Abstract
Objective
The aim of this study was to measure DPOAEs in climbers on Mount Everest as a criterion for differential diagnosis of high altitude disease. The levels of distortion product otoacoustic emissions (DPOAEs) change at frequencies between 0,75 kHz and 1,5 kH along with intracranial pressure (ICP). DPOAEs are suggested for monitoring ICP changes.
Methods
In order to determine the etiology of DPOAE-level changes obtained in 6 climbers with severe acute mountain sickness, blood oxygen saturation was measured simultaneously, and a standard request form of Lake-Louis symptoms of high altitude disease was filled in with every DPOAE measurement. Data are presented from DPOAE measurements at frequencies of 1, 1.5, 2, 3 and 4 kHz during an ascent to Mount Everest (8848 m) up to an altitude of 7800 m.
Results
In all climbers, DPOA levels decreased at 4 kHz and 3 kHz with declining oxygen saturation (SaO2) at high altitude. That has been described in many prior animal studies. On the other hand, DPOAE at 1 kHz showed decreasing levels only with symptoms of high altitude disease (AMS). In one climber with severe symptoms of intracranial hypertension after the ascent to the high camp at 7800 m, decreasing DPOAE levels at 1 kHz were measured in the absence of declining blood oxygen saturation. The most pronounced decline of DPOAEs at 1 kHz was also seen on that occasion.
Conclusions
DPOAEs are suggested for detection of intracranial hypertension and early detection of high-altitude cerebral edema.
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