Future long-duration human spaceflight will require developments to limit biocontamination of sur... more Future long-duration human spaceflight will require developments to limit biocontamination of surface habitats. The MATISS (Microbial Aerosol Tethering on Innovative Surfaces in the international Space Station) experiments allowed for exposing surface treatments in the ISS (International Space Station) using a sample-holder developed to this end. Three campaigns of FDTS (perFluoroDecylTrichloroSilane) surface exposures were performed over monthly durations during distinct periods. Tile scanning optical microscopy (×3 and ×30 magnifications) showed a relatively clean environment with a few particles on the surface (0.8 to 7 particles per mm2). The varied densities and shapes in the coarse area fraction (50–1500 µm2) indicated different sources of contamination in the long term, while the bacteriomorph shapes of the fine area fraction (0.5–15 µm2) were consistent with microbial contamination. The surface contamination rates correlate to astronauts’ occupancy rates on board. Asymmetric...
Objective: Body mass (BM) loss and body composition (BC) changes threaten astronauts' health and ... more Objective: Body mass (BM) loss and body composition (BC) changes threaten astronauts' health and mission success. However, the energetics contribution of the exercise countermeasure to these changes has never been investigated during long-term missions. We studied energy balance and BC in astronauts during 6-month missions onboard the International Space Station. Methods: Before and after at least 3 months in space, BM, BC, total and activity energy expenditure (TEE and AEE) were measured using the doubly labeled water method in 11 astronauts (2011-2017). Physical activity (PA) was assessed by the SensewearPro® activity-device. Results: Three-month spaceflight decreased BM (-1.20kg (SE 0.5); P=0.04), mainly due to non-significant fat-free mass loss (FFM;-0.94kg (0.59)). The decrease in walking time (-63.2min/day (11.5); P<0.001) from preflight was compensated by increases in non-ambulatory activities (+64.8min/day (18.8); P<0.01). Average TEE was unaffected but a large interindividual variability was noted. Astronauts were stratified into those who maintained (stable_TEE; n=6) and those who decreased (decreased_TEE n=5) TEE and AEE compared to preflight data. Although both groups lost similar BM, FFM was maintained and FM reduced in stable_TEE astronauts, while FFM decreased and FM increased in decreased_TEE astronauts (estimated between-group-difference (EGD) in ΔFFMindex [FFMI] 0.87kg/m 2 , 95%CI +0.32 to +1.41; P=0.01, ΔFMindex [FMI]-1.09kg/m 2 , 95%CI-2.06 to-0.11kg/m 2 ; P=0.03). The stable_TEE group had higher baseline FFMI, and greater baseline and inflight vigorous PA than the decreased_TEE group (P<0.05 for all). ΔFMI and ΔFFMI were respectively negatively and positively associated with both ΔTEE and ΔAEE. Conclusion: Both ground fitness and inflight overall PA are associated with spaceflight-induced TEE and BC changes and thus energy requirements. New instruments are needed to measure real-time individual changes in inflight energy balance components.
Future long-duration human spaceflight calls for developments to limit biocontamination of the su... more Future long-duration human spaceflight calls for developments to limit biocontamination of the surface habitats. The MATISS experiment tests surface treatments in the ISS’s atmosphere. Four sample holders were mounted with glass lamella with hydrophobic coatings, and exposed in the Columbus module for ~6 months. About 7800 particles were detected by tile scanning optical microscopy (×3 and ×30 magnification) indicating a relatively clean environment (a few particles per mm2), but leading to a significant coverage-rate (>2% in 20 years). Varied shapes were displayed in the coarse (50–1500 µm2) and fine (0.5–50 µm2) area fractions, consistent with scale dices (tissue or skin) and microbial cells, respectively. The 200–900 µm2 fraction of the coarse particles was systematically higher on FDTS and SiOCH than on Parylene, while the opposite was observed for the <10 µm2 fraction of the fine particles. This trend suggests two biocontamination sources and a surface deposition impacted...
