Sanborn Matthew R, Edsell Mark E, Kim Meeri N, Mesquita Rickson, Putt Mary E, Imray Chris, Yow Heng, Wilson Mark H, Yodh Arjun G, Grocott Mike, Martin Daniel S
UCL Centre for Altitude, Space and Extreme Environment Medicine, Portex Unit, Institute of Child Health (Drs Sanborn, Edsell, Imray, Yow, Wilson, Grocott, and Martin), and; Maine Medical Center, Portland, ME (Dr Sanborn).
UCL Centre for Altitude, Space and Extreme Environment Medicine, Portex Unit, Institute of Child Health (Drs Sanborn, Edsell, Imray, Yow, Wilson, Grocott, and Martin), and; St. George's Hospital (Dr Edsell), London, UK.
Wilderness Environ Med. 2015 Jun;26(2):133-41. doi: 10.1016/j.wem.2014.10.001. Epub 2015 Mar 18.
Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy.
Peripheral (Spo2) and cerebral (Scto2) oxygenation, end-tidal carbon dioxide (ETCO2), and cerebral hemodynamics were studied in 12 subjects using transcranial Doppler and diffuse correlation spectroscopy (DCS) at 75 m and then 2 days and 7 days after ascending to 4559 m above sea level. After obtaining baseline measurements, subjects hyperventilated to reduce baseline ETCO2 by 50%, and a further set of measurements were obtained.
Cerebral oxygenation and peripheral oxygenation showed a divergent response, with cerebral oxygenation decreasing at day 2 and decreasing further at day 7 at altitude, whereas peripheral oxygenation decreased on day 2 before partially rebounding on day 7. Cerebral oxygenation decreased after hyperventilation at sea level (Scto2 from 68.8% to 63.5%; P<.001), increased after hyperventilation after 2 days at altitude (Scto2 from 65.6% to 69.9%; P=.001), and did not change after hyperventilation after 7 days at altitude (Scto2 from 62.2% to 63.3%; P=.35).
An intensification of the normal cerebral hypocapnic vasoconstrictive response occurred after partial acclimatization in the setting of divergent peripheral and cerebral oxygenation. This may help explain why hyperventilation fails to improve cerebral oxygenation after partial acclimatization as it does after initial ascent. The use of DCS is feasible at altitude and provides a direct measure of CBF indices with high temporal resolution.
脑血流量（CBF）和脑氧合的改变与高原相关疾病有关。我们使用近红外光谱、经颅多普勒超声和扩散相关光谱技术相结合的方法，评估了在部分适应和过度通气的情况下，海拔上升引起的CBF以及外周和脑氧合的动态变化。
对12名受试者在海拔75米处，以及上升到海拔4559米后的第2天和第7天，使用经颅多普勒和扩散相关光谱技术（DCS）研究外周（Spo2）和脑（Scto2）氧合、呼气末二氧化碳（ETCO2）和脑血流动力学。在获得基线测量值后，受试者进行过度通气以使基线ETCO2降低50%，然后再进行一组测量。
脑氧合和外周氧合表现出不同的反应，在海拔高度时，脑氧合在第2天下降，第7天进一步下降，而外周氧合在第2天下降，然后在第7天部分反弹。在海平面进行过度通气后脑氧合下降（Scto2从68.8%降至63.5%；P<0.001），在海拔2天后进行过度通气后脑氧合增加（Scto2从65.6%升至69.9%；P=0.001），在海拔7天后进行过度通气后脑氧合没有变化（Scto2从62.2%升至63.3%；P=0.35）。
在部分适应且外周和脑氧合不同的情况下，正常的脑低碳酸血症性血管收缩反应增强。这可能有助于解释为什么在部分适应后，过度通气不能像最初上升后那样改善脑氧合。在海拔高度使用DCS是可行的，并且能够以高时间分辨率直接测量CBF指数。
