Abstract
Objective: To study the relationship between changes in the cerebral blood flow (CBF) velocity with symptoms of acute mountain sickness (AMS) during simulated high altitude. Research Design and Methods: Mean middle arterial cerebral flow velocity (MCAv) was assessed by transcranial Doppler sonography in 8 healthy lowland male adults aged 20 - 24 yrs before and after 6 h and 48 h at simulated altitude corresponding to 4572 m. The same study was repeated three weeks later in the same subjects. End-tidal pCO2 (ETCO2) and arterial oxygen saturation (SaO2) were measured by standardized procedures. AMS symptoms were recorded using the modified environmental symptoms questionnaire after 6 h and 48 h exposure to calculate the mean score of cerebral (AMS-C) symptoms. Results: Mean MCAv significantly increased with high altitude (HA) by 4% at 6 h HA and 24% at 48 h HA (P 2 (mean ± SD 32 ± 4 mmHg; r = 0.47, P 2 (77% ± 8%; r = - 0.43, P 2 (r = - 0.55, P
Highlights
Acute mountain sickness (AMS), characterized by headache, dizziness, nausea, breathlessness, fatigue and insomnia, may occur during rapid ascent to altitudes above 2500 m, in humans poorly acclimatized to such extreme conditions
Our results suggest that there is a lack of relationship between changes in cerebral blood flow (CBF) velocity with symptoms of acute mountain sickness (AMS), and that a substantial inter-subject variance exists in the CBF response to high altitude exposure
One of the 10 original volunteers had to leave the study due to clinical symptoms of AMS (AMS-C score 3.4) after a few hours of hypobaric exposure, and data obtained from another subject were excluded for missing a transcranial Doppler (TCD) examination
Summary
Acute mountain sickness (AMS), characterized by headache, dizziness, nausea, breathlessness, fatigue and insomnia, may occur during rapid ascent to altitudes above 2500 m, in humans poorly acclimatized to such extreme conditions. The precise pathophysiology of AMS is not known, on the basis of early findings increased cerebral blood flow (CBF) in the first few hours of high altitude exposure may play an important role in the pathogenesis of AMS (Huang et al, 1987; Lassen, 1992; Baumgartner et al, 1994). Early findings indicate that increased CBF is higher in those with AMS than those without AMS symptoms (Baumgartner et al, 1994), this has not been confirmed in later studies (Baumgartner et al, 1999; Dyer et al, 2008; Lucas et al, 2011). Some authors concluded that CBF is not a relevant factor in the pathogenesis of AMS (Baumgartner et al, 1999)
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