Gender differences in blood pressure control during simulated microgravity
29 May 2013

Two years after the first man went into space, Yuri Gagarin in 1961, Valentina Terechkova became the first woman to board a space flight. As of January 3, 2013, 530 persons participated to a space mission, of which only 56 were women, although they represent approximately 20 % of the astronaut corps.

Valentina Terechkova, the first women in a spaceflight, in 1963

Gender differences in spaceflight studies

In spaceflight, most studies are conducted on men and very few studies have focused on gender differences.

Dr. Natalia N. Arzeno from the Wyle Science, Technology and Engineering Group in Houston, Texas, carried out a study in collaboration the NASA, which was published recently in the American Journal of Physiology (Heart and Circulatory Physiology) in an article entitled "Sex differences in blood pressure control during 6° head-down tilt bed rest"(1).

This article investigates adrenergic, baroreflex, and autonomic indices during continuous infusions of vasoactive drugs in men and women during a 60-day head-down bed rest.
The study was motivated by gender differences in post-spaceflight orthostatic hypotension. Subjects were infused Phenylephrine (PE) and sodium nitroprusside (SNP) to induce blood pressure changes and detect the differences in blood pressure control during long-duration bed rest.

NOTOCORD-hem™ and space-related experiments

The ECG and respiration were acquired with a Medical Data Electronics system and blood pressure was acquired with a Finometer. All signals were recorded using NOTOCORD-hem™ and analyzed offline using custom programs in MATLAB®. Processing and analysis of NOCOTORD-hem™ and MATLAB® data streams are possible in both environments using our library of functions MPI10a.

The conclusion of the article indicates that long-duration bed rest suppresses parasympathetic modulation and baroreflex function in men and women, with women experiencing a larger decrease in baroreflex sensitivity than men after 30 days of bed rest.

During PE infusions, women experienced saturation of the R-R interval high frequency (RR HF) whereas men did not, revealing a gender difference in the parabolic relationship between RR HF, thus reaching the respiratory sinus arrhythmia ceiling at a lower R-R interval than men.
This gender difference in the time course of baroreflex dysfunction could potentially contribute to gender differences in orthostatic tolerance after bed rest.

This study represents a step forward towards the comprehension of the gender difference and emphasizes the need to pursue such investigations in long-duration spaceflight.

Earth viewed from space

It is not the first time that NOTOCORD® is involved in a space-related project. Since 1994, our software technologies have been used by Dr. Anne Pavy-LeTraon (2) from MEDES / Rangueil Toulouse Hospital for human cardiovascular explorations.

We also took part in the Cardiomed mission, a set of experiment to study the impact of the microgravity on human body, with a focus on the medical monitoring of the astronauts on board of the International Space Station.
NOTOCORD® is interfaced to Cardiomed ground segment to contribute to offline analysis of recorded experiments.
The Cardiomed system is developed in a Franco-Russian convention framework between CNES (Centre national d'Etudes Spaciales, a French space agency) and IMBP (Institute for Biomedical Problems).

Our modules for such studies

Here are some of our modules that could be of interest for that type of studies:

► BRS10a : Baroreflex sequence analyzer

  • Automated online detection of spontaneous baroreflex sequences
  • Ascending and descending sequences discrimination
  • Linear regression slope and correlation coefficient computation
  • Baroreflex Effectiveness Index (BEI) computation

► CSA10a : Cross-spectrum analyzer

  • Automated online cross-spectrum analysis between 2 continuous or discrete signals
  • User-defined analysis window duration and averaging
  • User-defined frequency bands selection
  • Cross-spectrum coherence, gain and phase computation
  • Individual spectrum computation for each signal

► SPA10a : Spectral analysis of continuous and discrete signals

  • Spectral analysis using Fourier transform or autoregressive method
  • User-defined analysis window duration and average computation
  • User-defined selection of frequency bands
  • Computation of absolute and relative power for each defined frequency band
  • Continuous display of spectra along with raw signal on a universal chart display

A little guess...

Wondering how many people are currently in the space ?
Click on the astronaut below to discover the correct answer !

(1) Arzeno NM, Stenger MB, Lee SM, Ploutz-Snyder R and Platts SH. Sex differences in blood pressure control during 6° head-down tilt bed rest. Am J Physiol Heart Circ Physiol. 2013 Apr 15;304(8):H1114-23.
(2) Pavy-Le Traon A, Heer M, Narici MV, Rittweger J and Vernikos J. From space to Earth: advances in human physiology from 20 years of bed rest studies (1986-2006).Eur J Appl Physiol. 2007 Sep;101(2):143-94.