Biomedical subjects

G Savourey

Publications and source records attributed to G Savourey.

At least 37 records · Page 2Linked to original sources

PubMed1997

Effects of various beverages on the hormones involved in energy metabolism during exercise in the heat in previously dehydrated subjects.

The objective of our study was to examine the effects of beverage content on hormone responses involved in fuel substrate metabolism (catecholamines, insulin and glucagon) in previously dehydrated subjects exercising at a moderate intensity in the heat. Six healthy men walked for 60-min on five occasions at 50% maximal oxygen uptake in a warm environment (dry bulb temperature 35 +/- 0.2 degrees C, relative humidity 20%). On each occasion, the subjects were dehydrated before exercise (loss of 2% body mass) by passive controlled hyperthermia, which led to a reduction in plasma volume (PV) of about -5% to -9%. In one session, the subjects exercised without rehydration (Dh). In the other sessions, four beverages (650 ml) were given just before the exercise: mineral water (W), a 60 g x l(-1) glucose and 1.2 g x l(-1) NaCl solution (GS), a 60 g x l(-1) maltodextrin solution, and a 60 g x l(-1) maltodextrin and 1.2 g x l(-1) NaCl solution. Compared to Dh and W, carbohydrate supply with or without NaCl induced a higher glycaemia (P < 0.05), a reduced increase in plasma adrenaline concentration (P < 0.05) and a higher plasma insulin concentration (P < 0.05), which lowered plasma free fatty acids and glycerol concentrations (P < 0.05). The lesser increase in plasma noradrenaline concentrations observed during GS compared to Dh and W sessions can be explained by a larger correction in PV which might have induced better haemodynamic conditions. However, the increase in plasma glucagon with carbohydrate supply--compared to Dh and W (P < 0.05)--remains unexplained.

Adult↗

PubMed1997

Are the laboratory and field conditions observations of acute mountain sickness related?

In order to study relationships between acute mountain sickness (AMS) observations done both during a short-term hypoxic exposure in a hypobaric chamber, and in field conditions during a high altitude expedition, nine subjects were submitted to a 9-h hypoxic exposure in a hypobaric chamber. Then, they experienced a high altitude expedition in the Himalayas. The Lake Louise AMS scoring system was used to assess AMS in both conditions, especially the self report questionnaire. During the expedition, the mean self report score of each subject, defined as the ratio between the sum of daily self report scores and the duration of the expedition, appears to be correlated not only to the maximal self report score observed in altitude (r = +0.77, p < 0.05) but also to the self report and self report+clinical assessment scores observed at the end of the hypobaric chamber sojourn (r = +0.81, p < 0.01 and r = +0.75, p < 0.05, respectively). In conclusion, the Lake Louise AMS scoring system, especially the self report questionnaire, is relevant to assess AMS with simplicity and rapidity both in laboratory and in field conditions. Our study also suggests that AMS induced by a short term sojourn in a hypobaric chamber is related to AMS observed in field conditions.

Acute Disease↗

PubMed1997

Cognitive performance during short acclimation to severe hypoxia.

BACKGROUND: Exposure to high altitudes requires acclimation or acclimatization, to prevent the negative effects of severe hypoxia. Among several methods, short acclimation with intermittent exposure to severe hypoxia in a hypobaric chamber triggers efficient physiological pre-adaptation mechanisms (11-13). However, we have little knowledge about the cognitive repercussions of such an acclimation protocol. METHODS: Four mountaineers were tested daily in the course of a short acclimation protocol (5 d). After their SaO2 (arterial oxyhemoglogin saturation) were recorded, they carried out a choice reaction time task (Manikin test) twice every day; first at ground level (250 m, control sessions), second at the highest altitude of the day (D1 = 5000 m, D2 = 5500 m, D3 = 6000 m, D4 = 6500 m, D5 = 7000 m). RESULTS: High altitude SaO2 level decreased during the first 3 d, then stabilized around 72-73%. Despite a slight and transient increase at the highest altitude relative to the ground level in D4, the error rate remained low throughout the protocol. Further, response time to the Manikin task did not show significant changes among the days during the acute stage of hypoxia relative to ground level up to 7000 m. CONCLUSIONS: On the whole, it seems that a short acclimation protocol based on intermittent exposure to simulated high altitudes triggered adaptive processes without major impairment in a choice reaction time task during the acute stages of severe hypoxia.