Space environ ment is inherently hostile and dangerous for astronauts. Since extra-vehicu lar act... more Space environ ment is inherently hostile and dangerous for astronauts. Since extra-vehicu lar activity (EVA) should be limited or assisted as much as possible, the significant role of robot ic systems is of notable relevance. Tele-navigation of ground rovers in hostile and unknown environments is one of the applicable p roblems for modern planetary exp loration missions. Pilots involved in these missions should be supported with intelligent and adaptive Hu man-Machine Interfaces (HM Is) able to guarantee a high level of situation awareness and an affordable mental workload. This paper aims to illustrate the approach used to design, test and assess a Remote Control Station (RCS) fo r ground missions. The RCS is used to remotely operate a 4-wheel drive scaled vehicle, representing a min i-rover for space exp loration. The complete system includes the control station and the vehicle, all based on off-the-shelf components. The rover is used as a tool to assess operator"s situation awareness provided through the Graphic User Interface (GUI). This research activity is part of the project STEPSa research project co-financed by Pied mont Region.
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 1999
To clarify whether exposure to 6° head-down tilt (HDT) leads to alterations in body fluid volumes... more To clarify whether exposure to 6° head-down tilt (HDT) leads to alterations in body fluid volumes and responses to a saline load similar to those observed during space flight we investigated eight healthy subjects during a 4-day, 6° HDT and during a time-control ambulatory period with cross-over. Compared with the ambulatory period, HDT was associated with greater urinary excretion of water and sodium (UV, UNaV) from 0 to 12 h (cumulated UV 1,781 ± 154 vs. 1,383 ± 170 ml, P < 0.05; cumulated UNaV 156 ± 14 vs. 117 ± 9 mmol, P < 0.05), and with higher plasma atrial natriuretic factor (ANF) at 4 h. Hemoglobin and hematocrit increased over the first 24 h, and blood and plasma volumes were decreased after 48 h of HDT ( P< 0.05). Plasma renin activity (PRA) and aldosterone did not differ between the two groups. With prolongation of HDT, UV and UNaV returned close to baseline values. On the fourth HDT day, a 30-min infusion of 20 ml/kg isotonic saline was performed, while a large ...
American Journal of Physiology-Heart and Circulatory Physiology, 1998
Changes in autonomic nervous system activity could be linked to the orthostatic intolerance (OI) ... more Changes in autonomic nervous system activity could be linked to the orthostatic intolerance (OI) that individuals suffer after a spaceflight or head-down bed rest (HDBR). We examined this possibility by assessing the sympathetic nervous system activity during 42 days of HDBR in seven healthy men. Heart rate variability was studied with the use of power spectral analysis, which provided indicators of the sympathetic (SNSi) and parasympathetic (PNSi) nervous system influences on the heart. Urinary catecholamines and the spontaneous baroreflex sensitivity were measured. Urinary catecholamines decreased by 21.3%, showing a decrease in SNSi. Heart rate variability was greatly reduced during 42 days of HDBR with a drop in PNSi but with no significant changes in SNSi. The baroreflex sensitivity was greatly reduced (30.7%) on day 42 of HDBR. These results suggest a dissociation between the catecholamine response and the SNSi of the heart rate. This dissociation could be the consequence of a...
The effect of exercise and LBNP countermeasures on the cardiovascular deconditioning response hav... more The effect of exercise and LBNP countermeasures on the cardiovascular deconditioning response have been evaluated by the study of heart rate variability during progressive LBNP tests before, during (day 15), and after 28 d continuous 6 degrees head-down tilt bed rest. Twelve healthy men (age 27-42 years) were studied in two groups. Six were assigned to a countermeasure regime (CM) consisting of strenuous short-term resistance exercise once per day, 6 days per week from day 7 to day 28, combined with lower body negative pressure (LBNP, -28 mm Hg) for 15 min on days 16, 18, 20, and 22-28. Results were compared with data from six subjects, matched on the basis of maximum oxygen uptake, who received no countermeasures (No-CM). The main effects of bed rest were seen in reductions in RR-interval, and in total spectral power. The results of spectral analysis showed a significant reduction in an index of parasympathetic activity with a nonsignificant increase in a sympathetic indicator. The...
