Wideband acoustic reflectance and absorbance data in newborns

Description

Objectives: The overall goal of this study was to assess tympanometric and ambient wideband acoustic immittance (WAI) tests and wideband acoustic reflex thresholds (ART) in well-baby and newborn intensive care (NICU) cohorts with three specific objectives: 1) Assess predictive accuracy for WBT and ART for conductive dysfunction in ears referring on the first or second stages of newborn hearing screening; 2) Identify inadequate tests likely due to probe blockages or leaks; and 3) Assess prediction models separately for well-baby and NICU screening outcomes. Design: Prospective, observational study of full-term (n=514) and premature newborns (n=239) recruited from well-baby and NICU nursery birth hospital newborn hearing screening program. Wideband tympanometry, ambient absorbance, and acoustic reflexes were tested after Stage 1 transient otoacoustic emissions (TEOAE) screening. The reference standard for Pass or Refer groups was initially defined on the stage 1 TEOAE test result. Pass or Refer groups were then reassigned based on the stage 2 screening ABR for those who referred at Stage 1, and all NICU infants. Multivariate models were developed using reflectance and admittance variables to predict conductive dysfunction relative to the screening reference standard in a randomized sub-group of subjects at Stage 1 and Stage 2 screening. Classification accuracy was evaluated on a second, independent sub-group. Individual tests were classified as having inadequate probe fits if they had excessively low values of sound pressure level or susceptance (leak) or absorbance (blockage). Results: Differences in ambient absorbance for Pass v. Refer screening groups revealed the greatest differences and effect sizes occurring in frequency bins between 1.4-2 kHz. Screening failure at both Stage 1 and 2 was most accurately predicted by models using ambient absorbance and power level variables at frequencies between 1-2.8 kHz, including ARTs. Tympanometric admittance variables at the positive-pressure tail for frequencies between 1-2.8 kHz in combination with the ART were more accurate predictors than those at peak pressure or the negative-pressure tail. Multivariate models generalized well to an independent group of infants at both Stage 1 and 2 for both the ambient and tympanometric models. Conclusion: Wideband acoustic reflex tests improved all models for ambient and tympanometric absorbance. Multivariate prediction models developed for WAI tests were repeatable in an independent group of well and NICU infants, suggesting that the results are generalizable to these populations. Detection of probe blockage or leaks slightly improved prediction for ambient measures. Pressurized tests have the advantage of ensuring probe seals due to the need for a hermetic seal, thus are useful to ensure adequate probe insertion.  

Steps to reproduce

Wideband acoustic immittance (WAI) data were acquired in human newborn ears using a manufacturer prototype of an ear-canal probe used in the Titan device (Interacoustics, Denmark) and a AT-235 tympanometer (Interacoustics, Denmark) that was modified to allow custom software control of its pump and controller. WAI tests were performed over a frequency range from 0.25 to 8 kHz. The acoustic response to a train of clicks with an inter-click interval of 46 ms and typical total SPL of 69 dB was measured during the pressure sweep in each direction. Silicone disposable probe tips were fit to the probe to provide a hermetic seal for pressurized measurements. The WAI test battery was composed of a downswept tympanometric test, followed by an ambient test, then an upswept tympanometric test, and lastly a wideband acoustic reflex (WB ART) test. The pressure range was +200 daPa to -300 daPa in the downswept tympanogram and was -300 daPa to +200 daPa in the upswept tympanogram. The WB ART was completed last in the test series using sets of five clicks in a pulsed-activator stimulus set, where one click was delivered by the first receiver and four pulsed BBN activators were delivered by the second receiver. The stimulus set was ten activator levels in 5 dB increments ascending in level. Each activator level was specified by the SPL measured in a reference to a 2 cm3 coupler. Data were recorded using custom software running on a personal computer with a two-channel CardDeluxe sound card (22.05 kHz sample rate, 24-bit converters) and RS-232 serial port using custom software. All processing and subsequent analyses of WAI test data described below were performed using MATLAB (version R2022a. Responses were analyzed in terms of absorbance and group delay (i.e., the negative phase gradient measured in units of time across frequency). WB test variables calculated from the WB sound pressure measurement at the probe tip included absorbance (A), group delay (D), complex admittance [any of magnitude (YM), phase (YP), conductance or real part (YR), susceptance or imaginary part (YI), sound pressure level (SPL), and absorbed power level (WL)]. The unit of each of the admittance variables YM, YR and YI was the acoustic mmho (CGS), and the unit of YP was degrees. The unit for absorbed (root mean-squared) power level (WL) was defined as WL=0 dB for a sinusoidal tone with SPL=0 dB acting on a conductance of 1 mmho (CGS). Responses were averaged into eleven half-octave frequency bins to reduce the data to a manageable number of points to be analyzed between 0.25 and 8 kHz.

Institutions

• Cincinnati Children's Hospital Medical Center

  Ohio, Cincinnati

Categories

Funders

• National Institutes of Health

  United States Department of Health and Human Services

  Bethesda

  Grant ID: R01DC010202

Licence