Monitoring of the cardiac and vascular response to LBNP during the 14 day spaceflight "Cassiopee".

The objective of the present experiment was to monitor in real time the cardiac and the peripheral response to inflight LBNP. The second objective was to detect and quantify hemodynamic signs of orthostatic tolerance inflight by measuring the heart rate, blood pressure, cardiac and regional hemodynamics during LBNP.

Cardiac hemodynamics at rest and during LBNP after 4 days and 6 weeks in HDT.

The first objective was to assess the left ventricle function at rest, at the end of a short term (4 days) HDT, and at the end of a long term (6 weeks) HDT. The second objective was to check if these short and long HDT induced any abnormal cardiac hemodynamic response to LBNP (lower body negative pressure) test that could be related to orthostatic intolerance.

Heart, and peripheral arteries and veins during the 14 month MIR space flight.

NASA: Ultrasound Doppler imaging and electrocardiography were used to study hemodynamic responses to spaceflight onboard the Mir space station. Cardiovascular adaptation was studied at rest and during the use of thigh cuffs or "Bracelets" for weightlessness countermeasures. Specific changes in hemodynamic parameters are presented and discussed, along with an evaluation of the effectiveness of the Bracelet countermeasures.^ieng

Hemodynamic response to LBNP during the 14 month MIR spaceflight (94-95).

NASA: Lower body negative pressure (LBNP) was used during the Mir spaceflight in a study of orthostatic tolerance. Hemodynamic responses were measured including heart rate, blood pressure, cerebral artery blood flow, and lower limb vascular resistance. Results showed that femoral flow volume decreased, which may be due to hypovolemia and reduced cardiac output. Additional changes in femoral vascular response and cerebral to femoral blood flow are discussed.^ieng

Cardiac and vascular adaptation to 0g with and without thigh cuffs (Antares 14 and Altair 21 day Mir spaceflights).

UNLABELLED: Cardiovascular adaptation was evaluated on 2 astronauts: one wearing thigh cuffs from flight day 1 to 8 (14d flight), the second without cuffs (21d flight). Ultrasound investigations were performed at rest and during LBNP. RESULTS: Without thigh cuffs the cardiovascular adaptation consists in (1) the development of a hypovolemia with an increase of the heart rate and the cardiac output, (2) the decrease of the vascular tone in the deep (mesenteric and splanchnic) and peripheral (Lower limbs) vascular areas. The use of thigh cuffs maintains the volemia and the cardiac output at the preflight level (without heart rate increase) and prevents the loss of vascular tone in the deep and peripheral areas. Moreover the adaptative process changes since the cuffs are removed and even the volemia seems to be unaffected at this stage the vascular tone decreases to a comparable extend as during the flight without cuffs. Nevertheless during the flight without cuffs or 3 days after removing the cuffs hemodynamic signs of decreased orthostatic tolerance are present during the inflight and the 3 days post flight LBNP. Presently the possible contribution of the thigh cuffs to the reduction of the vascular deconditioning has not been tested yet.

Influence of the thigh cuffs countermeasure on the cardiovascular adaptation to 0.g (14 and 21 day Mir spaceflights).

Assess the 0.g induced cardiac and vascular changes at rest on two cosmonauts: one using thigh cuffs from flight day 1 to 8 (Mir 14d flight) the second one not using thigh cuffs (Mir 21d flight). Both were not using intensively any other countermeasure. The ultrasound device onboard Mir with Echo, Doppler, and TM, modes was used.

Assessment of the inflight cardiovascular adaptation & deconditioning. (14 day Antarès spaceflight).

Objectives & method: (1) assess the main cardiac and vascular hemodynamic changes induced by the 0.g. (2) evaluate, the astronaut orthostatic tolerance, inflight, using LBNP. The ultrasound device "As.de.Coeur" with Echo, Doppler, TM, & plethysmograph modes was used.

Effect on the cardiac function of repeated LBNP during a 1-month head down tilt.

Cardiovascular assessment by ultrasound methods was performed during two long duration (1 month) Head Down Tilt (HDT) on 6 healthy volunteers. On a first 1 month HDT session, 3 of the 6 subjects (A, B, C) had daily several lower body negative pressure tests (LBNP), whereas the 3 subjects remaining (D, E, F) rested without LBNP. On a second 1 month HDT session subjects D, E, and F had daily LBNP tests and the A, B and C subjects did not. The cardiac function was assessed by Echocardiography, (B mode, TM mode). On all the "6 non LBNP" subjects the left ventricule diastolic volume (LVDV), the stroke volume (SV) and the cardiac output (CO) increase (+10%, -15%) after HDT then decrease and remain inferior (-5%, -5%) or equal to the basal value during the HDT. Immediately after the end of the HDT the heart rate (HR) increase (+10%, +30%) whereas the cardiac parameters decrease weakly (-5%, -10%) and normalize after 3 days of recovery. On the "6 LBNP" subjects the LVDV, SV and CO increase (+10%, 15%) after 1 h HDT as in the previous group then decrease but remain superior (+5%, +15%) or equal to the basal value. After the HDT session, the HR is markedly increased (+20%, +40%) the LVDV and SV decrease (-15%, -20%) whereas the CO increases or decreases depending on the amplitude of the HR variations. These parameters do not completely normalize after 3 day's recovery. Repeated LBNP sessions have a significant effect on the cardiovascular function as it maintains all cardiac parameters above the basal value. The LBNP manoeuvre can be considered as an efficient countermeasure to prevent cardiac disadaptation induced by HDT position and probably microgravity.

Visualization of the fetal circle of Willis and intra-cerebral arteries by color-coded Doppler.

We report here the visualization of the intra-cerebral vessels in a normal fetus of 28 weeks gestational age, by color-coded Doppler. The color-flow mapping method makes it possible to identify very small vessels that up to date could not be detected on B-mode imaging, and will permit new clinical and physiological studies of the circulation in specific areas of the fetal brain.