Cardiovascular responses to orthostatic tests were studied before and after a prolonged 42 day-he... more Cardiovascular responses to orthostatic tests were studied before and after a prolonged 42 day-headdown bed-rest (HDBR;A6°) experiment simulating a long duration space¯ight. Seven men participating in the experiment underwent stand tests (10 min) and lower body negative pressure (LBNP) tests (5 min at A25, A35, A45 mmHg). Heart rate variability and spontaneous barore¯ex response slope (SBS) were analysed to assess autonomic nervous system responses. Changes in plasma volume (PV) were assessed at the end of HDBR. At the end of HDBR, four subjects could not complete the stand tests and one could not complete the LBNP test. A higher stressed heart rate with standing (+44% before and +57% after HDBR) and LBNP exposure (+19% before and +34% after HDBR) were observed. A decrease in blood pressure (BP) re¯ecting a reduced vasomotor response was only observed with standing (mean BP +21% before and A8% after HDBR); LBNP was less sensitive probably because it was performed 6 h after the stand test. The PV decreased by 10.6%. A decline in spectrum total power re¯ecting a reduced variance of RR-interval, a decrease in parasympathetic activity and an increase in sympathetic one were observed at the end of HDBR. The reduced parasympathetic indicator and SBS would suggest that the vagal nerve component of the cardiovascular control had been diminished. Except for a lower BP when standing after HDBR, no signi®cant dierence was observed between ®nishers and non-®nishers. Autonomic nervous system changes including reduced vasomotor responses constituted important contributors to the orthostatic intolerance observed here and after space¯ights. Some autonomic and PV changes seemed to be opposite to those observed with training and would suggest a role of reduced physical activity in cardiovascular changes induced by HDBR.
Thoraco-cephalic fluid shift induced by weightlessness may influence cerebral autoregulation. Our... more Thoraco-cephalic fluid shift induced by weightlessness may influence cerebral autoregulation. Our objective was to assess effects of simulated weightlessness by a 7-day head-down bed rest (HDBR) on the kinetics of cerebral blood flow (CBF) autoregulation in eight healthy women (27.9 +/- 0.9 years). This was studied by transcranial Doppler (TCD) of the middle cerebral artery (MCA) during the sudden decrease in blood pressure (BP) induced by quickly deflating thigh cuff aftera 4-min arterial occlusion before (D - 3), during (D2, D5) and after the HDBR (D + 1). BP (Finapres) and MCA maximal blood flow velocity were continuously recorded. Cerebrovascular resistance (CR) was expressed as the ratio of mean BP to mean MCA velocity. The CR slope was defined as changes in CR per second during the BP decrease. The magnitude of the relative decrease in mean BP and MCA velocity as well as the CR slope did not differ significantly before, during and after the HDBR, showing no major impairment of cerebral autoregulation during short-term HDBR. The time to maximum decrease in CR (T1 in s), corresponding to the maximum vasodilation was reduced on D2 (7-2 +/- 0.6) versus D - 3 (9.9 +/- 1-3), D5 (9-6 +/- 0.8) and R + 1 (11.7 +/- 11) probably as a result of the fluid shift. We also looked if the responses during the thigh cuff release differed in women according to their tolerance to the 10 min stand test performed after the HDBR: T1 was larger in the five women who presented orthostatic intolerance suggesting that some differences in cerebral autoregulatory responses may be related to orthostatic intolerance.
This new multi-disciplinary medical experimentation center provides the ideal scientific, medical... more This new multi-disciplinary medical experimentation center provides the ideal scientific, medical and technical environment required for research programs and to prepare international space station Alpha (ISSA) missions, where space and healthcare industries can share their expertise. Different models are available to simulate space flight effects (bed-rest, confinement,...). This is of particular interest for research in Human psychology, physiology, physiopathology and ergonomics, validation of biomedical materials and procedures, testing of drugs, and other healthcare related products. This clinical research facility (CRF) provides valuable services in various fields of Human research requiring healthy volunteers. CRF is widely accessible to national and international, scientific, medical and industrial organisations. Furthermore, users have at their disposal the multi-disciplinary skills of MEDES staff and all MEDES partners on a single site.
