Wideband acoustic immitance – Absorbance measurements in ears after stapes surgery. Issue 6 (December 2020) - Niemczyk, Elżbieta
Abstract: Objectives: The study aimed to thoroughly assess absorbance in ears after stapes surgery (stapedotomy/stapedectomy) and how stapes surgery affects wideband acoustic immittance (WAI) metrics. Methods: Eighty-three otosclerotic ears were analyzed pre- and postoperatively. The analysis comprised: air-bone gap (ABG) and WAI which included absorbance measurements, resonance frequency assessment, low frequency tympanometry and metrics derived from these measures. Results: Absorbance after stapes surgery changed considerably compared to otosclerotic ears before surgery and also differed from normal ears. Absorbance after stapes surgery revealed two significantly different plot types: single-low-frequency-peak absorbance and two-peaks absorbance. Stapes surgery reduced resonance frequency in majority of operated ears and increased static compliance in low frequency tympanometry. Static compliance difference was directly proportional to ABG improvement at low frequencies. Postoperative ABG at 250 Hz and 500 Hz was most commonly correlated with postoperative WAI parameters. ABG improvement at 3000 Hz and 4000 Hz was directly proportional to absorbance difference at ~3000 Hz and 4000 Hz. It influenced the width of the postoperative absorbance by shifting both sides of the plot (negative values shift the points of the plot toward lower frequencies) with the correlation being more pronounced in postoperative two-peaks absorbance type ears. Conclusions: Absorbance by itself is not sufficient for assessment of changes to middle function following stapes surgery, and should be complemented with other measures. WAI measurements including absorbance, resonance frequency assessment, low frequency tympanometry, and metrics derived from these measures combined with air-bone gap provide insight into mechano-acoustic changes in the middle-ear system as a result of stapes surgery.