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Biomedical subjects

R R Gonzalez

Publications and source records attributed to R R Gonzalez.

At least 73 records · Page 4Linked to original sources
PubMed1984

Effects of sleep deprivation on thermoregulation during exercise.

Five fit men completed a practice, control, and sleep deprivation exercise test. Two nights of normal sleep preceded the control test, and 33 h of wakefulness preceded the sleep deprivation test. These tests consisted of 20 min of rest followed by 40 min of cycle-ergometer exercise (50% of peak O2 uptake, VO2) in a temperate (ambient temperature, 28 degrees C; relative humidity, 30%)-environment. Esophageal temperature (Tes), local sweat rate (mds), and chest thermal conductance (kch) were continuously measured. During exercise a 0.7 and 0.5 degrees C rise in Tes was found for the sleep deprivation and control tests, respectively. This increase in Tes values from rest to the end of exercise was greater (P = 0.08) for the sleep deprivation than control test. Total body sweat rate, calculated from Potter balance measurements, was 27% less (P less than 0.01) for the sleep deprivation than the control test. Both mds and kch values were lower (P less than 0.05) during the final 20 min of exercise for the sleep deprivation than control test. Final exercise mds values were 19% lower (P less than 0.05) for the sleep deprivation than control test. An asynchronous rather than a normal synchronous mds pattern was frequently observed during the sleep deprivation test. During the sleep deprivation test, the mds sensitivity (delta mds X delta Tes-1) was 38% lower (P less than 0.01) and kch sensitivity (delta kch X delta Tes-1) was 42% lower (P less than 0.05) than during the control test. These data indicate that sleep deprivation decreases evaporative and dry heat loss during moderate-intensity exercise.

Adolescent↗
PubMed1984

Tissue pressure and plasma oncotic pressure during exercise.

Six healthy male subjects exercised on a cycle ergometer for 3 min for assessment of forces involved in transvascular fluid shift during intense exercise. The work load was at 105% of peak O2 uptake of the subjects. This caused a 17.2 +/- 1.2% reduction in plasma volume. The plasma volume loss was associated with an increase in plasma sodium, from 142.6 +/- 0.5 to 148.1 +/- 1.0 meq X 1(-1) (P less than 0.005); chloride, from 101.8 +/- 0.6 to 104.6 +/- 0.9 meq X 1(-1) (P less than 0.005); lactate, from 1.4 +/- 0.2 to 14.0 +/- 1.5 meq X 1(-1) (P less than 0.005); and osmolality, from 283 +/- 2 to 299 +/- 3 mosmol X kg-1 H2O (P less than 0.005) within 2 min after cessation of exercise. Plasma protein increased from 7.0 +/- 0.2 to 8.1 +/- 0.3 g X dl-1 (P less than 0.005), and plasma colloid osmotic pressure from 25.1 +/- 0.6 to 30.6 +/- 1.4 mmHg (P less than 0.005) after exercise. Interstitial fluid pressure in the exercising vastus lateralis muscle increased from a base-line value (SE) of -1.0 +/- 0.9 to + 1.5 +/- 1.1 cmH2O, 14 min after the end of exercise (P less than 0.05). Interstitial fluid pressure of the triceps brachii (inactive) did not change significantly after exercise. Our data suggest that increased transvascular colloid osmotic pressure and elevation of interstitial fluid pressure become increasingly important in preventing loss of plasma volume during maximal exercise.

Adult↗
PubMed1984

Heat exchange following atropine injection before and after heat acclimation.

The effect of saline and atropine injection (2 mg, im) on eight healthy male subjects before and after heat acclimation was studied while each subject walked on a treadmill (1.34 m X s-1) in a hot-dry environment (ambient temperature = 48.4 degrees C, dew-point temperature = 20.5 degrees C). Partitional calorimetric analysis was done for the periods in which maximum sweat inhibition occurred (30 min). Mean skin temperature, rectal temperature, and heart rate were continuously observed. Evaporative loss from the skin was calculated by changes in body weight (Sauter balance); heat transfer coefficients were defined by Nishi equations. A prediction of sweat inhibition based on an analysis of heat storage and its effect on a theoretical temperature, which can be graphed on a psychrometric chart, was developed. A rational effective temperature (ET) defined as the operative temperature at the intersection of the 50% rh, which encompasses total heat exchange, was used to compare the effects of atropine before and after heat acclimation. The results show that heat acclimation reduced ET by approximately 2.5 degrees C when compared with the unacclimated state after atropine injection. Thus heat acclimation reduces the hazards of heatstroke caused by exercise in the heat with atropine injection.

Acclimatization↗
PubMed1984

Heat exchange during upper- and lower-body exercise.