The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriureti... more The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriuretic factor), electrolytes and creatinine concentrations, and blood pressure were measured in two different four-week experimental protocols: respectively -6 degrees head-down bed-rest (5 subjects) and confinement (6 subjects). We observed a significant increase (P &lt; 0.01 at D2 vs D-5) of systolic blood pressure during confinement and a different level of response for some hormones, especially for arginine vasopressin (300% increase during confinement instead of 50% during bed-rest). The renin-angiotensin-aldosterone system was enhanced during confinement and head-down bed-rest. In both conditions, we obtained a similar pattern of response for blood volume regulating hormones. During confinement, two main factors were inactivity and stress activation of the sympathetic nervous system. In the bed-rest study the response is principally due to the fluid shift and blood volume adaptation but it is not possible to exclude the role of inactivity and stress.
The effects of 28 days continuous 6 degrees head-down tilt bed-rest on heart rate variability and... more The effects of 28 days continuous 6 degrees head-down tilt bed-rest on heart rate variability and the slope of the spontaneous arterial baroreflex were evaluated during supine rest and the first 10 min of 60 degrees head-up tilt. Twelve healthy men were assigned to either a no counter-measure (No-CM), or a counter-measure (CM) group so that there was no difference in maximal oxygen uptake. Counter-measures consisted of short-term, high resistance exercise for 6 days per week from days 7-28, and lower body negative pressure (-28 mmHg) for 15 min on days 16, 18, 20 and 22-28. In spite of balanced between-group fitness, mean RR-interval was different between the No-CM and the CM group prior to bed-rest, but neither this nor any other variables showed significant counter-measure by bed-rest interaction effects. Therefore, all data presented are from the main effects of bed-rest or tilt from the analysis of variance. RR-interval was reduced significantly by bed-rest and by tilt (P < 0...
Objecti6e: The aim of the present study was to evaluate the fluid shift in a simulated microgravi... more Objecti6e: The aim of the present study was to evaluate the fluid shift in a simulated microgravity experiment and to test the use of thigh cuffs to help alleviate the problem. Methods: The change in skin thickness was assessed by a 20 MHz B-scan ultrasound device. This was performed on eight volunteers who underwent two successive 7-day periods of −6°anti-orthostatic bed-rest, with or without the daytime use of thigh cuffs. The thigh cuffs were used to counteract the development of facial oedema. Results: In the control group (without thigh cuffs), the results showed a steady increase in skin thickness of the combined dermis and hypodermis of the forehead and a reduction of the thickness of this tissue on the tibia. For the countermeasure group, although thigh cuffs were only employed during the daytime -being removed at night -their use reduced the amplitude and kinetics of the fluid shift, resulting in greater beneficial effects at the end of the day than early in the morning. Conclusion: These results of objective measurements of skin made using a non-invasive high frequency ultrasonography method confirm reports by cosmonauts of a reduction in facial oedema and a more 'comfortable' adaptation to microgravity by the use of thigh cuffs during space flight. This system is potentially promising for investigating fluid shifts in the skin and may prove useful in the evaluation of some oedematous skin diseases, as well as their therapy.
In humans, the microgravity environment can be expected to induce swelling of facial tissues and ... more In humans, the microgravity environment can be expected to induce swelling of facial tissues and shrinking of the tissues in the lower limbs, together with a loss in body weight. To evaluate fluid shifts in skin, the head-down bed-rest model was used. The aim of the present study was to evaluate the appearance of facial oedema in subjects undergoing anti-orthostatic bed-rest at an angle of -10 degrees. The forehead of each of four subjects was measured before and after 1, 10 and 24 h in this head-down tilt position. At these time points, interstitial fluid migration and facial oedema were assessed using a high resolution B-scan ultrasound and a device for measuring the skin&#39;s mechanical properties. The results obtained showed a progressive increase in dermal thickness and initial stress, and a reduction in stiffness and elasticity of the skin during the study period. This preliminary study has demonstrated the feasibility of the method in measuring fluid displacement and retention in the skin. Furthermore, it highlights the influence of fluids on the mechanical behaviour of the skin. These techniques could be used for studying the redistribution of liquid masses during periods spent in space.
