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[Cochlear and vestibular risk at high altitude]
1Klinik und Poliklinik für Hals-, Nasen- und Ohrenkranke, Ludwig-Maximilians-Universität München. klaus.mees@hno.med.uni-muenchen.de
Laryngo- Rhino- Otologie
|August 13, 2002
Summary
High altitude exposure causes physiological changes impacting the central nervous system, affecting hearing and balance. However, inner ear sensory cells remain unaffected by hypoxia or increased hematocrit.
Area of Science:
- Physiology
- Neuroscience
- Otolaryngology
Background:
- High altitude exposure induces physiological adaptations like hyperventilation and increased oxygen transport capacity via plasma diuresis.
- Hemoconcentration, while increasing oxygen uptake, elevates blood viscosity, serum osmolality, and can impair blood flow.
Purpose of the Study:
- To investigate the effects of high altitude conditions on central nervous system functions, specifically hearing and postural control.
- To determine if cochlear and vestibular sensory cells are impaired by acute hypoxia, elevated hematocrit, or changes in serum osmolality.
Main Methods:
- Utilized hypobaric chamber studies and existing data to analyze physiological responses to lowered oxygen pressure.
- Assessed central nervous system functions including speech discrimination, directional hearing, and postural control.
- Examined the impact of hematocrit levels and serum osmolality on cochlear and vestibular sensory cell function.
Main Results:
- Elevated hematocrit levels and hypoxemia at high altitude may impair central nervous system functions, leading to deficits in speech discrimination, directional hearing, and postural control.
- No evidence suggests that cochlear and vestibular sensory cells are affected by acute hypoxia or hematocrit levels up to 58%.
- Increased serum osmolality or impaired osmoregulation did not interfere with outer hair cell function, preventing threshold shifts and hearing loss.
Conclusions:
- High altitude exposure impacts central nervous system functions related to sensory perception and motor control.
- The inner ear's sensory cells (cochlear and vestibular) demonstrate resilience to the physiological stressors of acute hypoxia and hemoconcentration.