WISE-2005: Changes in orthostatic response throughout menstrual cycle.
- Paper number
IAC-08.A1.2.4
- Author
Ms. Heather Edgell, University of Waterloo, Canada
- Coauthor
Mrs. Danielle Greaves, University of Waterloo, Canada
- Coauthor
Dr. Richard Hughson, University of Waterloo, Canada
- Coauthor
Dr. Philippe Arbeille, Centre Hospitalier Universitaire Trousseau, France
- Coauthor
Dr. Alan Hargens, University of California at San Diego, United States
- Year
2008
- Abstract
Women are more susceptible to orthostatic intolerance (OI) on return from space flight or after bed rest than men. The WISE campaigns of 2005 studied the effects of 60 days of 6o head-down bed rest (HDBR) on women. One protocol involved 80o head-up tilt (HUT) for 10 minutes followed by increasing levels of lower body negative pressure (LBNP) in this position until pre-syncope. At this point LBNP was stopped and the table returned to horizontal. Pre-syncope was defined by a drop in systolic blood pressure to less than 70mmHg. For these tests all performed before HDBR, 5 women were menstruating (MENS), 8 women were in the follicular phase of menstruation (F; from end of MENS to day 12), and 9 women were in the luteal phase of menstruation (L; from day 18 to beginning of MENS). During MENS estrogen and progesterone are low, during F estrogen is high and progesterone is low, and during L both estrogen and progesterone are high. Mean arterial pressure (MAP), heart rate (HR) and cardiac output (Q) (Finometer) were all measured throughout the test. In all 3 groups, MAP decreased with the greatest drop in L (MENS: 87.4±3.9mmHg to 39.2±6.1mmHg; F: 88.3±2.0mmHg to 41.9±5.8mmHg; L: 91.8±3.2mmHg to 37.6±1.6mmHg; Interaction P=0.019), HR increased with a trend for a greater increase in F (MENS: 67.6±2.9bpm to 120.0 ± 9.4bpm; F: 70.2±3.9bpm to 142.7 ± 6.6bpm; L: 67.5±2.1bpm to 126.6 ± 7.6bpm; Interaction P=0.305) and Q decreased in all phases (MENS: 5.6±0.4L/min to 3.4±0.4L/min; F: 5.6±0.6L/min to 3.3±0.3L/min; L: 5.8±0.3L/min to 3.2±0.3L/min). There was also increased plasma norepinephrine (MENS: 203.7±49.0pg/mL to 666.0±115.6pg/mL; F: 168.1±22.4pg/mL to 710.1±94.6pg/mL; L: 177.0±28.7pg/mL to 803.1±145.3pg/mL) and epinephrine (MENS: 10.2±2.0pg/mL to 44.1±8.8pg/mL; F: 19.4±5.4pg/mL to 62.3±8.6pg/mL; L: 12.3±1.9pg/mL to 54.3±14.4pg/mL). There were no significant differences in tolerance time between MENS, F and L (P=0.423); although tolerance was slightly less during MENS (MENS: 21.2 ± 1.4 min; F: 23.6 ± 1.0 min; L: 23.1 ± 1.2 min). Since the powers of the ANOVAs were below the required power of 0.8, a greater sample number may help to clarify these results. These results suggested different responses to orthostatic stress throughout the menstrual cycle, and are thus important to consider for all future cardiovascular studies involving women. Funding provided by the CSA, NASA, ESA, and CNES.
- Abstract document
- Manuscript document
IAC-08.A1.2.4.pdf (🔒 authorized access only).
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