Future long-duration human spaceflight will require developments to limit biocontamination of sur... more Future long-duration human spaceflight will require developments to limit biocontamination of surface habitats. The MATISS (Microbial Aerosol Tethering on Innovative Surfaces in the international Space Station) experiments allowed for exposing surface treatments in the ISS (International Space Station) using a sample-holder developed to this end. Three campaigns of FDTS (perFluoroDecylTrichloroSilane) surface exposures were performed over monthly durations during distinct periods. Tile scanning optical microscopy (×3 and ×30 magnifications) showed a relatively clean environment with a few particles on the surface (0.8 to 7 particles per mm2). The varied densities and shapes in the coarse area fraction (50–1500 µm2) indicated different sources of contamination in the long term, while the bacteriomorph shapes of the fine area fraction (0.5–15 µm2) were consistent with microbial contamination. The surface contamination rates correlate to astronauts’ occupancy rates on board. Asymmetric...
Objective: Body mass (BM) loss and body composition (BC) changes threaten astronauts' health and ... more Objective: Body mass (BM) loss and body composition (BC) changes threaten astronauts' health and mission success. However, the energetics contribution of the exercise countermeasure to these changes has never been investigated during long-term missions. We studied energy balance and BC in astronauts during 6-month missions onboard the International Space Station. Methods: Before and after at least 3 months in space, BM, BC, total and activity energy expenditure (TEE and AEE) were measured using the doubly labeled water method in 11 astronauts (2011-2017). Physical activity (PA) was assessed by the SensewearPro® activity-device. Results: Three-month spaceflight decreased BM (-1.20kg (SE 0.5); P=0.04), mainly due to non-significant fat-free mass loss (FFM;-0.94kg (0.59)). The decrease in walking time (-63.2min/day (11.5); P<0.001) from preflight was compensated by increases in non-ambulatory activities (+64.8min/day (18.8); P<0.01). Average TEE was unaffected but a large interindividual variability was noted. Astronauts were stratified into those who maintained (stable_TEE; n=6) and those who decreased (decreased_TEE n=5) TEE and AEE compared to preflight data. Although both groups lost similar BM, FFM was maintained and FM reduced in stable_TEE astronauts, while FFM decreased and FM increased in decreased_TEE astronauts (estimated between-group-difference (EGD) in ΔFFMindex [FFMI] 0.87kg/m 2 , 95%CI +0.32 to +1.41; P=0.01, ΔFMindex [FMI]-1.09kg/m 2 , 95%CI-2.06 to-0.11kg/m 2 ; P=0.03). The stable_TEE group had higher baseline FFMI, and greater baseline and inflight vigorous PA than the decreased_TEE group (P<0.05 for all). ΔFMI and ΔFFMI were respectively negatively and positively associated with both ΔTEE and ΔAEE. Conclusion: Both ground fitness and inflight overall PA are associated with spaceflight-induced TEE and BC changes and thus energy requirements. New instruments are needed to measure real-time individual changes in inflight energy balance components.
Future long-duration human spaceflight calls for developments to limit biocontamination of the su... more Future long-duration human spaceflight calls for developments to limit biocontamination of the surface habitats. The MATISS experiment tests surface treatments in the ISS’s atmosphere. Four sample holders were mounted with glass lamella with hydrophobic coatings, and exposed in the Columbus module for ~6 months. About 7800 particles were detected by tile scanning optical microscopy (×3 and ×30 magnification) indicating a relatively clean environment (a few particles per mm2), but leading to a significant coverage-rate (>2% in 20 years). Varied shapes were displayed in the coarse (50–1500 µm2) and fine (0.5–50 µm2) area fractions, consistent with scale dices (tissue or skin) and microbial cells, respectively. The 200–900 µm2 fraction of the coarse particles was systematically higher on FDTS and SiOCH than on Parylene, while the opposite was observed for the <10 µm2 fraction of the fine particles. This trend suggests two biocontamination sources and a surface deposition impacted...
