Abstract
In order to determine if there is a relation between auditory threshold and oxygen availability, cats were anesthetized, paralyzed and ventilated with room air and with hypoxic gas mixtures. Auditory nerve-brain stem evoked response (ABR) thresholds and arterial blood oxygen levels [partial pressures (PaO2) and percent saturation (SaO2)] were determined. The ABR threshold was unchanged as long as PaO2 was above 30 mm Hg (SaO2 > 45%). Below PaO2 20 mmHg (SaO2 < 25%) the animal was not viable. Between these values, the hypoxia caused ABR threshold elevations which were reversible when the animal was again respirated with room air. ABR threshold was an inverse function of blood O2 level with an approximate 3.05 dB elevation for every mmHg decrease in PaO2 (2.89 dB/% SaO2). These findings are probably due to hypoxia induced depression of the endocochlear potential. Since ABR could be recorded in premature human neonates after at least 28 weeks gestation and since the human fetus in utero is also hypoxic, these results indicate that the fetus (> 28 weeks gestational age) has a sensorineural hearing loss in addition to a conductive loss.
Original language | English |
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Pages (from-to) | 87-91 |
Number of pages | 5 |
Journal | Hearing Research |
Volume | 40 |
Issue number | 1-2 |
DOIs | |
State | Published - 15 Jun 1989 |
Keywords
- Auditory nerve brain stem response
- Endocochlear potential
- Hearing loss
- Hypoxia
- Threshold