(Table 1) Characteristics of South Pole personnel according to forced expiratory flow (FEF25-75) response to altitude

The impact of acute altitude exposure on pulmonary function is variable. A large inter-individual variability in the changes in forced expiratory flows (FEFs) is reported with acute exposure to altitude, which is suggested to represent an interaction between several factors influencing bronchial tone such as changes in gas density, catecholamine stimulation, and mild interstitial edema. This study examined the association between FEF variability, acute mountain sickness (AMS) and various blood markers affecting bronchial tone (endothelin-1, vascular endothelial growth factor (VEGF), catecholamines, angiotensin II) in 102 individuals rapidly transported to the South Pole (2835 m). The mean FEF between 25 and 75% (FEF25-75) and blood markers were recorded at sea level and after the second night at altitude. AMS was assessed using Lake Louise questionnaires. FEF25-75 increased by an average of 12% with changes ranging from -26 to +59% from sea level to altitude. On the second day, AMS incidence was 36% and was higher in individuals with increases in FEF25-75 (41 vs. 22%, P = 0.05). Ascent to altitude induced an increase in endothelin-1 levels, with greater levels observed in individuals with decreased FEF25-75. Epinephrine levels increased with ascent to altitude and the response was six times larger in individuals with decreased FEF25-75. Greater levels of endothelin-1 in individuals with decreased FEF25-75 suggest a response consistent with pulmonary hypertension and/or mild interstitial edema, while epinephrine may be upregulated in these individuals to clear lung fluid through stimulation of beta2-adrenergic receptors.

急性高原暴露对肺功能的影响存在个体差异。已有研究报道，急性高原暴露后用力呼气流量（forced expiratory flows, FEFs）的变化存在显著的个体间变异，该变异被认为是多种影响支气管张力的因素共同作用的结果，包括气体密度改变、儿茶酚胺刺激以及轻度间质性水肿。本研究纳入102名快速转运至南极点（海拔2835米）的受试者，探讨了FEFs变异度、急性高原病（acute mountain sickness, AMS）与多种影响支气管张力的血液标志物（内皮素-1、血管内皮生长因子（vascular endothelial growth factor, VEGF）、儿茶酚胺、血管紧张素II）之间的关联。研究分别在海平面及抵达高原后的第二夜，记录了受试者25%~75%用力呼气流量（FEF25-75）的平均值及上述血液标志物水平；采用路易斯湖问卷对急性高原病进行评估。从海平面至高原环境，FEF25-75平均升高12%，个体间变化范围为-26%至+59%。抵达高原后次日，急性高原病的总发病率为36%，其中FEF25-75升高的受试者发病率（41%）显著高于FEF25-75未升高者（22%，P=0.05）。高原暴露可使内皮素-1水平升高，且FEF25-75降低的受试者内皮素-1水平升高更为显著。肾上腺素水平随高原暴露而升高，在FEF25-75降低的受试者中，肾上腺素的升高幅度是其他受试者的6倍。FEF25-75降低的受试者体内更高的内皮素-1水平，提示其存在与肺动脉高压和/或轻度间质性水肿一致的病理生理反应；而此类受试者体内肾上腺素的上调，可能通过刺激β2肾上腺素能受体以清除肺内液体。