Space environ ment is inherently hostile and dangerous for astronauts. Since extra-vehicu lar act... more Space environ ment is inherently hostile and dangerous for astronauts. Since extra-vehicu lar activity (EVA) should be limited or assisted as much as possible, the significant role of robot ic systems is of notable relevance. Tele-navigation of ground rovers in hostile and unknown environments is one of the applicable p roblems for modern planetary exp loration missions. Pilots involved in these missions should be supported with intelligent and adaptive Hu man-Machine Interfaces (HM Is) able to guarantee a high level of situation awareness and an affordable mental workload. This paper aims to illustrate the approach used to design, test and assess a Remote Control Station (RCS) fo r ground missions. The RCS is used to remotely operate a 4-wheel drive scaled vehicle, representing a min i-rover for space exp loration. The complete system includes the control station and the vehicle, all based on off-the-shelf components. The rover is used as a tool to assess operator"s situation awareness provided through the Graphic User Interface (GUI). This research activity is part of the project STEPSa research project co-financed by Pied mont Region.
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 1999
To clarify whether exposure to 6° head-down tilt (HDT) leads to alterations in body fluid volumes... more To clarify whether exposure to 6° head-down tilt (HDT) leads to alterations in body fluid volumes and responses to a saline load similar to those observed during space flight we investigated eight healthy subjects during a 4-day, 6° HDT and during a time-control ambulatory period with cross-over. Compared with the ambulatory period, HDT was associated with greater urinary excretion of water and sodium (UV, UNaV) from 0 to 12 h (cumulated UV 1,781 ± 154 vs. 1,383 ± 170 ml, P < 0.05; cumulated UNaV 156 ± 14 vs. 117 ± 9 mmol, P < 0.05), and with higher plasma atrial natriuretic factor (ANF) at 4 h. Hemoglobin and hematocrit increased over the first 24 h, and blood and plasma volumes were decreased after 48 h of HDT ( P< 0.05). Plasma renin activity (PRA) and aldosterone did not differ between the two groups. With prolongation of HDT, UV and UNaV returned close to baseline values. On the fourth HDT day, a 30-min infusion of 20 ml/kg isotonic saline was performed, while a large ...
American Journal of Physiology-Heart and Circulatory Physiology, 1998
Changes in autonomic nervous system activity could be linked to the orthostatic intolerance (OI) ... more Changes in autonomic nervous system activity could be linked to the orthostatic intolerance (OI) that individuals suffer after a spaceflight or head-down bed rest (HDBR). We examined this possibility by assessing the sympathetic nervous system activity during 42 days of HDBR in seven healthy men. Heart rate variability was studied with the use of power spectral analysis, which provided indicators of the sympathetic (SNSi) and parasympathetic (PNSi) nervous system influences on the heart. Urinary catecholamines and the spontaneous baroreflex sensitivity were measured. Urinary catecholamines decreased by 21.3%, showing a decrease in SNSi. Heart rate variability was greatly reduced during 42 days of HDBR with a drop in PNSi but with no significant changes in SNSi. The baroreflex sensitivity was greatly reduced (30.7%) on day 42 of HDBR. These results suggest a dissociation between the catecholamine response and the SNSi of the heart rate. This dissociation could be the consequence of a...
The effect of exercise and LBNP countermeasures on the cardiovascular deconditioning response hav... more The effect of exercise and LBNP countermeasures on the cardiovascular deconditioning response have been evaluated by the study of heart rate variability during progressive LBNP tests before, during (day 15), and after 28 d continuous 6 degrees head-down tilt bed rest. Twelve healthy men (age 27-42 years) were studied in two groups. Six were assigned to a countermeasure regime (CM) consisting of strenuous short-term resistance exercise once per day, 6 days per week from day 7 to day 28, combined with lower body negative pressure (LBNP, -28 mm Hg) for 15 min on days 16, 18, 20, and 22-28. Results were compared with data from six subjects, matched on the basis of maximum oxygen uptake, who received no countermeasures (No-CM). The main effects of bed rest were seen in reductions in RR-interval, and in total spectral power. The results of spectral analysis showed a significant reduction in an index of parasympathetic activity with a nonsignificant increase in a sympathetic indicator. The...