This study examined evaporative and dry heat exchange during upper- and lower-body exercise. Four male subjects performed arm-crank or cycle exercise at the same O2 uptake level (approximately 1.6 l/min) in an environment facilitating dry heat exchange [radiative and convective (R + C)] [ambient temperature (Ta) = 18 degrees C, dew-point temperature (Tdp) = 14 degrees C] and an environment facilitating evaporative heat loss (Esk) (Ta = 35 degrees C, Tdp = 14 degrees C). (R + C) was determined from the torso with a net radiometer and from the limbs with heat flow discs, whereas Esk was determined from the torso and limbs by ventilated dew-point sensors. In both environments neither esophageal temperature nor mean skin temperature were different between exercise types (P greater than 0.05). Torso (R + C) was significantly (P less than 0.05) greater during arm-crank than during cycle exercise in both environments. Torso Esk, as well as arm (R + C), and arm Esk were not different (P greater than 0.05) between exercise types in each environment. Leg (R + C) was greater (P less than 0.05) during cycle than during arm-crank exercise in the 18 degrees C environment, whereas leg Esk was greater (P less than 0.05) during cycle than during arm-crank exercise in the 35 degrees C environment. These data indicate that to compensate for greater torso sensible heat loss during upper body exercise lower body exercise elicits additional (R + C) or Esk from the legs. The avenue for this compensatory sensible and insensible heat loss depends upon the differential heat transfer coefficients which influence tissue conductivity and mass transfer.

Adult↗
PubMed1983

Spectral analysis of Doppler ultrasonic flow signals by a personal computer.

This paper describes a method of performing spectral analysis on Doppler acoustical signals from peripheral blood vessels with the use of an Apple II plus personal computer. Digitization is accomplished with a commercially available analog-to-digital converter. The data are transformed with a fast Fourier technique, and the resultant information is plotted by an inexpensive X-Y plotter and/or on a television receiver.

Blood Vessels↗
PubMed1982

Automatic dew-point temperature sensor.

A device is described for measuring dew-point temperature and water vapor pressure in small confined areas. The method is based on the deposition of water on a cooled surface when at dew-point temperature. A small Peltier module lowers the temperature of two electrically conductive plates. At dew point the insulating gap separating the plates becomes conductive as water vapor condenses. Sensors based on this principle can be made small and rugged and can be used for measuring directly the local water vapor pressure. They may be installed within a conventional ventilated sweat capsule used for measuring water vapor loss from the skin surface. A novel application is the measurement of the water vapor pressure gradients across layers of clothing worn by an exercising subject.

Body Surface Area↗
PubMed1978

Indices of thermoregulatory strain for moderate exercise in the heat.

The effect of varying humidity and dry bulb temperatures was studied on five normal male unclothed subjects while exercising (40-45 min) at 28% VO2max. Air movement was 0.75 m.s-1. The initial test and the 16th test on each subject both done at 50 degrees C and 30 Torr (32% rh). Each subject did the intervening 14 experiments twice per day at varying ambient temperature (Ta) and water vapor pressure (Pa) levels, so selected to progressively increase skin wettedness levels. Mean skin temperature (Tsk) and esophageal temperature (Tes), heart rate (HR), skin evaporative heat loss (Esk), and warm discomfort were continuously observed. Skin wettedness (w) was evaluated as the ratio of the observed Esk to the maximum evaporative capacity of the environment. A rational effective temperature (ET) is defined as the dry bulb temperature at 50% rh in which the total heat exchange from skin surface would be the same as in the test environment, described by the observed Ta and Pa. The results showed that 1) during steady state both HR and Tes were unaffected by Ta from 26 to 41 degrees C responding to the level of exercise intensity, when Pa less than or equal to 20 Torr; 2) both mean body temperature, found by weighting Tsk:Tes by 1:9, and ET were each significant indicators of physiological strain when Pa greater than 20 Torr; 3) a level of strain, caused by skin wettedness values greater than 0.5, is suggested as a primary condition necessary for inducing heat acclimation.

Acclimatization↗
PubMed1977

Evaporation of sweat from sedentary man in humid environments.

UNLABELLED: Physiological and sensory responses were observed in four male subjects while they were seated on a balance. The chamber temperature always equaled mean skin (Tsk)(34-36 degrees C), thus eliminating all sensible heat transfer. Ambient water vapor pressure (Pa) was increased in steps from 10 to 40 Torr. Tests at air velocities from 0.1 to 2.4 m/s were conducted with subjects nude and clothed. Esophageal temperature (Tes) and Tsk, heat rate (HR) and weight loss (M) were measured throughout the 2.5-h tests. After each 25-min humidity step subjects recorded their warm discomfort, sensation of sweating, and thermal sensation. RESULTS: Tsk, HR, and M were unaffected by humidity until critical Pa (P a crit) was reached above which M decreased and Tsk and HR increased rapidly. P a crit decreased with clothing and decreasing velocity. Tes remainded relatively constant throughout the tests. Sweating, discomfort and temperature sensations increased gradually with increasing Pa. Above P a crit sweating and discomfort sensations accelerated markedly. Mass transfer coefficients and clothing vapor conductance factors were evaluated. Skin wettedness at Pa crit decreased from 74% at 0.1 m/s to 35% at 2.4 m/s.

Adolescent↗
PubMed1976

Prediction of equivalent environments by energy exchange and assessments of physiological strain and discomfort.

The described equivalence postulate was confirmed experimentally by examining physiological responses as well as discomfort sensation in a series of predicted equivalent conditions during exercise (congruent to 3 met). ET or the equivalent Ta at 50% RH is a single independent variable that is uniquely related to the mean skin temperature (Tsk), skin wettedness (w), body core temperature (Tcore) and sense of discomfort.

Body Temperature Regulation↗