ヒマラヤ地域住民に観察される化学受容器反射感受性の亢進

Abstract

Aim: Humans adjusted to ambient hypoxia via the alteration of chemoreceptor reflex sensitivity. However, it has not yet been established how we can measure it. Thus, the aim of this investigation is to propose a method how to measure it using a newly developed pulse oximetry monitor. Methods: We assessed it as a relation between a phasic change of hypoxemic condition and an alteration of heart rate. We planned two types of investigations. Effects of high altitude on pulse oximetry (SpO2) and heart rate (HR) were observed by 25-minute continuous monitoring of SpO2 and HR. The first study was done in 3 healthy subjects (29-year and 56-year women and a 59-year man) along with a trip for about 10 days from Japan to Himalayan valley. More than 6 times of measurement of SpO2 and HR were done before and during the trip. Another observation of the 25-minute continuous monitoring was done in 44 Ladakhi priests (17-90 years men, average 49.1 years of age) living at an altitude of 2, 500 to 3, 720 meters. Results: SpO2 and HR were simultaneously monitored each cardiac beat in each subject. As an index of chemoreceptor reflex sensitivity (CRS), we measured a slope of the fitting line, showing a correlation between a prominent decrease of SpO2 and a phasic increase in HR. First investigation showed CRS changed from 0 msec/% at Japan before a trip to 42.5 msec/% during a trip at Himalayan valley. The second investigation showed higher measures of CRS of the 44 priests, average 46.1 msec/%, ranged from 3.3 to 148.5 msec/%. People living at high altitude have a higher sensitivity of chemoreceptor reflex compared to the low-latitude peers, although it has been fully habituated and fully adapted. Conclusions: We need a glocal, i.e., global and local, comprehensive assessment (GCA), including a measurement of CRS, for a more fruitful treatment. Longitudinal observations of GCA should help us to prevent strokes and other cardiovascular events, especially at high-altitude.