Biomedical subjects

Igor B Mekjavic

Publications and source records attributed to Igor B Mekjavic.

5 recordsLinked to original sources

PubMed2003

Effect of hypoxia on preferred hand temperature.

INTRODUCTION: Selection of preferred skin temperature is a consequence of complex central neural integration of thermoafferent information in the polysynaptic pathway for behavioral thermoregulation. The present study tested the hypothesis that hypoxia alters behavioral temperature regulation. METHODS: Eight male volunteers participated in two separate trials. In each trial they were immersed in 28 degrees C water for 90 min, and inspired either room air (air trial) or a hypoxic gas mixture (hypoxia trial; 11.5% O2/88.5% N2). Their left hand was placed in a separate bath perfused with water. At regular intervals they were instructed to adjust the temperature of the water perfusing the hand bath to a comfortable temperature, defined as the 'preferred hand temperature' (Tpref). At minute intervals, esophageal (Tes), rectal (Tre), and skin (Tsk) temperatures, along with heat flux from the skin (Q) and ventilation (VI) were recorded. The observed responses were compared with a one-way ANOVA. RESULTS: With the exception of VI, there were no significant differences in any of the recorded variables between the two conditions. During the immersion, Tes and Tre decreased by 1.0 and 0.7 degrees C, respectively, in the air trial, and by 0.8 and 0.7 degrees C, respectively, in the hypoxia trial. Concomitant with decreases in core temperature, there was a significant increase (p < 0.05) in Tpref of 2.1 degrees C in the air trial and 2.4 degrees C in the hypoxia trial. The difference in Tpref between the air and hypoxia trials was not significant. DISCUSSION: Assuming that the selection of preferred hand temperature represents a behavioral thermoregulatory response, the present results suggest that moderate normobaric hypoxia does not affect human behavioral thermoregulation.

Adult↗

PubMed2002

Inhalation of warm and cold air does not influence brain stem or core temperature in normothermic humans.

The present study tested the hypothesis that inhalation rewarming provides a thermal increment to central neural structures adjacent to the nasopharyngeal region. Auditory-evoked brain stem responses of 14 subjects (7 men and 7 women) were monitored for 25 min while they inspired room air (24 degrees C) followed by hot air (41 degrees C) saturated with water vapor and cold dry air (-1 degrees C). The latencies of peaks I, III, and V and the interpeak latencies (IPLs) I-III, III-V, and I-V were compared among the three conditions with a repeated-measures ANOVA. Changes in IPLs are sensitive markers of changes in brain stem temperature. Tympanic temperature (T(ty)) was measured with an infrared tympanic thermometer. There were no significant differences in T(ty), peak latencies I, III, and V, and IPLs I-III, III-V, and I-V. The results indicate that inhalation of hot and cold air does not influence T(ty), nor does it influence the temperature of the brain stem. We conclude that inhalation rewarming is not capable of warming the vital central neural structures adjacent to the naropharynx.

Adult↗

PubMed2002

Visual function after prolonged bed rest.

The present study evaluated the claim of earlier reports, that of bed rest-induced alterations in visual function. Indices of visual function were studied in 10 healthy male subjects, during 35 days of horizontal bed rest. Before and after the 35 day bed rest, both eyes of all subjects were examined for visual acuity, intraocular pressure, contrast sensitivity, stereopsis and visual field. Pre- and post-bed rest values were compared with Student's T-test. There were no significant differences in any of the measured indices of visual function.

Journal Article↗

PubMed2002

Influence of active recovery following prolonged bed rest on static exercise pressor response.

The present study investigated the effect of active recovery, following 35 days of horizontal bed rest, on the magnitude and time course of the pressor and heart rate responses to sustained 90 minute submaximal isometric contraction of unilateral knee extensor muscles. Ten healthy male subjects were tested immediately post bed rest (Post BR) and again after 4 weeks of active recovery (Recovery). In both trials subjects sustained an absolute force equal to 30% of Post BR maximal voluntary contraction (MVC). Beat-to-beat heart rate (HR) and mean arterial blood pressure (MAP) were monitored continuously during sustained contraction using the volume-clamp technique. Despite a 24% increase in MVC, there were no significant differences in the magnitudes of HR and MAP responses between Post BR and Recovery trials, suggesting a bed rest-induced attenuation of the static exercise pressor response.

Journal Article↗

PubMed2002

Core temperature circdian rhythm during 35 days of horizontal bed rest.

The present study evaluated whether the previously reported alterations in core temperature circadian rhythm associated with bed rest might be attributable to increased heat loss from the skin. Infra-red thermograms were obtained at weekly intervals during 5 weeks of bed rest and after 4 weeks of active recovery. Tympanic temperature (Tty) was measured at hourly intervals from 0800 to 2300 hrs on similar occasions during bed rest. There were no significant changes in mean tympanic temperature or amplitude of Tty circadian rhythm during the 5 week bed rest period. Skin temperature decreased progressively during bed rest (P<0.005), with distal regions being the most affected.

Journal Article↗