Physiologic chest sounds and helicopter engine noise.

To develop an amplification system for physiologic chest sounds during air medical transport in jet helicopters, we compared frequency spectra of physiologic chest sounds and Allison C-28 equipped jet helicopter noise. We found that the frequency spectrum of physiologic chest sounds is contained entirely within that of jet rotocraft noise. Attempts to amplify physiologic chest sounds or to filter jet rotorcraft noise will invariably fail to improve perception of chest sounds. Future research must focus on assessment of actual movement of the chest and of each hemithorax, as well as an carbon dioxide production, as indicators of adequate ventilation and proper endotracheal tube position.