Centre for Altitude, Space and Extreme Environment Medicine (CASE Medicine), University College London Portex Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
Crit Care. 2009;13 Suppl 5(Suppl 5):S7. doi: 10.1186/cc8005. Epub 2009 Nov 30.
We sought to quantify changes in skeletal muscle oxygenation during exercise using near-infrared spectroscopy (NIRS) in healthy volunteers ascending to high altitude.
Using NIRS, skeletal muscle tissue oxygen saturation (StO2) was measured in the vastus lateralis of 24 subjects. Measurements were performed at sea level (SL; 75 m), at 3,500 m, on arrival at 5,300 m (5,300 m-a; days 15 to 17) and at 5,300 m again (5,300 m-b; days 69 to 71). Amongst the subjects, nine remained at 5,300 m whilst 14 climbed to a maximum of 8,848 m. Exercise was 3 minutes of unloaded cycling followed by an incremental ramp protocol to exhaustion. The absolute StO2 at different stages of exercise along with the difference between StO2 at stages and the rate of change in StO2 were compared between altitudes. Resting peripheral oxygen saturation was recorded.
NIRS data achieving predefined quality criteria were available for 18 subjects at 75 m, 16 subjects at 3,500 m, 16 subjects on arrival at 5,300 m and 16 subjects on departure from 5,300 m. At SL, mean StO2 declined from 74.4% at rest to 36.4% at maximal oxygen consumption (P < 0.0001) and then rose to 82.3% (P < 0.0001) 60 seconds after exercise had ceased. At 3,500 m-a and 5,300 m-b, the pattern was similar to SL but absolute values were approximately 15% lower at all stages. At 5,300 m-a, the resting StO2 was similar to SL and the change in StO2 at each exercise stage less marked. At 5,300 m-b, the rate of decline in StO2 during exercise was more rapid than SL (P = 0.008); here the climbers had a smaller decline in StO2 during exercise (41.0%) and a slower rate of desaturation (0.086%/second) than those who had remained at 5,300 m (62.9% and 0.127%/second) (P = 0.031 and P = 0.047, respectively).
In most individuals, NIRS can be used to measure exercising skeletal muscle oxygenation in the field. During exercise the patterns of absolute oxygenation are broadly similar at altitude and SL. Following prolonged adaptation to altitude, the rate of muscle desaturation is more rapid than observed at SL but less so in those exposed to extreme hypoxia above 5,300 m.
我们旨在通过近红外光谱（NIRS）测量健康志愿者在海拔升高过程中的骨骼肌氧合变化。
使用 NIRS 测量 24 名受试者股外侧肌的组织氧饱和度（StO2）。测量在海平面（SL；75m）、海拔 3500m、海拔 5300m 到达时（5300m-a；第 15-17 天）和海拔 5300m 再次（5300m-b；第 69-71 天）进行。在这些受试者中，有 9 人留在 5300m，而有 14 人攀登到 8848m 的最高海拔。运动是 3 分钟的无负荷自行车运动，然后进行递增斜坡至力竭。在不同阶段的运动中，比较 StO2的绝对水平以及阶段之间的 StO2差异和 StO2的变化率。记录休息时外周氧饱和度。
在 75m 处有 18 名受试者、在 3500m 处有 16 名受试者、在 5300m 到达时处有 16 名受试者和在离开 5300m 时处有 16 名受试者获得了满足预定义质量标准的 NIRS 数据。在 SL，StO2 平均值从休息时的 74.4%下降到最大耗氧量时的 36.4%（P<0.0001），然后在运动停止后 60 秒上升到 82.3%（P<0.0001）。在 3500m-a 和 5300m-b，模式与 SL 相似，但在所有阶段的绝对值约低 15%。在 5300m-a，休息时的 StO2与 SL 相似，每个运动阶段的 StO2 变化不那么明显。在 5300m-b，运动时 StO2 的下降速度比 SL 更快（P=0.008）；在这里，登山者在运动期间的 StO2 下降幅度较小（41.0%），饱和度下降速度较慢（0.086%/秒），而那些留在 5300m 的人下降幅度较大（62.9%和 0.127%/秒）（P=0.031 和 P=0.047）。
在大多数人中，NIRS 可用于在现场测量运动中的骨骼肌氧合。在运动过程中，绝对氧合的模式在海拔和 SL 上大致相似。在长时间适应高原后，肌肉饱和度的下降速度比在 SL 时更快，但在海拔 5300m 以上暴露于极端低氧时速度较慢。
