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High-Frequency Distortion-Product Otoacoustic Emission Repeatability in a Patient Population
Laura Dreisbach1, Erika Zettner1, Margaret Chang Liu1
1School of Speech, Language, and Hearing Sciences, San Diego State University, San Diego, California, USA.
Objectives:
Distortion-product otoacoustic emissions (DPOAEs) are repeatable over time at lower frequencies (≤8 kHz) and higher frequencies (>8 kHz) in healthy, normal-hearing subjects. The purpose of this study was to examine the repeatability of DPOAEs measured with high-frequency (HF) stimuli in a patient population. It was hypothesized that HF DPOAEs would be repeatable over four trials.
Design:
DPOAEs were measured in 40 cystic fibrosis (CF) patients (17 females and 23 males) with measurable behavioral thresholds and present DPOAEs for at least 2 of the high frequencies tested (8 to 16 kHz). A depth-compensated simulator sound pressure level (SPL) method of calibration was utilized. Each patient attended four trials, in which a complete set of data were collected. At each trial, three different DPOAE paradigms were completed. First, a discrete frequency sweep was measured between 8 and 16 kHz with a ratio (f2/f1) of 1.2 and levels of 65/50 dB SPL for L1/L2. Next, ratio and level sweeps were obtained at the two highest frequencies with a present DPOAE determined from the discrete frequency sweep, and the results were used to calculate DPOAE group delay and DPOAE detection thresholds, respectively. Ratio sweeps were collected with f2/f1 varied from 1.1 to 1.3 and stimulus levels of 60/45 dB SPL (L1/L2). Level sweeps were collected with an f2/f1 of 1.22 and L2 = 50 and L1 varied between 20 and 70 dB SPL. Differences and correlations between trials, SE of the measurement, and confidence intervals were calculated, as well as a repeated-measures analysis of variance.
Results:
DPOAE response and behavioral threshold variability in CF patients were not significantly different across four trials. It can be expected in 95% of CF patients that differences between trials of DPOAE levels, group delay, and detection thresholds and behavioral thresholds are less than 6.26 dB, 0.87 msec, 9.34 dB, and 9.60 dB, respectively.
Conclusions:
HF DPOAEs were repeatable across four test trials for all three paradigms measured in a group of CF patients. These results are encouraging for the measurement of HF DPOAEs to be monitored in those exposed to ototoxic agents.
