The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts


Jonathan B. Waugh, PhD; Dale W. Callahan, PhD; Wesley M. Granger, PhD; George A. Mathew, MS. University of Alabama at Birmingham, Birmingham, AL.

BACKGROUND: There are many types of stethoscopes currently marketed but clinicians have little independent data on which to base comparison of models that can vary greatly in design and price. We tested 38 stethoscope models to determine if there was a difference based on analysis of power spectral density (PSD).

METHODS: Thirty-eight different models (categorized as cardiology, physical assessment, basic assessment, and disposable) of adult stethoscopes (all had diaphragm chest pieces, 27 had bell chest pieces) were measured using a pink noise input from 50-3000 Hertz. Four copies of each model were tested and the data averaged for comparison by ANOVA. The area under the curve (AUC) measured from PSD plots of the relative change in decibels (dB) (difference of stethoscope output signal from reference input signal) for each model versus the measured frequency range was compared.

RESULTS: The Tukey-Kramer Multiple-Comparison test indicated no statistical difference (alpha level 0.05) among the 23 models with the lowest AUC averages when using the diaphragm chest pieces (the lower the AUC the less signal loss). There was no statistical difference among the 13 models with the lowest AUC averages when using the bell chest pieces. The diaphragm models that were not statistically different from the smallest AUC value (inclusive) were Allen Medical Instruments Mark 10, Allen Medical Inst. Gemini, Phillips 280-A02, Prestige Model 129, Mabis Caliber Dual Head, Mabis Signature SS, Mabis Crystal Scope, Nursemates Select-a-scope, Prestige Model 112, Ultrascope, Welch Allyn Professional, Omron Mentor II, Littmann Classic SE, ADC Adscope 600, ADC Proscope 670, Littmann Master Cardiology, Mabis Caliber, Littmann Cardiology STC, Prestige Model 126, ADC Adscope 609, Omron Mentor II Cardiology, DRG PureTone Cardiology. The bell models that were not statistically different from the smallest AUC value (inclusive) were Welch Allyn Harvey DLX, Mabis Caliber Dual Head, ADC Proscope 670, Welch Allyn Harvey Elite, Prestige Model 112, Prestige Model 122, Allen Medical Inst. Gemini, Prestige Model 129, Phillips 280-A02, Mabis Signature SS, Allen Medical Mark 10, Nursemates Sprague Rappaport-type, ADC Adscope 601.

DISCUSSION: The results show that the lowest bell and diaphragm AUC values did not occur with the same models of stethoscope. There was a greater range of mean values for the bell chest pieces than with the diaphragms chest pieces.

CONCLUSION: Bench testing using computerized signal processing methods (based on AUC values from PSD plots) shows no statistical differences between many of the models tested. These results need to be compared to testing done with experienced human auscultators to see if these statistical findings correspond to clinical findings.

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