Effect of vibration on auditory organ systems in low-birth weight infants treated with high-frequency oscillatory ventilation: 5 year outcome

Background: To determine the effects of vibration exposure caused by high-f requency oscillatory ventilation (HFOV) on the auditory organ systems in lo w-birth weight (LBW) infants. Methods: Between 1989 and 1990, 30 LBW infants who received assisted ventil ation with HFOV (n=14) or conventional mechanical ventilation (CMV; n=16) i n the level III neonatal intensive care unit at Tokyo Metropolitan Ohtsuka Hospital were enrolled in this study. The effects of vibration exposure on the auditory system structures were investigated with auditory brainstem re sponses (ABR) at 37-41 weeks of post-conceptional age and at 6, 12, 18 and 24 months of age until they passed and follow-up studies were performed at least until 5 years of age. Results: All infants enrolled in the study survived at discharge and one (7 .1%) infant in the HFOV group and two (12.5%) in the CMV group failed the i nitial ABR test, but there were no significant differences between the two groups. Auditory brainstem response abnormalities were still observed in on e infant in the HFOV group at 6 months of age, but this child died at 9 mon ths of age because of meningitis. In contrast, in the CMV group, one patien t passed the ABR test at 6 months of age, but another remained abnormal at 5 years of age. One of three infants with ABR abnormalities at 6 months of age had neurologic sequelae at 5 years of age and one of 28 infants who pas sed the initial ABR test was detected with cerebral palsy. No patients with hearing loss were clinically detected at 5 years of age. Conclusions: The results of the serial ABR examinations and the 5 year foll ow-up studies suggest that vibration exposure caused by HFOV may not increa se the adverse effects on the auditory system in LBW infants.