Prognostic Value of Cerebral near Infrared Spectroscopy and Cerebral Blood Flow Velocity for Developing Acute Mountain Sickness at High Altitudes

Using near infrared (NIR) spectroscopy and transcranial Doppler sonography (TCD), we investigated the effects of high altitude in a group of 17 healthy volunteers (mean age ± standard deviation: 46.1 ± 13.1 years) during a common trekking tour in the Nepal Himalayas, lasting 22 days (2850 m to 5600 m). Values of regional cerebral oxygen saturation (rSO₂) obtained by an INVOS 5100 system significantly decreased (p < 0.001) compared to baseline (130 m) at an altitude of 4450 m. Mean blood flow velocity (v _m ) in the middle cerebral artery measured by a portable Smart Dop equipment significantly increased (p < 0.05) compared to baseline (130 m) also at an altitude of 4450 m. The results showed further that all three subjects who developed acute mountain sickness (AMS) and who were not able to continue the trek up to 5050 m, had rSO₂ or v _m values out of the normal range at baseline measurements 130 m above sea level 53 days before starting the tour. Simultaneous measurement of cerebral rSO₂ and v _m parameters could be able to enhance the prognostic accuracy for the development of AMS in the mountain trekking population.