Cardiovascular responses to orthostatic tests were studied before and after a prolonged 42 day-he... more Cardiovascular responses to orthostatic tests were studied before and after a prolonged 42 day-headdown bed-rest (HDBR;A6°) experiment simulating a long duration space¯ight. Seven men participating in the experiment underwent stand tests (10 min) and lower body negative pressure (LBNP) tests (5 min at A25, A35, A45 mmHg). Heart rate variability and spontaneous barore¯ex response slope (SBS) were analysed to assess autonomic nervous system responses. Changes in plasma volume (PV) were assessed at the end of HDBR. At the end of HDBR, four subjects could not complete the stand tests and one could not complete the LBNP test. A higher stressed heart rate with standing (+44% before and +57% after HDBR) and LBNP exposure (+19% before and +34% after HDBR) were observed. A decrease in blood pressure (BP) re¯ecting a reduced vasomotor response was only observed with standing (mean BP +21% before and A8% after HDBR); LBNP was less sensitive probably because it was performed 6 h after the stand test. The PV decreased by 10.6%. A decline in spectrum total power re¯ecting a reduced variance of RR-interval, a decrease in parasympathetic activity and an increase in sympathetic one were observed at the end of HDBR. The reduced parasympathetic indicator and SBS would suggest that the vagal nerve component of the cardiovascular control had been diminished. Except for a lower BP when standing after HDBR, no signi®cant dierence was observed between ®nishers and non-®nishers. Autonomic nervous system changes including reduced vasomotor responses constituted important contributors to the orthostatic intolerance observed here and after space¯ights. Some autonomic and PV changes seemed to be opposite to those observed with training and would suggest a role of reduced physical activity in cardiovascular changes induced by HDBR.
Thoraco-cephalic fluid shift induced by weightlessness may influence cerebral autoregulation. Our... more Thoraco-cephalic fluid shift induced by weightlessness may influence cerebral autoregulation. Our objective was to assess effects of simulated weightlessness by a 7-day head-down bed rest (HDBR) on the kinetics of cerebral blood flow (CBF) autoregulation in eight healthy women (27.9 +/- 0.9 years). This was studied by transcranial Doppler (TCD) of the middle cerebral artery (MCA) during the sudden decrease in blood pressure (BP) induced by quickly deflating thigh cuff aftera 4-min arterial occlusion before (D - 3), during (D2, D5) and after the HDBR (D + 1). BP (Finapres) and MCA maximal blood flow velocity were continuously recorded. Cerebrovascular resistance (CR) was expressed as the ratio of mean BP to mean MCA velocity. The CR slope was defined as changes in CR per second during the BP decrease. The magnitude of the relative decrease in mean BP and MCA velocity as well as the CR slope did not differ significantly before, during and after the HDBR, showing no major impairment of cerebral autoregulation during short-term HDBR. The time to maximum decrease in CR (T1 in s), corresponding to the maximum vasodilation was reduced on D2 (7-2 +/- 0.6) versus D - 3 (9.9 +/- 1-3), D5 (9-6 +/- 0.8) and R + 1 (11.7 +/- 11) probably as a result of the fluid shift. We also looked if the responses during the thigh cuff release differed in women according to their tolerance to the 10 min stand test performed after the HDBR: T1 was larger in the five women who presented orthostatic intolerance suggesting that some differences in cerebral autoregulatory responses may be related to orthostatic intolerance.
This new multi-disciplinary medical experimentation center provides the ideal scientific, medical... more This new multi-disciplinary medical experimentation center provides the ideal scientific, medical and technical environment required for research programs and to prepare international space station Alpha (ISSA) missions, where space and healthcare industries can share their expertise. Different models are available to simulate space flight effects (bed-rest, confinement,...). This is of particular interest for research in Human psychology, physiology, physiopathology and ergonomics, validation of biomedical materials and procedures, testing of drugs, and other healthcare related products. This clinical research facility (CRF) provides valuable services in various fields of Human research requiring healthy volunteers. CRF is widely accessible to national and international, scientific, medical and industrial organisations. Furthermore, users have at their disposal the multi-disciplinary skills of MEDES staff and all MEDES partners on a single site.
