Cardiovascular health is influenced by many factors in normal daily life on the International Space Station. The microgravity environment dramatically changes the normal head-to-foot blood pressure gradient, causing crew to experience much higher sustained blood pressure (BP) at the brain. Normal daily life on ISS involves much lower physical activity levels, and together with the BP gradient changes are responsible for microgravity-specific structural adaptations of the heart and blood vessels compared to daily life on Earth. Changes in cardiac mass have been identified with space flight as well as bed rest and there is recent evidence of functional change in cardiac contraction as well as relaxation from bed rest studies. Arterial and venous blood vessel wall architectural properties are changed with bed rest and a recent observation indicated that arteries are stiffer during and for at least 6-days after prolonged spaceflight on ISS. These observations collectively have functional significance in terms of performance of physical work tasks or return to an upright posture after 6-months on ISS, and they might also indicate long-term or permanent cardiovascular health consequences. This is particularly relevant for future interplanetary exploration as well as on Earth where many cultures are tending to adopt increasingly sedentary lifestyles. Therefore, it is essential to gain a thorough knowledge of the cardiovascular adaptations to spaceflight and of the cardiovascular risk factors associated with prolonged weightlessness in order to establish appropriate countermeasures to maintain cardiovascular function and to mitigate if not prevent the onset of overt cardiovascular disease.
The aim of this investigation is to measure and quantify cardiac and vascular structural and functional changes and to observe biomarkers during 6-months of spaceflight and up to one year of recovery. The specific goals of this study are to collect data on the following:
The extended recovery measurements up to 12-months after landing of key variables post-flight will provide new insight into possible long-term consequences of spaceflight.
APPROACH:
Sample/Data collection will be accomplished preflight, postflight, and inflight in sessions described below.
Blood and Saliva Sessions: Blood and saliva will be collected from subjects after an overnight fast and before teeth are brushed. Blood samples will be collected into standard blood collection tubes from the antecubital vein following standard clinical procedures. Saliva samples will be collected after the blood, using commercially available and clinically standard “salivettes”, which are small, sterile, single use pieces of cotton designed to be chewed then frozen until analysis. There will be two sessions preflight between L-90 (Launch minus 90 days) and L-60 at least 2 days apart, six sessions postflight at R+0 (Return to Earth plus 0 days), R+3, R+11 to R+17, R+25 to R+31, R+51 to R+63, and R+1 year, and two sessions inflight between R-30 and R-1, at least 2 days apart.
24-hr Ambulatory Monitoring Sessions: The subject will don the blood pressure cuff on the upper arm, and clip the main unit at the waist. A technician will turn on and verify that the unit is operating properly. The subject will wear the device for 24 hours while engaging in normal daily activity and then remove it. There will be one session preflight between L-90 and L-60, four sessions postflight at R+3, R+11 to R+17, R+25 to R+31, and R+1 year, and three sessions (one optional) inflight at L+20 to L+40, R-30 to R-1, L+90 to R-31 (optional).
Resting Ultrasound Sessions: The subject will complete a questionnaire or log regarding recent exercise and medication history. Instrumentation will be followed by resting ultrasound images of the heart (cardiac echosonography study) and blood vessel wall detail, splanchnic blood pooling, thyroid dimensions, inferior vena cava lumen diameter and velocity captured while in the supine position. A pulse tonometer will be placed against the skin of the neck to collect a pulse pressure signal from the carotid artery. A blood pressure cuff will be wrapped around and inflated to occlude flow to the forearm for five minutes while ultrasound measurements are taken for an additional 3 min. The subject will then move to a seated position and ultrasound images of the heart, blood vessel walls will be repeated. The measurements of ECG, continuous finger BP, brain blood flow and cardiac output will be collected. The ultrasound images will be time-aligned during this session with the digital data collection file collected simultaneously. The digital file will, itself, contain time-matched, beat-by-beat digitized signals for the following variables: pulse tonometry, ECG, and continuous finger BP, brain blood flow and cardiac output. The latter two variables will be measured by Doppler ultrasound. There will be one session preflight between L-90 and L-60, four sessions postflight (2 optional) at R+3 or R+4, R+11 to R+17, R+51 to R+63 (optional), and R+1 year (optional), and two sessions inflight at L+20 to L+40 and R-30 to R-1. The R-30 to R-1 session may include optional add-on views if resources are available.
Exercise Ultrasound Sessions: The subject will lie supine for instrumentation of a 3-lead electrocardiogram (ECG) and a finger blood pressure cuff. The subject will complete a questionnaire or log regarding recent exercise and medication history. Ultrasound probes will be placed against the skin of the thigh and fixed in place with Velcro straps. Baseline lumen diameters and blood flow velocity of the superficial femoral and tibial arteries will be collected. The subject will complete leg squat exercises that will increase blood flow velocity to meet the metabolic demands of moderate exercise. Five minutes of post-exercise ultrasound data will be collected to observe the rate of recovery as an index of arterial function followed by de-instrumentation. There will be one session preflight between L-90 and L-60, four sessions postflight (2 optional) at R+3 or R+4, R+11 to R+17, R+51 to R+63 (optional), and R+1 year (optional), and two sessions inflight at L+20 to L+40 and R-30 to R-1.
Leg Cuff Ultrasound Sessions: The subject will complete a questionnaire or log regarding recent exercise and medication history. A partial leg occlusion test will be administered to reflect the equivalent of 30 mmHg compression of the thigh. Ultrasounds will be completed as for the Resting Ultrasound Session. After donning Braslets cuffs, the subject will return after three hours, when the ultrasounds will be repeated and timed to occur just before/just after the occlusion is released. There will be one session preflight between L-90 and L-60, and if resources allow, one optional session inflight at L+60 to L+120.
RESULTS:
Results for this investigation are unavailable. This is an international experiment. NASA does not currently have an agreement with international space partners to archive their data in the LSDA.