Acclimatization↗

PubMed1997

[Travelers exposed to extreme temperatures].

Sudden introduction of the unadapted human into extreme environments can result in serious, sometimes fatal, reactions. Most complications are due either to failure of thermoregulatory system or consecutive to the physiological responses to those environmental conditions. In addition to a number of minor diseases, cold can cause two major accidents, i.e., hypothermia and frostbite which can be enhanced at altitude. Moreover, the main disease in altitude conditions is represented by the acute mountain sickness which can lead to acute pulmonary and cerebral edema. Heat can cause heatstroke, dehydration, syncope, and other minor disorders. Prevention of these manifestations during stays in inhospitable climatic conditions for which the body is not suited requires knowledge of the environment and its dangers. Implementation of suitable measures can greatly reduces the incidence of adverse effects.

Adaptation, Physiological↗

PubMed1996

Pre-adaptation, adaptation and de-adaptation to high altitude in humans: cardio-ventilatory and haematological changes.

The aim of this study was first to investigate cardio-ventilatory and haematological responses induced by intermittent acclimation and second to study de-adaptation from high altitude observed after descent. To achieve these objectives nine subjects were submitted to intermittent acclimation in a low barometric chamber (8 h daily for 5 days, day 1 at 4500 m, day 5 at 8500 m) before an expedition to the Himalayas. Cardio-ventilatory changes were measured during a hypobaric poikilocapnic hypoxic test (4500 m, barometric pressure = 589 hPa) and haematological changes were studied at sea level. These measurements were performed before and after acclimation, after return to sea level, but also 1 and 2 months after the expedition. In addition, partial pressures of oxygen and carbon dioxide in arterial blood (PaO2, PaCO2) and arterial erythropoietin concentration [EPO] were measured at rest during the hypoxic test. Results suggested the pre-adaptation protocol was efficient since an increased PaO2 (+12%, P < 0.05), a smaller difference in alveolo-arterial PO2 ( -63%, P < 0.05) and a lower PaCO2 ( -11%, P < 0.05), subsequent to ventilatory changes, were observed after acclimation with a significant increase in reticulocytes and in sea level [EPO] (+44% and +62% respectively, P < 0.05). De-adaptation was characterized by a loss of these cardio-ventilatory changes 1 month after descent, whereas the haematological changes (increased red blood cells and packed cell volume, P < 0.05) persisted for 1 month before disappearing 2 months after descent. This study would also suggest that acute hypoxia performed after a sojourn at high altitude could induce significantly depressed EPO responses (P < 0.05).

Adaptation, Physiological↗

PubMed1996

Biometrical characteristics and physiological responses to a local cold exposure of the extremities.

The aim of this study was firstly to describe the physiological responses observed in 19 subjects during immersion of the arm up to the elbow in water at 5 degrees C (5 min) followed by a 10-min recovery and secondly, to correlate the observed physiological responses with biometrical characteristics of the subjects (maximal oxygen uptake, VO2max, percentage fat content of whole body, BF, and arm, forearm and hand skinfold thickness). The results showed that the time courses of changes in forearm and hand skin temperature were different compared to those of finger skin temperatures both during local cooling and during rewarming (P < 0.05). Cardiovascular responses (heart rate, systolic and diastolic blood pressures) and finger skin temperatures were not related to the biometrical characteristics of the subjects. However, at the end of the immersion, decreased hand skin temperature was correlated to VO2max (r = 0.45, P < or = 0.05) whereas decreased forearm skin temperature was correlated both to VO2max (r = 0.44, P < or = 0.05) and to skinfold thickness (r = -0.44, P < or = 0.05) but not to BF. During the beginning of the recovery period only, outside, inside forearm and hand skin temperatures were related to VO2max (r = 0.54, P < or = 0.05; r = 0.66, P < or = 0.01 and r = 0.45, P < or = 0.05, respectively) and all the skinfold thicknesses (r = -0.47 to -0.71, P < or = 0.05). It was concluded that the local skin temperature profiles differed according to the upper limb segment both during cooling and during early rewarming. Moreover, VO2max and upper limb skinfold thickness but not BF did influence the forearm and hand skin temperature changes during cooling and early rewarming but not the finger skin temperature changes and cardiovascular responses.