The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriureti... more The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriuretic factor), electrolytes and creatinine concentrations, and blood pressure were measured in two different four-week experimental protocols: respectively -6 degrees head-down bed-rest (5 subjects) and confinement (6 subjects). We observed a significant increase (P &lt; 0.01 at D2 vs D-5) of systolic blood pressure during confinement and a different level of response for some hormones, especially for arginine vasopressin (300% increase during confinement instead of 50% during bed-rest). The renin-angiotensin-aldosterone system was enhanced during confinement and head-down bed-rest. In both conditions, we obtained a similar pattern of response for blood volume regulating hormones. During confinement, two main factors were inactivity and stress activation of the sympathetic nervous system. In the bed-rest study the response is principally due to the fluid shift and blood volume adaptation but it is not possible to exclude the role of inactivity and stress.
The effects of 28 days continuous 6 degrees head-down tilt bed-rest on heart rate variability and... more The effects of 28 days continuous 6 degrees head-down tilt bed-rest on heart rate variability and the slope of the spontaneous arterial baroreflex were evaluated during supine rest and the first 10 min of 60 degrees head-up tilt. Twelve healthy men were assigned to either a no counter-measure (No-CM), or a counter-measure (CM) group so that there was no difference in maximal oxygen uptake. Counter-measures consisted of short-term, high resistance exercise for 6 days per week from days 7-28, and lower body negative pressure (-28 mmHg) for 15 min on days 16, 18, 20 and 22-28. In spite of balanced between-group fitness, mean RR-interval was different between the No-CM and the CM group prior to bed-rest, but neither this nor any other variables showed significant counter-measure by bed-rest interaction effects. Therefore, all data presented are from the main effects of bed-rest or tilt from the analysis of variance. RR-interval was reduced significantly by bed-rest and by tilt (P < 0...
Objecti6e: The aim of the present study was to evaluate the fluid shift in a simulated microgravi... more Objecti6e: The aim of the present study was to evaluate the fluid shift in a simulated microgravity experiment and to test the use of thigh cuffs to help alleviate the problem. Methods: The change in skin thickness was assessed by a 20 MHz B-scan ultrasound device. This was performed on eight volunteers who underwent two successive 7-day periods of −6°anti-orthostatic bed-rest, with or without the daytime use of thigh cuffs. The thigh cuffs were used to counteract the development of facial oedema. Results: In the control group (without thigh cuffs), the results showed a steady increase in skin thickness of the combined dermis and hypodermis of the forehead and a reduction of the thickness of this tissue on the tibia. For the countermeasure group, although thigh cuffs were only employed during the daytime -being removed at night -their use reduced the amplitude and kinetics of the fluid shift, resulting in greater beneficial effects at the end of the day than early in the morning. Conclusion: These results of objective measurements of skin made using a non-invasive high frequency ultrasonography method confirm reports by cosmonauts of a reduction in facial oedema and a more 'comfortable' adaptation to microgravity by the use of thigh cuffs during space flight. This system is potentially promising for investigating fluid shifts in the skin and may prove useful in the evaluation of some oedematous skin diseases, as well as their therapy.
In humans, the microgravity environment can be expected to induce swelling of facial tissues and ... more In humans, the microgravity environment can be expected to induce swelling of facial tissues and shrinking of the tissues in the lower limbs, together with a loss in body weight. To evaluate fluid shifts in skin, the head-down bed-rest model was used. The aim of the present study was to evaluate the appearance of facial oedema in subjects undergoing anti-orthostatic bed-rest at an angle of -10 degrees. The forehead of each of four subjects was measured before and after 1, 10 and 24 h in this head-down tilt position. At these time points, interstitial fluid migration and facial oedema were assessed using a high resolution B-scan ultrasound and a device for measuring the skin&#39;s mechanical properties. The results obtained showed a progressive increase in dermal thickness and initial stress, and a reduction in stiffness and elasticity of the skin during the study period. This preliminary study has demonstrated the feasibility of the method in measuring fluid displacement and retention in the skin. Furthermore, it highlights the influence of fluids on the mechanical behaviour of the skin. These techniques could be used for studying the redistribution of liquid masses during periods spent in space.
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Papers by Alain Maillet