Sleep apneas in high altitude residents (3,800 m).

The question is: to what extent periodic breathing usually observed in translocated subjects at high altitude affects normal and polycythemic residents of high altitude? Standard sleep parameters, chest wall movements, temperature of ventilated gas and arterial O2 saturation (SaO2) were continuously recorded in 7 normal highlanders (mean hematocrit: 51%) and 14 polycythemic highlanders (mean hematocrit: 68%) during one night in La Paz, 3,850 m, Bolivia. The patterns of breathing instability were analysed by two ways: measuring duration of apneas and counting all the oscillations of SaO2 greater than 1%. Normal and polycythemic highlanders displayed a wide intersubject variability with regard to breathing instability, hence no significant difference in the total number of apneas and oscillations of SaO2 could be evidenced between the 2 groups. However, the longest apneas and the highest number of oscillations of SaO2 were found in the polycythemic highlanders.

Does arterial PCO2 interfere with hypoxia in muscular metabolism in man?

To answer the question whether PCO2 affects the muscular metabolism, PO2, PCO2, pH, lactic acid concentration and hemoglobin were measured in the efferent muscular venous blood from common flexor digitorum, during forearm rhythmic exercise corresponding to VO2max. Exercise was carried out either in hypocapnic hypoxia i.e. in permanent high altitude residents and translocated lowlanders, or in hypercapnic hypoxia i.e. in chronic obstructive lung disease (COLD) patients. The results show that, during exercise: i) PO2 in muscular venous blood remains around 20 Torr in normoxia and hypocapnic hypoxia and even higher (25 torr) in COLD patients, despite low arterial PaO2, and ii) arterial and/or local PCO2 play a role in the control of the muscular blood flow. But we cannot conclude that a change in PaCO2 affects muscular metabolism itself, because lactic acid in the muscular venous blood, that we used to check this effect, is likely dependent on mechanisms other than anaerobic glycolysis, such as a change in lactic acid efflux from the myocytes. The increase in muscular venous PCO2 may enhance the myocyte permeability to lactic acid during exercise.

Changes in rectal and mean skin temperature in response to suggested heat during hypnosis in man.

Rectal temperature, mean skin temperature and heart rate were recorded in 7 subjects during hypnosis, induced either alone or while sensations of heat were suggested. During hypnosis alone, a fall in the heart rate of about 10 beat X min-1 was the only autonomic response observed; body temperatures were unaltered. In contrast, during hypnosis with suggestion of heat, the following changes occurred: (1) Mean rectal temperature decreased 0.20 degrees C (p less than 0.05) within 50 min. Its mean time course differed significantly from that for hypnosis alone (p less than 0.001). (2) Comparison of individual rectal temperature time sequences showed that in fact this temperature only declined in 4 subjects out of 7, and tended to form a plateau located 0.35 degrees C below the value of the preceding waking state. Despite reinforcement of heat suggestion, the plateau continued until the end of the hypnotic trance. (3) Mean skin temperature tended to rise. (4) When hypnosis with suggestion ceased, both rectal and skin temperatures very slowly returned to their levels during the preceding waking state.

Intersubject viability in growth hormone time course during different types of work.

This study addresses the question of variability of immunoreactive human growth hormone (IRHGH) response to the following types of muscular exercise. 1) One hour of submaximal exercise with restarting for 30 min after 20 min of recovery. Three types of responses were observed: a rise of [IRHGH] occurred in response to muscular activity; [IRHGH] was maintained at rest level during the first bout and then rose in the second bout; or [IRHGH] rose during the first bout and was no longer modified by the restarting. 2) Thirty minutes of heavy exercise. In some subjects [IRHGH] change was almost linear with time, reaching very high values and dropping as soon as exercise had stopped, whereas in others peak values were similar to those of submaximal exercise but, in contrast, plateaued during recovery. 3) One hour of exercise performed either continuously or with alternate sequences of 30-s exercise and 30-s pause. In intermittent exercise, some subjects displayed a similar time course of [IRHGH] as in continuous exercise and others displayed markedly high values. 4) One hour of submaximal exercise at three different intensities carried out at ambient temperatures of 24 and 33 degrees C. At 33 degrees C, in some subjects, [IRHGH] time course at the three intensities was unchanged at 33 degrees C compared with that at 24 degrees C, whereas the maximal value increased in another subject up to 150 ng X ml-1. A significant intrasubject consistency to a given type of exercise was evident over several months. The study emphasizes that caution should be used in drawing definite conclusions from averaged results with high variability.

Time course of plasma growth hormone during exercise in humans at altitude.

The effects of hypoxia on growth hormone release during submaximal exercise were studied 1) in eight highlanders (HL) at 3,800 m (La Paz, Bolivia); and 2) in five lowlanders (LL) at sea level, after 5 days' sojourn at 2,850 m, and while breathing a hypoxic gas mixture (FIO2 - 0.15 corresponding to PIO2 at 2,850 m) 1 mo after returning to sea level. Concentrations of immunoreactive human growth hormone ([IRHGH]), blood glucose ([G]), free fatty acids ([FFA]), and lactate ([LA]) were determined repeatedly at rest, during 1 h of exercise, and after 1 h of recovery. Compared with LL, in HL, the resting value of [IRHGH] is higher, the rate of increase at the beginning of exercise is faster and earlier, but the mean maximal value reached at the end of exercise is similar. The response pattern in LL during the early stages of exposure to hypoxia resembles that of HL. No correlation was found between peak values of [IRHGH] and maximal values of [LA] and [FFA] or minimal values of [G]. The possible causes of the different time sequence observed in growth hormone dynamics during hypoxia are suggested: an alteration of the clearance of the hormone through a more pronounced reduction of hepatic blood flow or a difference in the state of the pituitary gland before the exercise begins. The study emphasizes the importance of characterizing time sequence of [IRHGH] by parameters other than the maximal value, e.g., by mean concentration computed over exercise period.