Abstract
Insufficient cardiorespiratory compensation is closely associated with acute hypoxic symptoms and high-altitude (HA) cardiovascular events. To avoid such adverse events, predicting HA cardiorespiratory fitness impairment (HA-CRFi) is clinically important. However, to date, there is insufficient information regarding the prediction of HA-CRFi. In this study, we aimed to formulate a protocol to predict individuals at risk of HA-CRFi. We recruited 246 volunteers who were transported to Lhasa (HA, 3,700 m) from Chengdu (the sea level [SL], <500 m) through an airplane. Physiological parameters at rest and during post-submaximal exercise, as well as cardiorespiratory fitness at HA and SL, were measured. Logistic regression and receiver operating characteristic (ROC) curve analyses were employed to predict HA-CRFi. We analyzed 66 pulmonary vascular function and hypoxia-inducible factor- (HIF-) related polymorphisms associated with HA-CRFi. To increase the prediction accuracy, we used a combination model including physiological parameters and genetic information to predict HA-CRFi. The oxygen saturation (SpO2) of post-submaximal exercise at SL and EPAS1 rs13419896-A and EGLN1 rs508618-G variants were associated with HA-CRFi (SpO2, area under the curve (AUC) = 0.736, cutoff = 95.5%, p < 0.001; EPAS1 A and EGLN1 G, odds ratio [OR] = 12.02, 95% CI = 4.84–29.85, p < 0.001). A combination model including the two risk factors—post-submaximal exercise SpO2 at SL of <95.5% and the presence of EPAS1 rs13419896-A and EGLN1 rs508618-G variants—was significantly more effective and accurate in predicting HA-CRFi (OR = 19.62, 95% CI = 6.42–59.94, p < 0.001). Our study employed a combination of genetic information and the physiological parameters of post-submaximal exercise at SL to predict HA-CRFi. Based on the optimized prediction model, our findings could identify individuals at a high risk of HA-CRFi in an early stage and reduce cardiovascular events.
Highlights
Many people worldwide enjoy mountain hiking at high altitudes (HAs); most individuals have never been to a mountain peak and are unaware of the cardiorespiratory fitness requirements for such activities [1]
heart rate (HR) and systolic blood pressure (SBP) increased, but SpO2 reduced at both sea level (SL) and HA compared to the baseline levels
The most noteworthy finding was that the combination of information regarding post-submaximal exercise SpO2 at and genetic information significantly improved the prediction of HA cardiorespiratory fitness impairment (HA-CRFi), compared to the use of SpO2 alone or genetic information alone
Summary
Many people worldwide enjoy mountain hiking at high altitudes (HAs); most individuals have never been to a mountain peak and are unaware of the cardiorespiratory fitness requirements for such activities [1]. Previous studies showed that hypobaric hypoxia impaired exercise capacity [2] and cardiorespiratory fitness [3, 4], which increased the risk of cardiovascular events in such hypoxic environments [5]. It is crucial to identify individuals who may experience cardiorespiratory fitness impairment (CRFi) before engaging in physical activity at HA. Previous studies have indicated that cardiorespiratory performance (evaluated by maximum oxygen consumption, VO2max) decreases by 1.5–3.5% for every 300 m of additional elevation above 1,500 m [6]. This decline is more pronounced at altitudes above 5,000 m [7]. HA-induced decreases in arterial oxygenation and pulmonary capillary distensibility are associated with CRFi, the mechanisms that determine this effect in hypoxia remain unknown [11] and little information on predicting CRFi has been reported worldwide
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