Cerebrovascular compliance is not associated with acute mountain sickness following staged ascent to 4300 m (708.3)

Abstract

We hypothesized that a reduction in cerebrovascular compliance (∆V), due to cerebral edema, would be associated with acute mountain sickness (AMS) following staged ascent to 4300 m. Forty‐five unacclimatized men and women (mean±SD; 24±5 yr) were exposed to 48 h at a staging altitude at or above 2500 m followed by 24 h at 4300 m. AMS was assessed using the Environmental Symptoms Questionnaire. Near‐infrared spectroscopy was used to assess ∆V within the right frontal lobe via calculation of change in relative total hemoglobin concentration from resting baseline to peak value during a valsalva maneuver to a fixed pressure. Hemoglobin and hematocrit were measured to calculate changes in plasma volume (PV). All assessments were completed at rest in the morning at sea level (SL) and after 24 hours at 4300 m (HA). AMS severity increased (P<0.001) from SL (0.07±0.15) to HA (0.44±0.43). ∆V also increased (P<0.001) from SL (3.08±0.35) to HA (4.60±0.49). PV decreased (P<0.001) from SL to HA (‐17.3±7.1%). No relationship was found between the change in ∆V from SL to HA and the change in AMS severity (r=0.04;p=0.78), but the change in ∆V was significantly associated with the % change in PV (r=0.34;p=0.01). We conclude that ∆V was not related to AMS, potentially caused by cerebral edema, but rather hemoconcentration following staged ascent to 4300 m. Funding: USAMRMC. Authors’ views not official US Army or DOD policy.Grant Funding Source: Supported by USAMRMC