Adult↗

PubMed1996

Hypothermic general cold adaptation induced by local cold acclimation.

To study relationships between local cold adaptation of the lower limbs and general cold adaptation, eight subjects were submitted both to a cold foot test (CFT, 5 degrees C water immersion, 5 min) and to a whole-body standard cold air test (SCAT, 1 degree C, 2 h, nude at rest) before and after a local cold acclimation (LCA) of the lower limbs effected by repeated cold water immersions. The LCA induced a local cold adaptation confirmed by higher skin temperatures of the lower limbs during CFT and a hypothermic insulative general cold adaptation (decreased rectal temperature and mean skin temperature P < 0.05) without a change either in metabolic heat production or in lower limb skin temperatures during SCAT after LCA. It was concluded that local cold adaptation was related to the habituation process confirmed by decreased plasma concentrations of noradrenaline (NA) during LCA (P < 0.05). However, the hypothermic insulative general cold adaptation was unrelated either to local cold adaptation or to the habituation process, because an increased NA during SCAT after LCA (P < 0.05) was observed but was rather related to a "T3 polar syndrome" occurring during LCA.

Acclimatization↗

PubMed1995

Acute mountain sickness relates to sea-level partial pressure of oxygen.

The aim of this study was to clarify the relationships between acute mountain sickness (AMS), studied during an expedition in the Andes, and some physiological parameters determined before the expedition, i.e. biometrical characteristics of the subjects [maximal oxygen consumption (VO2max), body fat content, body mass index], functional pulmonary tests (forced vital capacity, forced expiratory volume at the first second), ventilatory or cardiac responses measured at 4,500 m [hypoxic ventilatory responses (HVR) 4,500 and hypoxic cardiac responses (HCR) 4,500, respectively), cold pressor responses. To achieve this objective, 11 subjects were firstly submitted to a hypobaric poïkilocapnic hypoxic test (589 hPa, 4,500 m) at rest and during exercise to study minute volume, respiratory frequency, end tidal partial pressure of O2 (PETO2) and CO2, HVR 4,500, HCR 4,500 and to a cold pressor test of the hand (5 min in 5 degrees C cold water) to study heart rate, blood pressure and skin temperature changes. The AMS was assessed daily by questionnaire during a 12-day expedition in the Andes following both Hackett's method and Environmental Symptoms Questionnaire (modified ESQ II). Maximal AMS-Hackett score, maximal AMS-ESQ score and mean AMS-ESQ score were defined. The quantifications of AMS following the two methods were correlated. No significant relationships were observed between mean AMS-ESQ score and the biometrical characteristics of the subjects, the functional pulmonary tests, HVR 4,500, HCR 4,500 or the cold pressor responses. However, it appeared that the mean AMS-ESQ score was correlated with PETO2 measured at rest and during exercise (50% VO2max) both in hypoxia and normoxia. A closer linear relationship was observed during the exercise in normoxia (r = -0.92, P < 0.0001). These results could suggest that AMS was related to a relative alveolar hypoventilation more in relation to breathing pattern than HVR.

Acute Disease↗

PubMed1995

Influence of hyperthermia on cochlear micromechanical properties in humans.

We investigated the effect of body temperature on transient evoked otoacoustic emissions (TEOAEs) in humans. Hyperthermic conditions were obtained in adults in a climatic chamber. During hyperthermia up to an average temperature of 38.4 degrees C, significant falls were found in total amplitude and peak values of TEOAEs: by 1.3 dB SPL/degree C and 2.3 dB/degree C, respectively. This inhibition affected all spectrum components equally. These findings indicate that the outer hair cell micromechanical activity that is presumed to be measured by TEOAEs is not independent of variations in body temperature. The reduction found in hyperthermia suggests that temperature-dependent mechanisms are involved in the generation of TEOAEs.

