Effects of flight on auditory function in pilots

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Eugene Boone
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1 Effects of flight on auditory function in pilots ZHANG Yange PhD ZHANG Xia, SUN Xuelei, XIE Sujiang Institute of Aviation Medicine, AF. CHINA

2 Disclosure Information 84 th Annual AsMA Scientific Meeting ZHANG Yange I have no financial relationships to disclose. I will not discuss off-label use and/or investigational use in my presentation

3 Background Military pilots are exposed to cabin noise. Noise induced hearing loss is the most common problem in aviation. The sense of hearing is the most important sense for pilots. Noise induced hearing loss may have implications for safety of aircraft.

4 Hearing may become more important as new technology requires more advanced listening than sentences and simple warning signals. The aim of this study was to investigate hearing loss of pilots and explore effects of flight on auditory function in pilots. The study may be useful in giving advice to military pilots about preventive measure.

5 METHODS Subjects were 116 male military pilots,23-56 yr of age. Their total flying time ranged from hours. The subjects were divided into four groups by age: Group P1, yr (n=61, yr, 354 h); Group P2, yr (n=20, yr, 1866 h); Group P3, yr (n=28, 44.03yr, 2913 h); Group P4, yr (n=7, 52.57yr, h).

6 Pure Tone Audiometry Tympanometry DPOAE Equipments: 2 channel GSI 16 Audiometer. Madsen ZODIAC 901 middle ear analyser. OB282 Otodynamics OAE Systems.

7 % Results 1.Hearing loss of pilots was at Hz % Rat es of NI HL % % % uni l at er a bi l at er al t ot al % 0. 00% P1 P2 P3 P4 Pi l ot Gr oups Fig 1 The Rates of Hearing Loss at high frequencies for pilots

8 2. Mean hearing thresholds for Audiogram for two groups P1 P2 P3 P C1 C2 C3 C Figure.2 Mean thresholds for pilot groups Fig.3 Mean thresholds for control groups.

9 3. Provocation rates of DPOAE Tab Provocation rates of DPOAE

10 Discussion Long-term flight damages auditory function of pilots. The extent of hearing loss depends on exposure loudness, duration and frequency, genetic heredity, gender. Our results suggests that the same exposure loudness and duration can lead to different hearing loss.

11 The prevalence of unilateral hearing loss at high frequencies was higher than that of bilateral hearing for pilots with years. The prevalence of bilateral hearing loss at high frequencies increased with flight time. Similar rates of pilots with 40+ years had unilateral and bilateral hearing loss at high frequencies % of pilots with 50+ years had bilateral hearing loss at high frequencies. The characteristic of hearing loss of current pilots is 6000Hz notched audiogram.

12 Pure tone thresholds were not significantly different between the two groups aged years. Hearing loss occurred at 6kHz in pilots aged 30+ years. Then there were significant threshold shifts at 4kHz and 6kHz in pilots aged 40+ years. For subjects aged years hearing thresolds of pilots significantly elevated at 3kHz,4kHz,6kHz,8kHz. Among control groups aged years, pure tone audiogram was within the normal range. But the hearing threshold of the control group aged years elevated. The audiogram exhibited a ski-slope pattern of loss. It was different from characteristics of audiometry curve of pilot groups. It is characteristics of aging hearing loss.

13 In previous reports, The 4000 Hz notch was considered the sign characteristics of NIHL. The current pilot groups showed 6000 Hz notch. The current result suggests that noise firstly damages 6000Hz, then progressively develop to other frequencies with exposure time.

14 DPOAE are thought to arise from the normal function of outer hair cells(ohc) in the organ of Corti. A wealth of experimental and clinical data confirm that the absense of OAEs relates with the loss of OHC function associated with a decrease in hearing sensitivity. OHC is the target organ of noise, DPOAE firstly reflects NIHL. The result suggests that DPOAE provocation rates of pilots were lower than that of control groups at 3000Hz, 4000Hz, 6000Hz. DPOAE provocation rates of pilots decreased with flight time even then hearing thresholds were in normal range.

15 It indicates that Cochlear function is firstly damaged at 6000Hz by noise before subjective hearing thresholds don t change. The result of DPOAE coincides with pure tone audiometry. DPOAE can provide an accurate mapping of damaged frequency intervals, and this likely when OHCs are the chief cause of hearing loss. DPOAE is a sensitive measure for monitoring early noise-induced hearing loss. This should prove to be useful for long-term monitoring.

16 In aviation, we should pay more attention to noise of aircraft effects on auditory function in pilots. Monitoring and preventive measurements should be taken as earlier as possible. Finding safe and effective intervention measurement that attenuate NIHL, it is the direction of research in the future.

17 Conclusions Long-term flight damages auditory function of pilots. The prevalence and characteristics of Hearing loss of current pilots is 6000Hz notched audiogram. DPOAE is a sensitive measure for monitoring early noise-induced hearing loss. There is the susceptibility and resistance to noise in human ears.

18 Thank you!

Basic Audiogram Interpretation

Basic Audiogram Interpretation Audiogram - graph showing Frequency on Horizontal axis db Hearing Level on Vertical axis db level increases as we move down on graph Audiogram displays the individuals pure