Ventilation tube non-function due to blockage in children: the frequency, course and effect on hearing. A prospective cohort study.

OBJECTIVE: To assess the effect on hearing of non-functioning ventilation tubes due to blockage during the first six months post-operatively, using UK national guidelines. METHOD: A prospective, observational study was conducted on 37 children who underwent bilateral ventilation tube insertion. Air and bone conduction thresholds were measured before and following surgery, and at one, three and six months post-operatively. Tube non-function was assessed by tympanometry supported by otoscopy. RESULTS: Post-operatively, an average of 21 per cent of ventilation tubes were non-functioning. Ears with non-functioning tubes had significantly (p = 0.0001) poorer mean air conduction thresholds than functioning tubes, with a magnitude of 6 dB HL. Ears with otorrhoea were most affected (15 per cent). At any one visit, the air-bone gap was closed to 10 dB or less in 76 per cent of ears. Non-functioning tubes reduced this to 56 per cent. Compared with tympanometry, otoscopy underdiagnosed tube non-function due to blockage by 22 per cent. CONCLUSION: Non-functioning of ventilation tubes occurs frequently and can be missed on otoscopy. Although it is associated with poorer air conduction thresholds, the magnitude of this difference is unlikely to warrant further intervention unless there is otorrhoea or recurrence of bilateral hearing impairment.