Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada.
Department of Physiology, School of Medicine, College of Medicine & Health, University Cork College, Cork, Ireland.
Exp Physiol. 2024 Jul;109(7):1080-1098. doi: 10.1113/EP091748. Epub 2024 May 15.
High altitude (HA) ascent imposes systemic hypoxia and associated risk of acute mountain sickness. Acute hypoxia elicits a hypoxic ventilatory response (HVR), which is augmented with chronic HA exposure (i.e., ventilatory acclimatization; VA). However, laboratory-based HVR tests lack portability and feasibility in field studies. As an alternative, we aimed to characterize area under the curve (AUC) calculations on Fenn diagrams, modified by plotting portable measurements of end-tidal carbon dioxide ( ) against peripheral oxygen saturation ( ) to characterize and quantify VA during incremental ascent to HA (n = 46). Secondarily, these participants were compared with a separate group following the identical ascent profile whilst self-administering a prophylactic oral dose of acetazolamide (Az; 125 mg BID; n = 20) during ascent. First, morning and measurements were collected on 46 acetazolamide-free (NAz) lowland participants during an incremental ascent over 10 days to 5160 m in the Nepal Himalaya. AUC was calculated from individually constructed Fenn diagrams, with a trichotomized split on ranked values characterizing the smallest, medium, and largest magnitudes of AUC, representing high (n = 15), moderate (n = 16), and low (n = 15) degrees of acclimatization. After characterizing the range of response magnitudes, we further demonstrated that AUC magnitudes were significantly smaller in the Az group compared to the NAz group (P = 0.0021), suggesting improved VA. These results suggest that calculating AUC on modified Fenn diagrams has utility in assessing VA in large groups of trekkers during incremental ascent to HA, due to the associated portability and congruency with known physiology, although this novel analytical method requires further validation in controlled experiments. HIGHLIGHTS: What is the central question of this study? What are the characteristics of a novel methodological approach to assess ventilatory acclimatization (VA) with incremental ascent to high altitude (HA)? What is the main finding and its importance? Area under the curve (AUC) magnitudes calculated from modified Fenn diagrams were significantly smaller in trekkers taking an oral prophylactic dose of acetazolamide compared to an acetazolamide-free group, suggesting improved VA. During incremental HA ascent, quantifying AUC using modified Fenn diagrams is feasible to assess VA in large groups of trekkers with ascent, although this novel analytical method requires further validation in controlled experiments.
高海拔（HA）上升会导致全身缺氧和急性高山病的相关风险。急性缺氧会引起低氧性通气反应（HVR），而慢性 HA 暴露会增强这种反应（即通气适应；VA）。然而，实验室的 HVR 测试在野外研究中缺乏便携性和可行性。因此，我们的目标是通过绘制便携式测量的呼气末二氧化碳（ ）与外周血氧饱和度（ ）的 Fenn 图来描述和量化递增上升到 HA 期间的 VA（n = 46）。其次，将这些参与者与另一组进行比较，后者在上升过程中自行服用预防性口服乙酰唑胺（Az；125 mg BID；n = 20），并遵循相同的上升曲线。首先，在尼泊尔喜马拉雅山的 10 天内，46 名未服用乙酰唑胺（NAz）的低地参与者在逐渐上升至 5160 米的过程中，每天早上收集 和 的测量值。从单独构建的 Fenn 图中计算 AUC，根据排序值进行三分法划分，以表征 AUC 的最小、中大和最大幅度，分别代表高（n = 15）、中（n = 16）和低（n = 15）的适应程度。在描述了反应幅度的范围后，我们进一步表明，与 NAz 组相比，Az 组的 AUC 幅度明显较小（P = 0.0021），这表明 VA 得到了改善。这些结果表明，由于便携性和与已知生理学的一致性，在递增上升到 HA 的过程中，使用改良 Fenn 图计算 AUC 对评估徒步旅行者的 VA 具有实用性，尽管这种新的分析方法需要在对照实验中进一步验证。
