methodologies, combined with remote guidance, to allow non-expert operators to use ultrasound to evaluate the cardiovascular system and the effects of the Bracelet device on venous loading, vascular capacitance and cardiac performance. This proposal provided essential medical information and capabilities to facilitate exploration class missions. Specifically this proposal developed and validated procedures for the expanded diagnostic use of ultrasound for cardiovascular medical conditions which may occur on the International Space Station and future exploration class missions.
Two primary objectives of this proposal were to obtain baseline information regarding the use of ultrasound to monitor cardiovascular alterations which occur during microgravity exposure and to evaluate the physiologic effects of the Bracelet device. The experimental team developed a rapid training program to allow minimally trained operators to obtain high quality ultrasound images of the cardiac and vascular system, with or without maneuvers to assess the effects of the Braslet device on the vascular system. There was a significant and profound effect of Braslet occlusion on the peripheral and vascular system which caused alterations in cardiac function. This countermeasure device may have therapeutic potential for space adaptation, treatment of vascular disorders in a microgravity environment, and potentially to improve readaptation to a gravity environment.