Ventilation and hypoxic ventilatory response of Tibetan and Aymara high altitude natives

Abstract

Newcomers acclimatizing to high altitude and adult male Tibetan high altitude natives have increased ventilation relative to sea level natives at sea level. However, Andean and Rocky Mountain high altitude natives have an intermediate level of ventilation lower than that of newcomers and Tibetan high altitude natives although generally higher than that of sea level natives at sea level. Because the reason for the relative hypoventilation of some high altitude native populations was unknown, a study was designed to describe ventilation from adolescence through old age in samples of Tibetan and Andean high altitude natives and to estimate the relative genetic and environmental influences. This paper compares resting ventilation and hypoxic ventilatory response (HVR) of 320 Tibetans 9-82 years of age and 542 Bolivian Aymara 13-94 years of age, native residents at 3,800-4,065 m. Tibetan resting ventilation was roughly 1.5 times higher and Tibetan HVR was roughly double that of Aymara. Greater duration of hypoxia (older age) was not an important source of variation in resting ventilation or HVR in either sample. That is, contrary to previous studies, neither sample acquired hypoventilation in the age ranges under study. Within populations, greater severity of hypoxia (lower percent of oxygen saturation of arterial hemoglobin) was associated with slightly higher resting ventilation among Tibetans and lower resting ventilation and HVR among Aymara women, although the associations accounted for just 2-7% of the variation. Between populations, the Tibetan sample was more hypoxic and had higher resting ventilation and HVR. Other systematic environmental contrasts did not appear to elevate Tibetan or depress Aymara ventilation. There was more intrapopulation genetic variation in these traits in the Tibetan than the Aymara sample. Thirty-five percent of the Tibetan, but none of the Aymara, resting ventilation variance was due to genetic differences among individuals. Thirty-one percent of the Tibetan HVR, but just 21% of the Aymara, HVR variance was due to genetic differences among individuals. Thus there is greater potential for evolutionary change in these traits in the Tibetans. Presently, there are two different ventilation phenotypes among high altitude natives as compared with sea level populations at sea level: lifelong sustained high resting ventilation and a moderate HVR among Tibetans in contrast with a slightly elevated resting ventilation and a low HVR among Aymara.

Oxygen Saturation Increases During Childhood and Decreases During Adulthood Among High Altitude Native Tibetans Residing at 3800–4200 m

“…After placing the sensor on the finger or toe, the research assistant waited until a reading registered on the oximeter display, waited another 10-15 sec to verify a steady signal, and then began recording SaO 2 and pulse using the Criticare model 550 printer module programmed to record every 10 sec. Six observations were recorded and their average was used as the individual's SaO 2 as in previous studies (Beall et al, 1992(Beall et al, , 1994(Beall et al, , 1997a(Beall et al, , 1999Beall and Goldstein, 1990). The repeatability of the SaO 2 measurements was evaluated by remeasuring 65 people and calculating the average difference between the two measurements on different days (Bland and Altman, 1986).…”

Landscapes of death: GIS-based analyses of chullpas in the western Lake Titicaca basin

“…Earth curvature and refraction were corrected in ArcGIS. Based on ethnographical research performed in the Lake Titicaca basin, the average height of inhabitants is 1.5 m (Beall et al, 1997). An offset representing the height of onlookers was therefore set at 1.5 m. Considering that the viewer to-from heights are similar (1.5 m), the viewsheds most likely delineate the whole area from which the chullpas could be visible.…”

Lessons in hypoxic adaptation from high-altitude populations

“…Using this approach, Tibetan populations exhibit significant heritability in hemoglobin concentration (h 2 ∼0.65), percent of oxygen saturation of hemoglobin (h 2 ∼0.67), resting ventilation (h 2 ∼0.57), and hypoxic ventilatory response (∼0.64), while Andean populations have significant heritability in hemoglobin concentration (h 2 ∼0.89) and hypoxic ventilatory response (h 2 ∼0.50) but not ventilation or oxygen saturation [10][11][12]. These contrasts suggest population differences in the strength of inheritance of some major factors in oxygen uptake and delivery.…”