Biomedical subjects
C Boutelier
Publications and source records attributed to C Boutelier.
The stability of psychometric performance during the International Biomedical Expedition to the Antarctic (IBEA).
A selection of tests designed to measure certain cognitive and psychomotor functions was administered to 11 subjects on an Antarctic expedition, some of whom had been preacclimatized with cold baths. No evidence was found of deterioration due to the Antarctic climate, or to the lack of preacclimatization. It was concluded that the motivation of the subjects was the crucial factor in maintaining their performance.
Hormone response of normal and intermittent cold-preadapted humans to continuous cold.
This study examined the hormonal and thermal responses of two groups of subjects during 16 days in the Arctic (mean temperature -26.8 degrees C). One group (NPA) received no prior cold exposure, whereas the second group (PA) was subjected to nine daily immersions (20-40 min) in cold water (15 degrees C) 20 days before the Arctic exposure. Nude cold tolerance tests (cold air at 10 degrees C) were administered to both groups before and after the Arctic exposure. The NPA group showed an increase in metabolism and rectal temperature, whereas the PA group showed no elevation in metabolism and a decrease in rectal temperature. In the Arctic significant daily increases over the control period of urine volume (+86%), urinary norepinephrine (+48%), epinephrine (+84%), and 17-hydroxycorticosteroids (+34%) occurred in the NPA group. Only epinephrine (+65%) increased in the PA group. The hormonal and thermal responses of the NPA group in the Arctic were characteristic of metabolic adaption, whereas those in the PA group were suggestive of a hypothermic type of adaptation or habituation with no evidence of sympathetic or adrenocortical stimulation. The hormonal and thermal responses observed in this study indicate that a degree of cold resistance can be induced rapidly in humans by short intermittent exposures to an intense cold stress, which persists for a significant period of time after the last exposure.
[Comparison of the sweating rate under thermal constraint equivalent at rest and during exercise].
Subjects exposed to tolerable thermal constraints of equal intensity at rest and during exercise start sweating at lower mean body temperatures during exercise and the sweating rate increases faster during exercise than at rest.
Experimental study of convective heat transfer coefficient for the human body in water.
The steady-state convective heat transfer coefficient in water has been determined by partitional calorimetry for 17 nude subjects. Four water velocities were investigated: 0, 0.05, 0.10, and 0.25 m-s-1; and the water temperature ranged from 33.7 to 18 degrees C. In still water, hc varied from 43 W-m-2-degrees C-1 in thermoneutral conditions and a shivering rate less than 90 W-m-2 to 54 W-m-2-degrees C-1 in cold water with a shiver rate greater than 110 W-m-2. The equation, hc=0.09 (Gr-Pr)0.275, give a good approximation of this coefficient. In stirred water and for the same limits of shivering, hc can be expressed as a power function of the velocity: hc = 272.9 v0.5 and hc = 497.1 v0.65, respectively. These equations show that the flow is laminar in thermoneutral conditions and intermediate between laminar and turbulent in cold water. A study of the influence of skinfold on the magnitude of hc shows that higher values of this coefficient were obtained for thin subjects than for fat ones, concomitant with more intense shivering. The utilization of a theoretical physical model for computations of hc gave excessively high values because such methods do not embody the body shape factor and reduction of water flow adjacent to the skin.
Comparison of shivering in man exposed to cold in water and in air.
Metabolic rate (M), mean skin temperature (Tsk) and rectal temperature (Tre) were studied during 2 h exposure to cold in the air (Ta = 15-25 degrees C) and in water (TH2O = 24-32 degrees C). From the results, it was possible to draw tentative equations of the metabolic response in transient and steady state as functions of body temperatures: Mair = 41,3-57.77 dTsk/dt-5.01 (Tskt-Tsk0) and Mwater = Mair + 984.15-23.79 Tre. These equations show an important difference between the two groups of experiments: in water, both Tsk and Tre are required, whereas Tsk suffices in air. This leads to discuss the usage of mean weighted skin temperature and rectal temperature to describe peripheral and central input respectively, specially on man in cold air, in the range of these experiments.
Mathematical model of man's tolerance to cold using morphological factors.
A mathematical model has been developed to anticipate the physiological responses and the thermal state of a naked human under exposure to cold, taking into account his morphological characteristics (skinfold, size, weight) and the environmental conditions (air or water temperature and velocity, barometric pressure and hygrometry). The skinfold conditions the body's thermal conductance and the metabolism depends both on rectal (Tre) and mean skin (Tsk) temperatures. After being tested, this model was used to study the evolution of Tre. It shows the influence of the skinfold which accounts for most of the inter-individual differences. It also permits discussion of survival possibilities during immersion and completes data provided by previously established curves.
Circadian variations in the sweating mechanism.
Sweat rates and body temperatures of human subjects were measured at 0200, 1000, and 1800 h during a heat exposure of 90 min. The latent period of sweating was not significantly altered in the evening but significantly shortened during the night. Mean body temperature corresponding to the onset of sweating was nearer to the basal body temperature during the night, while during the day the difference between these two temperatures became larger. This phenomenon seems related to the circadian cycle of vasomotor adjustment, since during the night body conductance was higher than during the day and corresponded to a state of a vasodilatation similar to that observed at the onset of sweating. During the day, this situation was reversed. During steady state, the following changes were observed: sweating rate, night less than morning less than evening; skin temperatures, night less than morning less than evening; and rectal temperature increase, morning less than evening less than night. It is hypothesized that these changes are due to either different metabolic rates or an imbalance between heat gains and losses which preserve the circadian rhythm of the body temperature, even under thermal loads.
[A model of sweating during muscular exercise].
From a practical viewpoint, thermal sweating during exercise can be described by an exponential equation. The errors from this mathematical model are of few importance. Nevertheless, metrologic and physiological factors can complicate theoretically the model.
[Relation between ventilation and oxygen consumption during thermal shiver in man].
Explore the source record for details and available documents.
[The place of perspiration and sweating in the nycthermal control of body temperature].
Explore the source record for details and available documents.
[Thermal conductance of the human body during immersion in thermally neutral and in cold water].
Explore the source record for details and available documents.
[Performances during heat in supersonic aircraft].
Explore the source record for details and available documents.
[Thermal balance in man during 24 h in controlled environment].
Explore the source record for details and available documents.
Skin temperatures in warm environments and the control of sweat evaporation.
Explore the source record for details and available documents.
[Circadian evolution of skin temperatures in humans at rest in neutral temperature conditions].
Explore the source record for details and available documents.
[Role of the subcutaneous adiposus panniculus in transient thermic phenomena during immersions in cold water].
Explore the source record for details and available documents.
[Calorimetric interpretation of the circadian thermal rhythm in man].
Explore the source record for details and available documents.