Auscultation in flight: comparison of amplified and traditional stethoscopes

Introduction

Many air medical transport programs use pulse oximeters, end-tidal carbon dioxide monitors and other devices as indirect measures of respiratory and cardiac status. Thus, these methods do not replace cardiac auscultation during flight, which may be needed to identify sudden critical change. And the ability to compare left-sided and right-sided breath sounds may be essential to confirm the appropriate placement of endotracheal tubes as well as to diagnose pneumothorax. The ability for auscultation during air medical transport is compromised by high ambient noise levels. The aim of this study was to assess the capabilities of a traditional and an amplified stethoscope (which is expected to reduce background and ambient noise) to assess heart and breath sounds during medical transport in a FALCON 50 plane.

Methods

A prospective, double-blind, randomized study was performed. We tested one model of traditional stethoscope (Littman^® cardiology III) and one model of amplified stethoscope (Littman 3100). The sound level was amplified in six of the eight increments of the amplified stethoscope. Practitioners on board were all experienced in air medical transport. They had normal audiologic testing. We studied 18 heart and lung auscultations, during real medical evacuations on board the Falcon 50 (medically configured; Dassault aviation). For each, the quality of auscultation was described using a numeric rating scale (ranging from 0 to 10, 0 corresponding to 'I hear nothing', 10 to 'I hear perfectly'). Comparisons were accomplished using a t test for paired values.

Results

Age of patients was 42 ± 11 years, 78% were males. The body mass index was 29.5 ± 4.7. For cardiac auscultation, the value of the rating scale was 5.7 ± 1.4 and 6.5 ± 1.8, respectively, for the traditional and amplified stethoscope (P = 0.027). For lung sounds, quality of auscultation was estimated at 3.6 ± 2.3 for the traditional stethoscope, at 3.9 ± 2.9 for the amplified stethoscope (P = 0.193).

Conclusions

We concluded that flight practitioners in the Falcon 50 are more able to hear cardiac sounds with an amplified than with a traditional stethoscope, whereas there is no significant difference concerning breath sound auscultation. These findings suggested to the investigators that Falcon 50 noise and human breath sounds might share a common or substantially overlapping frequency spectrum, with amplification of one necessarily amplifying the other. To assess this hypothesis, further studies are needed to evaluate the sound frequency spectrum in the medically configured Falcon 50.