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Biomedical subjects

H Marotte

Publications and source records attributed to H Marotte.

28 records · Page 2Linked to original sources
PubMed1988

Testing of the Eschweiler 2500-11 blood gas analyser during inflight conditions.

Measurement of blood gas values during air transport of intensive care patients must take into account the extreme inflight variations in pressure. We tested the accuracy and reliability of the Eschweiler 2500-11 apparatus, with its incorporated pressure transducer, on four different gas mixtures equilibrated with fresh blood at two different altitudes simulated in a decompression chamber. Results for the pressure transducer show: 1) concordance of pressure values with those of ground instrumentation; 2) stable response; and 3) absence of hysteresis. Gas measurement electrodes were shown to have linear responses and were accurate for all tested values except very low PCO2 and very high PO2 figures. We conclude that the performance of this device is satisfactory during inflight conditions.

Aerospace Medicine↗
PubMed1986

Circadian variations of systolic time intervals.

In order to test the reality of a circadian evolution of systolic time intervals, an experiment was conducted on six subjects resting in a supine position for 24 h. Heart rate (HR), systole (S), diastole (D), presystole (PS), isovolumetric contraction time (IVCT), normal and corrected ventricular pre-ejection and ejection time (LPEP, LPEPc, LVET, LVETc) were computed by electric rheoplethysmography every 3 h in supine and sitting positions. Evidence of the existence of a circadian rhythm was clear in supine subjects; especially LPEP and LVET acrophases were, respectively, 4.03 +/- 2.36 h and 4.31 +/- 1.15 h. In sitting subjects, a circadian rhythm was evidenced for IVCT, LVETc and LPEP/LVET, and on the difference of resting-sitting for PS, IVCT and LPEP, suggesting a decrease in orthostatic tolerance at the end of the night. However, values for characteristics of circadian rhythms (mean, amplitude, phase) strongly depend upon experimental conditions (position, activity, diet). A phase difference between systolic times and HR was also observed. This phenomenon was due to an advance in phase of D relative to S. Finally, all these results show that it is always necessary to take circadian factors into consideration during cardiovascular studies, especially for the preparation of protocols and the interpretation of results.

Adult↗
PubMed1982

[Ultradian respiratory rhythms in groups of Sprague-Dawley rats of both sexes].

Spectral analysis of the carbon dioxide emitted in controlled environmental conditions (temperature: 20-21 degrees C; humidity: 50-60%; lighting: 150 lux in LD12-12; background noise: 70 dB), by groups of 14 month old Sprague Dawleys, shows ultradian respiratory rates with periods of a 107-72 minute range for males and 107-45 minute for females. Moreover, VCO2 related to body weight is higher in females than in males.

Animals↗
PubMed1982

The application of variance analysis to the study of biological rhythms of known periods.

This paper describes a statistical technique which permits study of, for example, complex biological rhythms with a known fundamental period. This technique uses the principles of variance analysis. The main calculation phases are: the regression calculation on a periodic time function; the study (by variance analysis) of the validity of the mathematical model; the study of the parallelism between subjects; and, finally, the study of the significance of each harmonic component. The calculation is completed by determining confidence intervals: those of the harmonic function parameters, followed by those of the function extremes.

Analysis of Variance↗
PubMedDate not supplied

Circadian rhythm of thermoregulating responses in man exposed to thermal stimuli.

Circadian changes in man's thermoregulating responses were studied in two experimental runs during which 7 volunteer subjects were exposed at 8 equally spaced time points of the 24-h span to a quick rise in temperature (To = 40 degrees C, v = 1 m/sec, P H2O less than 1 kPa) or to progressive cooling, the final temperature being reached after 45 min (To = 20 degrees C, v = 0.2 m/sec, P H2O less than 1 kPa). Under heat exposure, a circadian rhythm was observed in the period preceding the onset of sweating, and also in rectal temperature and mean body temperature, both at the onset of sweating and at its steady state. The time constant of the sweating rate and the sweating rate at the steady state show no apparent changes. Under cold exposure there is no detectable circadian rhythm in the mean body temperature at the onset of shivering, however, a circadian evolution appears in rectal temperature at the onset of shivering and at the end of the experiment. A circadian rhythm also appears for the metabolic response at the end of the experiment. These results suggest the presence of a circadian rhythm of the set point with no change in the gain of sweat responses. They also imply that thermoregulating responses to cold follow circadian changes.

Body Temperature↗
PubMedDate not supplied

Circadian rhythm of temperature in man. Comparative study with two experiment protocols.

The circadian rhythm of rectal and skin temperature was studied in man at rest and at thermal neutrality according to two different protocols, to make allowance for the experimental conditions. In the first case, ambient temperature (To) was maintained at a constant value close to thermal neutrality and mean skin temperature (Ts) could evolve freely for 24 h. In the second case, Ts was maintained at 34 degrees C by adequately adjusting To during 90 min-periods divided into 8 equidistant points of the 24-h spans. The results were comparable and brought out a rhythm of rectal temperature (Tre) of a low amplitude, non sinusoidal, with a day-time plateau and a night-time minimum. The Ts and body conductance rhythm, the lack of metabolism and evaporative thermolysis rhythm led to us to confer a major role to the circulatory phenomena to explain the Tre rhythm in these experiments.

Adult↗