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Noninvasive Hemodynamic Monitoring in Microgravity, Phase II (Arterial Stiffness)

Completed Technology Project

Project Introduction

Noninvasive Hemodynamic Monitoring in Microgravity, Phase II (Arterial Stiffness)
Microgravity-induced changes in cardiovascular physiology are well-known and significant. Even short duration flights can lead to orthostatic intolerance, syncope, and reduced maximal oxygen uptake upon return to Earth. In long-duration missions, these effects can lead to significant cardiovascular deconditioning, which poses unnecessary health and safety risks to astronauts. Countermeasures, such as exercise or lower body negative pressure application are typically used to mitigate these effects. However, there is still a need for simple methods to monitor and quantify cardiovascular alterations and the effectiveness of the countermeasures, as shown in the NASA Bioastronautics Roadmap. Our team has developed a non-invasive hemodynamic monitor based on the measurement of the ballistocardiogram (BCG) (reaction forces due to blood flow) using a weighing scale for the purpose of detecting cardiovascular alterations in multi-g environments. In our 2012-2013 campaign, we demonstrated that scale-based BCG measurements could be acquired in microgravity (0g) and on Earth (1g) without loss of signal quality, which is the first demonstration to our knowledge. This type of instrument is fully compatible with anticipated and existing commercial and government capsules and winged space vehicles. The previous multi-g characterization study enabled us to leverage more than five years of clinical studies on Earth, where several disease states and cardiovascular changes have been characterized. This BCG-scale system has been tested in multiple clinical trials at Stanford Hospital and the VA System, and is effective in monitoring changes in cardiac output, contractility, and for congestive heart failure assessment. More recently, this BCG-scale was modified with an additional sensor and validated with human subject studies to directly measure arterial stiffness via Pulse Wave Velocity (PWV), and monitor longitudinal changes in PWV. Arterial stiffness changes have predictive power in determining orthostatic intolerance (OI) in astronauts. Therefore, with the sensor addition, this BCG-scale system now provides a comprehensive assessment of OI by non-invasively monitoring both cardiac and vascular changes, simply by standing on the scale. Compared to other BCG monitors based on the recording of the free-floating body acceleration, this system allows recording both on the ground and in microgravity. This system also requires less cabin volume than in free-floating measurements, as demonstrated on our previous campaign. Therefore, data measured in weightless environments can be compared to the large body of data that has been gathered on the ground, significantly facilitating the validation of the method. Moreover, this platform enables the comparison of free-floating acceleration BCG to scale-based BCG, therefore providing a means to compare current studies of free-floating acceleration BCG (such as the ESA-sponsored B3D program) with ground-based studies something currently not possible. We propose to further develop this technology and demonstrate its usefulness in microgravity in a series of parabolic flights for measuring PWV. By flying a clinically-tested device used in many ground-based trials, we will be able to establish a correlation between ground-based and microgravity measurements in arterial stiffness. With the completion of this proposed campaign, we expect to present a compact and simple-to-use device to NASA capable of detecting cardiovascular alterations which can be used on the ISS, and long duration space and planetary missions. More »

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