Acute mountain sickness is not related to cerebral blood flow:: a decompression chamber study

To evaluate the pathogenetic role of cerebral blood flow (CBF) changes occurring before and during the development of acute mountain sickness (AMS), peak mean middle cerebral artery flow velocities ((V) over bar(MCA)) were assessed by transcranial Doppler sonography in 10 subjects at 490-m altitude, and during three 12-min periods immediately (SA(1)), 3 (SA(2)), and 6 (SA(3))h after decompression to a simulated altitude of 4,559 m. AMS cerebral scores increased from 0.16 +/- 0.14 at baseline to 0.44 +/- 0.31 at SA(1), 1.11 +/- 0.88 at SA(2) (P < 0.05), and 1.43 +/- 1.03 at SA(3) (P < 0.01); correspondingly, three, seven, and eight subjects had AMS. Absolute and relative (V) over bar(MCA) at simulated altitude, expressed as percentages of low-altitude values (%(V) over bar(MCA)), did not correlate with AMS cerebral scores. Average %(V) over bar(MCA) remained unchanged, because %(V) over bar(MCA) increased in three and remained unchanged or decreased in seven subjects at SA(2) and SA(3). These results suggest that CBF is not important in the pathogenesis of AMS and shows substantial interindividual differences during the first hours at simulated altitude.