The effect of hypoxia on hearing function

Abstract

Background/aim: This study was conducted to determine the critical partial oxygen pressure (pO2) value that would impair hearing function by evaluating the effects of hypoxia on hearing function in subjects diagnosed with chronic obstructive pulmonary disease (CPOD). Materials and methods: The study included 25 male and 5 female patients referred to our clinic who were diagnosed with COPD, according to spirometry and PaO 2 values, and who did not show pathology upon autoscopic examination. The control group consisted of 14 female and 16 male patients who had no lung disease and were in the same age range as the COPD group. Results: A statistically significant difference was found between the two groups for distortion-product otoacoustic emission (DPOAE) (P < 0.001). The COPD group was divided into two groups according to pO 2 levels (pO 2 ≤ 70 and pO 2 > 70) in order to find a critical pO 2 level which might cause significant change at a certain audiological extent. Conclusion: Hypoxia causes long-term decline in hearing thresholds, deterioration of DPOAE results, and prolongation of I-V interpeak latency in auditory brainstem response. However, the critical oxygen level that disrupts hearing function could not be determined.

Effects of acute hypoxia on auditory pathway of Wistar albino rats

“…It is thought that reactive oxygen products, which are produced during ischemic reperfusion periods, cause cochlear damage. In addition, the magnitude of this damage depends on the length and severity of the ischemic period [1,10,11].…”

“…Ischemia is insufficient blood flow to provide adequate oxygenation that leads to tissue hypoxia or anoxia. Ischemia always results in hypoxia; however, hypoxia can occur without ischemia [1,2].…”

“…The labyrinthine artery is a terminal artery for the cochlear blood supply. The cochlea is highly dependent on the blood and oxygen supply to maintain its function [1,3]. Therefore, it is very sensitive to hypoxia.…”

“…The reduction of hearing sensitivity under acute hypoxia has been attributed to the metabolic sensitivity of various electrochemical potentials in the inner ear [1,6]. These potentials can be formed by metabolically active Na/K ions, and a decrease in oxygen is thought to slow down this process.…”

“…The destructive effect of hypoxia on the cochlea occurs by the reactive products of oxygen formed during the reperfusion period. Reactive oxygen products formed in the event of average oxidative stress can be compensated for by an increase in the synthesis of the antioxidant defense system [1]. In the case of severe oxidative stress, cochlear damage is inevitable because of cell death and the destruction of carbohydrates, proteins, lipids, and nucleic acids [1,7].…”