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Effect of spaceflight on cardiovascular responses to upright posture in a 77-year-old astronaut

      During spaceflight the cardiovascular system undergoes changes that result consistently in orthostatic hypotension and syncope or presyncope after landing. Recently, we were afforded the opportunity to document cardiovascular responses to standing before and after a 10-day spaceflight in a 77-year-old man and compared them with responses previously documented in younger male astronauts. The study was approved by the Johnson Space Center Investigational Review Board. Data were collected 10 days before launch, 2 hours after landing, and 3 days after landing. Before each test, the subject abstained from caffeine, alcohol, and any medication for the preceding 12 hours, was ≥2 hours postprandial, and had not exercised heavily in 24 hours. The subject was laid on a tilt table, and instrumented for electrocardiogram, manual blood pressure (sphygmomanometer), and finger arterial pressure (Finapres, Ohmeda, Inglewood, Colorado). A catheter was inserted into an antecubital vein. After a 20-minute supine period, a blood sample was drawn for determination of plasma norepinephrine and epinephrine levels. Plasma volume was determined using carbon monoxide rebreathing.
      • Maas A.H.J.
      • Hamelink M.L.
      • de Leeuw R.J.
      An evaluation of the spectrophotometric determination of Hb02, HbC0, and HB in blood with the co-oximeter IL 182.
      Two-dimensional and M-mode echocardiography were used to determine aortic cross-sectional diameter and Doppler ultrasound was used to measure beat-to-beat aortic flows. The hand to which the Finapres was attached was strapped to an arm board so that it would remain at heart level in both the supine and upright positions. Continuous baseline measurements were made for 5 minutes in the supine position and continued while the tilt table was raised to 80° upright. The subject was kept in the upright position for 10 minutes, after which a final blood sample was drawn for plasma norepinephrine and epinephrine levels. Echocardiographic images were recorded on videotape and analog data were recorded on digital tape and paper recorders for later analyses.
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