Emissões otoacústicas em recém-nascidos com hipóxia perinatal leve e moderada

Abstract

Introduction Severe neonatal hypoxia (as evidenced by the Apgar value) is currently considered the only risk for hearing loss. Hypoxia is one of the most common causes of injury and cell death. The deprivation of oxygen in mild or moderate cases of hypoxia, although smaller, occurs and could cause damage to the auditory system. Objective To investigate the amplitude of otoacoustic emissions in neonates at term with mild to moderate hypoxia and no risk for hearing loss. Methods We evaluated 37 newborns, divided into two groups: a control group of 25 newborns without hypoxia and a study group of 12 newborns with mild to moderate hypoxia. TEOAE and DPOAE were investigated in both groups. Results The differences between groups were statistically significant in the amplitude of DPOAE at the frequencies of 1000, 2800, 4000 and 6000 Hz. In TEOAE, statistically significant differences were found in all tested frequency bands. OAE of the study group were lower than those in the control group. Conclusion Although the occurrence of mild and moderate neonatal hypoxia is not considered a risk factor for hearing loss, deprivation of minimum oxygen during neonatal hypoxia seems to interfere in the functioning of the outer hair cells and, consequently, alter the response level of otoacoustic emissions. Thus, hese children need longitudinal follow-up in order to identify the possible impact of these results on language acquisition and future academic performance.

The effect of hypoxia on hearing function

“…The effect of hypoxia on the cochlea has been attributed to the metabolic alteration of various electrochemical potentials in the ear [12]. These potentials are formed by the metabolic activity of Na/K ions, and it is believed that a decrease in oxygen supply diminishes this process [10].…”

“…Hypoxia affects otoacoustic emissions as it affects hearing thresholds [12,14,16]. In the first 15 min following cochlear ischemia, swelling and deterioration occurred in the external shaky hair cells.…”