Cardiac function at rest and during submaximal work under acute hypobaric hypoxia.
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概要
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In order to assess the effects of acute hypobaric hypoxia on the cardiac pump function at supine rest and during supine submaximal pedaling work, non-invasive methods of the systolic time intervals (STI's) and impedance cardiography were applied. The experimental conditions were a control (SL: sea level), 4, 000 m, 5, 000 m and 6, 000 m simulated altitudes. Five healthy males were participated as the subjects. The following results were obtained.<BR>I) At supine rest; (1) Although heart rate (HR) increased significantly at over 4, 000 m compared to that of SL, no significant change in cardiac output (Q) and stroke volume (SV) was observed. (2) The QS<SUB>2</SUB> (total electromechanical systole) and LVET (left ventricular ejection time) significantly decreased at over 4, 000 m. (3) The PEP/LVET ratio decreased with increase of altitudes, and was significant at 6, 000 m compared to that of SL.<BR>II) Submaximal work; (1) Although HR increased linearly with the increment of work load, HR during the work under simulated altitudes was always significantly higher than that of SL. However, no significant difference in SV and Q was observed although SV during work under hypoxia showed always lower values than that of SL. (2) The QS<SUB>2</SUB>, LVET and PEP progressively decreased from SL to 75 watt of work in each altitude. These changes except PEP at 75 watt of work were significant at over 4, 000 m compared to those at SL. (3) Although the PEP/LVET ratio at each altitude except 6, 000 m decreased from rest to 50 watt of work, it tended to increase at 75 watt of work. From the results described above, it might be concluded that (1) the left ventricular function at supine rest is enhanced by the acute hypobaric hypoxia, (2) the myocardial contractility is enhanced until the light work and then tends to be deteriorated at more heavier work under acute hypobaric hypoxia.
- 日本生気象学会の論文
日本生気象学会 | 論文
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