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.
1
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.To read this article in full you will need to make a payment
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Article Info
Publication History
Accepted:
August 3,
2001
Received in revised form:
August 3,
2001
Received:
June 20,
2001
Identification
Copyright
© 2001 Excerpta Medica Inc. Published by Elsevier Inc. All rights reserved.
