Association Between Lung Function And High Altitude Adaptation Among Native Tibetan Residents Living At Different Altitude

ObjectiveTo better understand how the body adapts to the high altitude hypoxia environment,the present study was conducted to compare the variations of lung ventilation function among Tibetan residents living at 2227 m,3660m,4500 m and 5018 m above sea level.MethodsA total of 980 Tibetan residents who living in four different elevation gradients were selected by accidental sampling,which includes 282 in Yigong（2227 m）,319 in Lhasa（3660 m）,168 in Guoqing（4500 m）and211 in Pumajiangtang（5018 m）.There were 502 males and 478 females.Lung function,blood oxygen saturation,hemoglobin concentration,heart rate and anthropometric indicators were measured.The inclusion criteria were the native Tibetans who are over 18 years old,over three generations living in the plateau,and have no intermarriage experience of other ethnic groups within three generations.The exclusion criteria were those with a history of upper respiratory tract infection and cardiopulmonary dysfunction in the past month.Anthropometric and physiological indicators were expressed as mean±SD.Single-factor ANOVA analysis was used for the comparison of pulmonary ventilation function indexes among different elevations,while covariance analysis was used for the comparison of lung function after adjustment,and multivariate linear regression analysis was applied to analyze the correlation between variables.P<0.05 was considered as statistically significant.ResultsHeight,weight and arterial oxygen saturation decreased with elevation,while hemoglobin concentration increased with elevation（P<0.05）.There was no significant difference in chest circumference and abdominal circumference between native Tibetans living at four altitudes.Before the adjusting,the mean values of FVC,FEV₁,PEF,FEF25%and FEF50%of residents in Guoqing were significantly higher than those in Yigong,Lhasa and Pumajiangtang（4500 m>3660 m>2227 m>5018m）.Moreover,FVC,PEF and FEF25%had significant differences between different elevations（P<0.05）,while FEV₁ and FEF50%had significant variations between Lhasa and Guoqing,and between Guoqing and Pumajiangtang（P<0.05）.After adjusting for gender,age,height,weight,chest circumference and aterial oxygen saturation,the mean values of FVC,FEV₁,PEF,FEF25%and FEF50%of residents in Guoqing were significantly higher than those in Yigong,Lhasa and Pumajiangtang（P<0.05）.The pulmonary ventilation function of Tibetan residents increases with altitude（2227 m<3660 m<4500 m）,but Tibetan residents living at an altitude of 5018 m had less valued of lung ventilation function than those who living in 4500 m above sea level.ConclusionAlthough the higher the altitude,the more compensatory the pulmonary ventilation function,in order to meet the oxygen demand of the body,when the elevation reaches a certain level,the pulmonary ventilation function cannot be further compensated with the elevation.Thus,it can be speculated that there is a limit to the compensation of pulmonary ventilation function.It is suggested that lung function will no longer be enhanced when altitude increases beyond the body’s capacity to regulate.