Emission of high intensity sound is dangerous to the cochlea and can result in noise induced hearing loss (NIHL). Removal of middle ear fluid is common in everyday practice and the possibility of inducing NIHL is seldom considered and not much is known about immission levels. In this study the authors measured sound intensity levels delivered to the ear in the use of suction to remove middle ear fluid. The subjects of the study were children of age six months to six years and sound intensity was measured with a microphone probe attached to the suction tip. The maximum peak intensity ranged from 84 to 157 dB SPL. Half the number of ears were exposed to greater than 140 dB of which 80% were exposed for more than 0.2msec. This is above pain threshold and considered detrimental in terms of NIHL. Higher intensities and duration of suction were recorded for evacuation of mucoid fluid. Suction of serous fluid and empty middle ear caused much less noise exposure in terms of duration and intensity. Interesting literature is discussed examining a direct correlation between the contributions of calibre of the suction tube and lack of finger closure. Most studies recorded lower intensities which can be attributed to less efficient technology in the past and possibly less awareness of this phenomenon. One study demonstrated temporary threshold shift of 15dB or greater. This however, has not been measured in this study but the authors are aware of its significance. This interesting study should be further explored and perhaps mentioned in any consent.

Measurement of sound intensity during suction of middle-ear fluid following myringotomy.
Wang, JC, Allen SJ, Rodriguez AI, et al.
THE JOURNAL OF LARYNGOLOGY & OTOLOGY
2014;128(7):604-11.
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Madhup K Chaurasia

United Lincolnshire Hospitals NHS Trust; University of Leicester, UK.

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