HEART - Physiological Parameters That Predict Orthostatic Intolerance After Spaceflight
ISS 8S (Soyuz TMA-4) Dutch "Delta" Mission
|(1)||Academic Medical Center M01-08|
University of Amsterdam
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This experiment will provide further data already obtained from similar research performed on the Belgian Soyuz Mission Odissea of ESA astronaut Frank De Winne in 2002, and the Spanish Soyuz Mission Cervantes of ESA astronaut Pedro Duque in 2003.
The objective is to predict orthostatic intolerance, i.e. the inability to stand upright, of astronauts who have spent a long period in a weightless environment. Orthostatic intolerance is defined as the inability to stand for 10 minutes. The predictions will be based on the measurements of physical parameters such as blood pressure, electrocardiograms, thoracic impedance and brain blood flow by ultrasound. This data will serve as input for the characteristics of a particular subject into a computer model of the circulation
The definition of physiological parameters may serve to pinpoint those subjects that have poor orthostatic tolerance under unfavourable conditions. This may, eventually, help in diagnosis of unexplained faints in patients.
CIRCA - One-day (24-hour) pattern of blood pressure and heart rate in weightlessness
ISS 8S (Soyuz TMA-4) Dutch "Delta" Mission 2004
BMI - Blood pressure circadian rhythms in weightlessness
ISS 7S (Soyuz TMA-3) Spanish "Cervantes" Mission 2003
Blood pressure Measurement Instrument (BMI)
ISS 4S (Soyuz TM-34) Italian "Marco Polo" Mission 2002
The astronauts are tested pre-flight and post-flight in a ground-based lab using a computerised tilting table that can induce a variety of dynamic tilt manoeuvres. These parameters will act as predictors for the outcome of the test, where astronauts are asked to stand relaxed, leaning against a wall for a maximum of 10 minutes.
In five cosmonauts, we measured finger arterial pressure noninvasively in supine and upright positions. Preflight measurements were repeated using venous occlusion thigh cuffs to impede venous return and "trap" an increased blood volume in the lower extremities; postflight sessions were between 1 and 3 days after return from 10- to 11-day spaceflight. BaroReflex Sensitivity (BRS) was determined by spectral analysis and by PRVXBRS, a time-domain BRS computation method.
Although all completed the stand tests, two of five cosmonauts had drastically reduced pulse pressures and an increase in heart rate of ∼30 beats/min or more during standing after spaceflight. Averaged for all five subjects in standing position, high-frequency interbeat interval spectral power or transfer gain did not decrease postflight. Low-frequency gain decreased from 8.1 (SD 4.0) preflight baseline to 6.8 (SD 3.4) postflight (P = 0.033); preflight with thigh cuffs inflated, low-frequency gain was 9.4 (SD 4.3) ms/mmHg. There was a shift in time-domain-determined pulse interval-to-pressure lag, Tau, toward higher values (P < 0.001). None of the postflight results were mimicked during preflight venous occlusion. In conclusion, two of five cosmonauts showed abnormal orthostatic response 1 and 2 days after spaceflight. Overall, there were indications of increased sympathetic response to standing, even though we can expect (partial) restoration of plasma volume to have taken place. Preflight venous occlusion did not mimic the postflight orthostatic response.
Blood pressure (BP)-levels in Space were not very much changed from preflight; the circadian BP-rhythm seemed dampened. Only daytime diastolic pressures (both subjects) and nighttime HR (one subject) were significantly lower in Space. However, compared to the effect of a control tilt manoeuvre on the ground, even lower BP values might have been expected. Striking were the BP- and HR-surges during the working days in Space, often related to stressful moments like live appearances on public TV. Systemic vascular resistance (SVR) dropped during the night, unlike HDT. Thus, actual spaceflight refuted our earlier findings in HDT both for BP-levels and for daytime to nighttime changes.
The combined observations lead to the hypothesis that short-lasting spaceflight may induce strong psychological stress in astronauts. When interpreting space-physiological observations this must be taken into account.
|For a very comprehensive overview on the first six ESA missions to the ISS, please, consult the following reference document - see also document no. 10 in the list of references above:
The National - ESA Soyuz missions Andromède, Marco Polo, Odissea, Cervantes, Delta and Eneide;
Jack J. W. A. van Loon, F. Javier Medina, Hilde Stenuit, Eric Istasse, Marc Heppener and Roberto Marco;
Microgravity Science and Technology;
Volume 19, Numbers 5-6 (2007), 9-32, DOI: 10.1007/BF02919448|
Patrik Sundblad (e-mail: email@example.com)