Theoretical considerations and experimental evidence suggest that otoacoustic emission parameters may be used to reveal early cochlear damage, even before it can be diagnosed by standard audiometric techniques. In this work, the statistical distributions of a set of otoacoustic emission parameters chosen as candidates for the early detection of cochlear damage (global and band reproducibility, response level, signal-to-noise ratio, spectral latency, and long-lasting otoacoustic emission presence) were analyzed in a population of 138 ears. These ears have been divided, according to a standard audiometric test, in three classes: (1) ears of nonexposed bilaterally normal subjects, (2) normal ears of subjects with unilateral noise-induced high-frequency hearing loss, and (3) their hearing impaired ears. For all analyzed parameters, a statistically significant difference was found between classes 1 and 2. This difference largely exceeds the difference observed between classes 2 and 3. This fact suggests that the noise exposure, which was responsible for the unilateral hearing loss, also caused subclinical damage in the contralateral, audiometrically normal, ear. This is a clear indication that otoacoustic emission techniques may be able to early detect subclinical damages.

The relationship between hearing loss, detected by measuring the audiometric threshold shift, and the presence of long-lasting otoacoustic emissions, has been studied in a population of 66 adult males, by analyzing the cochlear response in the 80 ms following the subministration of a click stimulus. Most long-lasting OAEs are also recognizable as Synchronized Spontaneous OAEs (SSOAEs). The OAE characteristic decay times were evaluated according to the model by Sisto and Moleti [J. Acoust. Soc. Am. 106, 1893 (1999)]. The starting hypothesis, confirmed by the results, is that long decay time and large equilibrium amplitude are both manifestations of the effectiveness of the active feedback mechanism. The prevalence and frequency distribution of long-lasting OAEs, and of their SSOAE subset, have been separately analyzed for normal and impaired ears. No long-lasting OAE was found within the hearing loss frequency range, but several were found in impaired ears outside the hearing loss range, both at lower and higher frequencies. This result suggests that the correlation between the presence of long-lasting OAEs and good cochlear functionality be local in the frequency domain. The monitor of the OAE decay time is proposed as a new possible method for early detecting hearing loss in populations exposed to noise.

No abstract

The aim of the study is to evaluate the Eustachian tube functionality in a group of aviators to underline a subclinical dysfunction and the related risk of ear fullness or barotitis. Hypobaric chamber allows to simulate the pressure variation of the flight. This prospective study enrolled 42 aviation pilots, members of the Italian Air Force, to whom were evaluated Eustachian tube functionality by Tubomanometry, patients subjective assessments concerning feasibility of Valsalva's and Toynbee's clinical symptoms, tympanometry, and objective Valsalva before and after exposure to hypobaric chamber. The new Eustachian tube score (ETS-7) was also calculated for each pilot before and after exposure to hypobaric chamber. Results of our examination showed that: before chamber exposition, in 92.8 % of pilots, an ETS-7 of eight or more was found bilaterally. In three (7.2 %) cases, a unilateral ETS-7 ≤ 7 was found and two of those had a positive history. After undergoing the hypobaric chamber session, the evaluation of ETS-7 showed only 19 % of pilots with an ETD score ≤7, in particular three bilateral and five unilateral cases. Three of those pilots were clinically positive: two airmen reported persistent fullness, while the other one had a barotitis. Therefore, the combined use of TMM and ETS-7 before and after hypobaric chamber exposure appears to be a reliable method for assessing the functional capacity of the Eustachian tube in aviators, the stressful effect of flight on it, to exclude subjects at increased risk of ear pain, fullness, or barotrauma.

This difference between on-vertical and off-vertical axis rotation was probably partly due to the vestibular transfer function and partly due to different adaptation to the speed of rotation. Such a phenomenon might be generated in different components of the vestibular system. The adaptive process enhancing the perception of dynamic movement around the vertical axis is not related to the specific semicircular canals that are activated; the addition of an otolithic component results in a significant increase of the TPE.Panichi R, Occhigrossi C, Ferraresi A, Faralli M, Lucertini M, Pettorossi VE. Adaptive changes in the perception of fast and slow movement at different head positions. Aerosp Med Hum Perform. 2017; 88(5):463-468.