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Biomedical subjects

P Varène

Publications and source records attributed to P Varène.

At least 19 recordsLinked to original sources
PubMed1989

Effects of water temperature on pulmonary volumes in immersed human subjects.

Pulmonary volumes and capacities have been measured at three water temperatures (Tw = 25, 34, 40 degrees C) in standing subjects immersed up to the shoulders. The comparison of data obtained in air with those obtained in thermoneutral immersion (Tw = 34 degrees C) confirms the results previously published in several studies. The comparison of data obtained in immersion at different Tw shows: 1. A significant decrease in vital capacity (VC) with bath temperature (VC 40 degrees C greater than VC 34 degrees C greater than VC 25 degrees C). The same decrease is observed in the inspiratory reserve volume (IRV) while the expiratory reserve volume (ERV), the residual volume (RV) and the functional residual capacity (FRC) do not vary. 2. A significant decrease in maximum breathing capacity (MBC) with bath temperature (MBC 40 degrees C greater than MBC 25 degrees C). 3. A significant increase in tidal volume (VT) in cold or hot water compared to thermoneutral water (VT40 degrees C greater than VT34 degrees C; VT34 degrees C less than VT25 degrees C) during quiet breathing. Breathing frequency does not change, thus ventilation (V) follows the same evolution as VT. The relative abdominal (ABD) contribution to VT, estimated by a double belt inductance plethysmograph, is reduced at Tw = 25 degrees C but unchanged at Tw = 40 degrees C compared to thermoneutral bath. Beside variations in the metabolic state, the variations of the pulmonary volumes as a function of Tw are estimated to be mainly due to alterations in respiratory muscles functioning.

Adult↗
PubMed1986

Heat and water respiratory exchanges: comparison between mouth and nose breathing in humans.

The temperatures (TI, TE) of inspired and expired gas and the mass of expired water (MEH2O) have been measured in four subjects at rest during mouth and nose breathing of dry air at room temperature. TI and TE were measured by copper-constantan thermocouples, MEH2O by freezing and ventilatory parameters by total body plethysmography. During mouth breathing, temperatures are significantly higher (TI = 28.1 degrees C, TE = 31.5 degrees C) and the amount of expired water larger (MEH2O = 27.8 mg dm-3 BTPS) than during nose breathing (TI = 24.8 degrees C; TE = 29.6 degrees C; MEH2O = 26.6 mg dm-3 BTPS). From these experimental data the appropriate computations show clearly that in humans, while either nose or mouth breathing, the expired air is not water saturated; the latent heat exchanges represent the larger part of the respiratory heat exchanges; the counter current expiratory heat recovery is imperfect; in terms of heat and water respiratory exchanges, no large difference exists between the oral and nasal routes. This last point is confirmed by the calculation of a difference less than 10% in the total respiratory heat losses between mouth and nose breathing.

Body Temperature Regulation↗
PubMed1984

Respiratory water loss as a function of ventilatory or environmental factors.

Since expired gas is not water-saturated (Ferrus et al., 1980, Respir. Physiol. 39: 367-381), its water content should depend on biological or environmental factors other than expired gas temperature. In order to verify this hypothesis, multiple linear regression relationships between MEH2O, the mass of water expired per litre of BTPS ventilated gas and respiratory frequency (f) or period (TR), tidal volume (VT), ventilation (V), temperature of inspired gas (TI), density of inspired gas mixture (rho I), partial pressure of water in inspired gas (PIH2O) were computed from 345 experiments performed on 7 subjects. This analysis shows that MEH2O is positively and significantly correlated to TI (0.22 mg . dm-3 . degrees C-1), to PIH2O (0.14 mg . dm-3 . Torr-1), and to TR (0.87 mg . dm3 . s-1). MEH2O is negatively and significantly correlated to f (-0.27 mg . dm-3(cy . min-1)-1) to rho I (-0.06 mg . dm-3(g . dm-3)-1) and to V (-0.09 mg . dm-3(dm3 . min-1)-1). There is no statistical correlation between MEH2O and VT. It is concluded that the respiratory water loss depends to a large degree on respiratory or environmental conditions. This dependence supports the previously published results suggesting that expired gas is not water saturated.

Environment↗