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 occu rring before and during the development of acute mountain sickness (AMS), p eak mean middle cerebral artery flow velocities ((V) over bar(MCA)) were as sessed 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 s cores 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); co rrespondingly, three, seven, and eight subjects had AMS. Absolute and relat ive (V) over bar(MCA) at simulated altitude, expressed as percentages of lo w-altitude values (%(V) over bar(MCA)), did not correlate with AMS cerebral scores. Average %(V) over bar(MCA) remained unchanged, because %(V) over b ar(MCA) increased in three and remained unchanged or decreased in seven sub jects at SA(2) and SA(3). These results suggest that CBF is not important i n the pathogenesis of AMS and shows substantial interindividual differences during the first hours at simulated altitude.