Adult↗

PubMed1995

Evaluation of the Lake Louise acute mountain sickness scoring system in a hypobaric chamber.

This study evaluated the relevance of the Lake Louise acute mountain sickness (AMS) scoring system in comparison with other AMS scoring systems. To achieve this objective nine subjects were submitted to a 9-hr exposure to hypoxia in a hypobaric chamber (altitude 4500-5500 m) that led to the development of AMS. AMS was scored at the end of this exposure period both by questionnaires (Hackett AMS questionnaire, Lake Louise AMS self-report questionnaire, Environmental Symptoms Questionnaire ESQ II and ESQ IV) and by a clinical investigation following the Lake Louise AMS clinical and functional AMS assessment. The AMS scores were between 0 and 9 for the Hackett AMS score, 0 and 38 for the ESQ II AMS score, 0 and 13.7 for the ESQ IV AMS score, 0 and 10 for the Lake Louise AMS self-report, 0 and 2 for the Lake Louise AMS clinical assessment score, and between 0 and 2 for the Lake Louise functional score. All the AMS questionnaire scores were related to the clinical AMS assessment score (p < 0.05) without significant differences between them. The Lake Louise AMS self-report score appeared highly correlated to other AMS scoring systems (Hackett, ESQ II and ESQ IV) (p < 0.05). Suggestions were proposed to improve the sensitivity and the specificity of the Lake Louise AMS scoring questionnaire but also the Lake Louise AMS clinical assessment. In conclusion, this study suggests the relevance of the Lake Louise AMS self-report questionnaire to assess and score AMS with simplicity and rapidity.

Adult↗

PubMed1994

Effect of ingestion pattern on rehydration and exercise performance subsequent to passive dehydration.

Six male volunteers performed three tests, each comprising a passive heating session to obtain dehydration (loss of 2.6% body mass), followed by exercise on a treadmill until exhaustion (50% of maximal oxygen consumption) in a warm environment (dry bulb temperature 35 degrees C, relative humidity 20%-30%). In one test, the subjects exercised without rehydration (Dh). In the two other tests, 50% of the fluid lost in the dehydration session was replaced by drinking mineral water given either in one amount [913 (SEM 23) ml] before the exercise (Rh1) or divided into four equal portions [228 (SEM 5) ml] before the exercise and on three occasions at 15-min intervals during exercise (Rh4). Rehydration increased exercise duration in Rh1 compared to Dh [112 (SEM 7) min and 82 (SEM 3) min, respectively; P < 0.05]. The difference was not significant with Rh4 [103 (SEM 9) min]. A restoration of the time course of changes in plasma volume, plasma osmolality, heart rate and rectal temperature occurred immediately in Rh1 and as delayed in Rh4 until after 60 min of exercise. Our results demonstrated that the swift replacement of the fluid loss in the dehydrated subjects was beneficial to exercise performance by rapidly correcting the disturbances in body fluid balance.

Adult↗

PubMed1994

Cold thermoregulatory changes induced by sleep deprivation in men.

The aim of this study was to evaluate the thermoregulatory changes induced by 27-h of sleep deprivation (SD) in men at rest both in a comfortable ambient temperature and in cold air. A group of 12 male subjects were placed in a comfortable ambient temperature (dry bulb temperature, Tdb = 25 degrees C, relative humidity, rh = 40%-50%, clothing insulation = 1 clo) for 1 h and then they were submitted to a standard cold air test in a climatic chamber for 2 h (Tdb = 1 degree C, rh = 40%-50%, wind speed = 0.8 m.s-1, nude), before and after 27 h of sleep deprivation. Thermoregulatory changes (rectal temperature, Tre; mean skin temperature. Tsk; metabolic heat production M) were monitored continuously. At comfortable ambient temperature, no significant change was observed after SD for Tre, Tsk and M. During the cold test, Tre did not change but Tsk and M were higher after SD (P < 0.05). Increased M (+ 6%, P < 0.05) was related to earlier and higher shivering, with a possible increase in the sensitivity of the thermoregulatory system as shown by the shorter time to onset of continuous shivering (d): 8.66 (SEM 1.33) min versus 28.20 (SEM 1.33) min (P < 0.001) and by a higher Tsk observed at d: 27.60 (SEM 1.40) degrees C versus 21.40 (SEM 0.60) degrees C (P < 0.001). These results were associated with higher cold sensations and shivering following SD. They also suggested that SD modified thermoregulatory responses at a central level especially in a cold environment.

