Comparative Study of Hearing Loss between Using and Not using 5-Wing Type Ear Protection of Thai Military Training Conscripts

Watcharaporn Bourchom MD 1 , Pongthep Hanchumpol 1 , Pariyanan Jaruchinda MD 1

Affiliation : 1 Department of Otorhinolaryngology Phramongkutklao Hospital, Bangkok, Thailand

Background : At present, ear protective devices during gunfire by Thai military training conscripts are not routinely used. The 5-wing type ear protection was invented to protect them from hearing loss with lower cost and better transmitted speaking voice.
Objective : To study the effectiveness of 5-wing type ear protection in shielding sensorineural hearing loss (SNHL) from military shooting training.
Materials and Methods : The study design was a randomized control trial (RCT) study. Sixty conscripts during routine training were enrolled and randomized in 2 groups: not using ear protection and 5-wings type ear protection groups as they routinely trained. Audiogram and Distortion Product Otoacoustic Emission (DPOAE) was performed before and after firing within 24 hr, 3 rd day and 7 th day in both groups.
Result: Immediately after gunfire, those not using ear protection group had SNHL more than the other group at a high frequency (53.2% vs. 0%, p < 0.05). At day 3, the hearing levels were gradually improved at all frequencies except 6,000 Hz. At day 7, three conscripts (10%) in the not using ear protection group still had SNHL detected by audiogram, 12 individuals (40%) had abnormal outer hair cell (OHCs) function detected by DPOAE.
Conclusion : The 5-wing type ear protection could prevent SNHL immediately after gunfire training. DPOAE had higher sensitivity than audiograms in detecting OHCs deficiency up to 30%.

Keywords : Sensory neural hearing loss, Audiogram, DPOAE , 5-wing type ear protection

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