Faculty of Biology and Medicine, ISSUL, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland.
Med Sci Sports Exerc. 2013 Feb;45(2):253-60. doi: 10.1249/MSS.0b013e31826d5aa2.
Slight differences in physiological responses and nitric oxide (NO) have been reported at rest between hypobaric hypoxia (HH) and normobaric hypoxia (NH) during short exposure.Our study reports NO and oxidative stress at rest and physiological responses during moderate exercise in HH versus NH.
Ten subjects were randomly exposed for 24 h to HH (3000 m; FIO2, 20.9%; BP, 530 ± 6 mm Hg) or to NH (FIO2, 14.7%; BP, 720 ± 1 mm Hg). Before and every 8 h during the hypoxic exposures, pulse oxygen saturation (SpO2), HR, and gas exchanges were measured during a 6-min submaximal cycling exercise. At rest, the partial pressure of exhaled NO, blood nitrate and nitrite (NOx), plasma levels of oxidative stress, and pH levels were additionally measured.
During exercise, minute ventilation was lower in HH compared with NH (-13% after 8 h, P < 0.05). End-tidal CO2 pressure was lower (P < 0.01) than PRE both in HH and NH but decreased less in HH than that in NH (-25% vs. -37%, P < 0.05).At rest, exhaled NO and NOx decreased in HH (-46% and -36% after 24 h, respectively, P < 0.05) whereas stable in NH. By contrast, oxidative stress was higher in HH than that in NH after 24 h (P < 0.05). The plasma pH level was stable in HH but increased in NH (P < 0.01). When compared with prenormoxic values, SpO2, HR, oxygen consumption, breathing frequency, and end-tidal O2 pressure showed similar changes in HH and NH.
Lower ventilatory responses to a similar hypoxic stimulus during rest and exercise in HH versus NH were sustained for 24 h and associated with lower plasma pH level, exaggerated oxidative stress, and impaired NO bioavailability.
在短期暴露期间，已经报道了在低气压缺氧（HH）和常压低氧（NH）下休息时，生理反应和一氧化氮（NO）存在细微差异。我们的研究报告了 HH 与 NH 之间在休息时的 NO 和氧化应激以及在中度运动时的生理反应。
10 名受试者随机暴露于 HH（3000 米；FIO2，20.9%；BP，530 ± 6mmHg）或 NH（FIO2，14.7%；BP，720 ± 1mmHg）24 小时。在缺氧暴露前和暴露期间的每 8 小时，在 6 分钟的次最大循环运动期间测量脉搏血氧饱和度（SpO2）、HR 和气体交换。在休息时，还测量了呼气一氧化氮、血液硝酸盐和亚硝酸盐（NOx）、血浆氧化应激水平和 pH 值的部分压力。
在运动期间，与 NH 相比，HH 时分钟通气量较低（8 小时后降低 13%，P < 0.05）。与 PRE 相比，在 HH 和 NH 中，呼气末 CO2 压力均较低（P < 0.01），但在 HH 中下降幅度较小（-25%对-37%，P < 0.05）。在休息时，与 NH 相比，HH 中的呼气一氧化氮和 NOx 降低（24 小时后分别降低 46%和 36%，P < 0.05），而 NH 中的则保持稳定。相反，HH 中的氧化应激比 NH 高（24 小时后，P < 0.05）。HH 中的血浆 pH 值保持稳定，但 NH 中的则增加（P < 0.01）。与预吸氧值相比，在 HH 和 NH 中，SpO2、HR、耗氧量、呼吸频率和呼气末 O2 压力的变化相似。
在 HH 与 NH 之间，休息和运动时对类似缺氧刺激的较低通气反应持续了 24 小时，与较低的血浆 pH 值、氧化应激增加和 NO 生物利用度受损有关。