Adult↗

PubMed1994

Physiological changes induced by pre-adaptation to high altitude.

To study the physiological effects of pre-adaptation to high altitude, seven subjects were submitted to acclimatization at 4350 m followed by intermittent acclimation in a low barometric pressure chamber (5000 m to 8500 m). The subjects then spent 25 days in the Himalayas. Ventilatory and cardiac responses were studied during a hypobaric poikilocapnic hypoxic test performed both at rest and during exercise (100 W) in normoxia and in hypoxia (barometric pressure: 589 hPa, altitude: 4500 m). Haemoglobin, erythrocytes, reticulocytes, packed cell volume, 2,3-diphosphoglycerate (2,3-DPG) and erythropoietin (EPO) were measured. All variables were studied before pre-adaptation to high altitude (A), after the acclimatization period (B), after the acclimation period (C) and after the expedition (D). The ventilatory and cardiac responses were characterized by an increased tidal volume in hypoxia (+33% during exercise in B, P < 0.05; +100% at rest and +33% during exercise in C, P < 0.05) without any change in respiratory frequency, whereas an increased systolic blood pressure was only observed in C during exercise in hypoxia [+23 mmHg (3.07 kPa), P < 0.01]. Arterial O2 saturation was higher in hypoxia in C and D, both at rest (+8.2% and +4.7%, P < 0.01, respectively), and during exercise (+6.3% and +6.3%, P < 0.01, respectively). Erythrocytes, haemoglobin and packed cell volume did not vary significantly. The number of reticulocytes was higher in B (+172%, P < 0.05) and in C (+249%, P < 0.05). EPO and 2,3-DPG increased only in C (+770%, P < 0.01 and +23%, P < 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗

PubMed1994

Thyroid hormone changes in a cold air environment after local cold acclimation.

Serum thyroid hormones (TH) and internal temperatures were investigated in 8 euthyroid men during a general standard cold air test (SCAT) (dry bulb temperature = 1 degree C, 2 h, nude, at rest) performed both before and after a local cold acclimation. Serum total thyroxin (TT4), total triiodothyronine (TT3), free thyroxin (FT4), free triiodothyronine (FT3), and thyrotropin (TSH) were studied during the SCT. The TH values were corrected following the plasmatic volume reduction (delta PV) calculated with Dill and Costill's formula. During SCAT, delta PV reached -9 to -11% (P < 0.05) without any effect of local cold acclimation. Slight TH changes were observed according to delta PV: TT4, TT3, and TSH increased during SCAT (P < 0.05) only before correction. FT4 and FT3 did not vary before correction but increased after correction (P < 0.05). After acclimation, a slightly decreased TT3 was observed both before and after correction (-18% and -11.7%, respectively; P < 0.05). Decreased internal temperatures after local cold acclimation suggested a hypothermic general cold adaptation. It was concluded that TH changes during SCAT differed if correction due to delta PV was applied and that the slight decrease in TT3 observed after local cold acclimation could suggest the presence of a "T3 polar syndrome."

Acclimatization↗

PubMed1993

[Induction of a "triiodothyronine polar syndrome" in man under laboratory conditions].

To precise the thyroid hormonal changes (TH) during an acute cold exposure, 8 subjects were subjected to a cold air test (2 h, 1 degrees C nude, at rest) in a climatic chamber before and after a local cold acclimation. After cold acclimation the thyroid hormonal changes could suggest the presence of a "T3 polar syndrome" in laboratory conditions. This syndrome was up to now described only after a stay in natural cold environment.

Acclimatization↗

PubMed1992

Reversal of cold induced haemoconcentration.

