ESOPHAGEAL STETHOSCOPE PLACEMENT DEPTH - ITS EFFECT ON HEART AND LUNGSOUND MONITORING DURING GENERAL-ANESTHESIA

Although the esophageal stethoscope has been used for many years, the effect of the depth of placement on the quality of the sounds obtained has never been investigated. The amplitude and frequency characterist ics of the first and second heart sound and of inspiratory and expirat ory breath sounds were determined at various stethoscope depths (from the distal tip) in 17 healthy anesthetized adults. The amplitude for e ach type of sound varied markedly with depth. Maximal amplitude for S1 was at 34 +/- 3 cm, for S2 at 27 +/- 2 cm, for inspiratory breath sou nd at 28 2 cm, and for expiratory breath sound at 26 +/- 2 cm. There w as a positive linear correlation between the depth of maximal amplitud e of these sounds and patient height. Peak frequency, in general, did not change with depth. We conclude that investigators should measure a nd document depth when performing studies involving the esophageal ste thoscope. Implications: Analysis of sound from the esophageal stethosc ope at various depths reveals that placement depth greatly affects the sounds. A depth of 28-32 cm is recommended for clinical use; S1, S2, and inspiratory and expiratory sounds have a high amplitude in that ra nge.