Over-hydration and dehydration middle ear resonance effect of frequency and inner ear distortion product otoacoustic emissions: Animal experiment

OBJECTIVE: The most important component of human body is water and its ingredients, and these play a vital role for tissues and cells to function properly. This research attempts to determine the changes by using multi frequency tympanometry (MFT) and distortion product otoacoustic emissions (DPOAE) in middle ear and inner ear acoustic properties of the rats which were exposed to dehydration and over-hydration. METHOD: This research had been conducted on 24 male Sprague Dawey rats. Rats under general anesthesia has gone through otoscopic examination, following that, blood samples of the rats has been taken, their weights have been recorded, middle ear resonance frequency and distortion product otoacoustic emissions of the rats have been measured by using multi-frequency tympanometry and DPOAE. After the procedure, the rats have been divided into three groups: (1) Dehyration group, (2) Over-hydration group, and (3) Control group. The same measurements have been redone after 72 hours. RESULTS: There has been no statistical significance considering weight and osmolarity (p>0,05). Following the body fluid intake (over-hydration)/ dehydration, it has been observed that while both dehydration and over-hydration groups shown a significant change (p<0,05), the control group did not show significance (p>0,05). In addition, the middle ear resonance frequency values of the over-hydration group has been increased significantly (p>0,0003), however, in dehydration and control groups, such changes has not been detected (p>0,05). Similarly, while DPOAE SNR (dB) values of the dehydration and control groups have not shown any significant change, the over-hydration group has shown statistical significance considering the dB changes at 4004 Hz, 7998 Hz, and 9854 Hz frequencies (p<0,05). RESULTS: This study shows that over-hydrating the rats can cause changes in middle ear resonance frequency and DPOAE values of the rats. There should be more studies on how fluid intake affects the middle and inner ear functions. Key Words: Dehydration, over-hydration, osmolarity, middle ear, multi frequency tympanometry, inner ear, otoacoustic emissions This study has been conducted at Baskent University Animal Testing Lab with research ethics committee approval by the Baskent University Animal Experiments Ethical Committee.