Classically, cold induced plasma volume reduction is explained by an increased diuresis which is generated by an inhibition of antidiuretic hormone release. However, most of the haemoconcentration appears to be reversible during rewarming. This observation weakens the former statement. The aim of this study was to clarify the mechanisms involved in the reversal of the cold induced haemoconcentration. Six young males, resting in a dorsal reclining position, were exposed successively to a thermoneutral environment (30 min), a cold environment (1 degrees C; cold) or thermoneutrality (control) for 120 min, and during a 60-min recovery period in thermoneutral conditions. During cold stress, a reduction of 15% (i.e. 510 ml) of the plasma volume was observed, and osmolality was unchanged. After the 60-min recovery under thermoneutral conditions, plasma volume variation between the Cold and the Control experiments was reduced and reached 3% (i.e. 100 ml). This volume equalled the increased amount of urine production observed during the cold stress experiment. Haemoconcentration cannot be explained by increased urinary water loss (+/- 100 ml) alone. Therefore a transient shift of plasma water from vascular to interstitial spaces, due to an increase of blood pressure, could be involved in the reduction of plasma volume.

Adult↗

PubMed1992

How should body heat storage be determined in humans: by thermometry or calorimetry?

The aim of this study was to determine whether in humans there are differences in the heat storage calculated by partitional calorimetry (S, the balance of heat gains and heat losses) compared to the heat storage obtained by conventional methods (thermometry) via either core temperature or mean body temperatures (Tb = 0.8Tc + 0.2Tsk, where Tc is core temperature and Tsk is mean skin temperature) when two different sites are used as an index of Tc [rectal (T(re)) and auditory canal (T(ac)) temperatures]. Since women respond to the heat differently than men, both sexes were studied. After a stabilisation period at thermal neutrality, six men and seven women were exposed to a globe temperature of 50 degrees C, relative humidity of 17% and wind speed of 0.8-1.0 m.s-1 for 90 min semi-nude at rest, where T(re), T(ac), Tsk, metabolic rate, dry (radiant + convective heat exchange) and evaporative heat losses, S, heat storage by Tc (STc) and heat storage by Tb (STb) were assessed every minute. In the mean, S was equal to 350.8(SEM 49.6) kJ whereas STc amounted to only 114.6(SEM 16.2) and 196.7(SEM 32.3) kJ for T(re) and T(ac), respectively (P less than 0.05). Final STb(re) underestimated S by 49% [177.7(SEM 23.0) kJ; P less than 0.05] whereas STb(ac) was not significantly different than S [255.7(SEM 37.9) kJ]. In the women, S corresponded to a total of 294.3(SEM 23.2) kJ, a value that was very similar to the STb(ac) [262.6(SEM 31.0) kJ], whereas STb(re) under-predicated S by 35% [190.4(SEM 26.3) kJ; P less than 0.05].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

General and local cold adaptation after a ski journey in a severe arctic environment.

It is hypothesized that some of the variability in the conclusions of several human cold adaptation studies could be explained if not only were the changes in core and shell temperatures taken into account, before and after cold adaptation, but also the absolute temperatures and metabolic rate in both thermally neutral environments and in the cold. Such an approach was used in a group of volunteers before and after a ski journey (3 weeks at -20 to -30 degrees C) across Greenland. Eight subjects were submitted to cold tests (Tdb = 1 degree C, r.h. = 40%, wind speed = 0.8 m.s-1) for 2 hours. Thermoregulatory changes were also monitored in a neutral environment (Tdb = 30 degrees C). In the neutral environment, the arctic journey increased metabolic rate (11.2%; P less than 0.05) and mean skin temperature [Tsk: 33.5 (SEM 0.2) degrees C vs 32.9 (SEM 0.2) degrees C, P less than 0.05]. During the cold test, the arctic journey was associated with a lower final rectal temperature [36.8 (SEM 0.2) degrees C vs 37.3 (SEM 0.2) degrees C, P less than 0.01], a lower final Tsk [20.7 (SEM 0.4) degrees C vs 21.2 (SEM 0.3) degrees C, P less than 0.01] with no change in metabolic heat production. These observations are indicative of an hypothermic insulative isometabolic general cold adaptation, which was associated with a local cold adaptation of the extremities, as shown by warmer foot temperatures [12.3 (SEM 0.9) degrees C vs 9.8 (SEM 0.9) degrees C, P less than 0.001].

Adaptation, Physiological↗