To the Editor:—
I enjoyed the article of Raphael 1that described a new instrument for distinguishing endotracheal and esophageal intubation by acoustic reflectometry. I agree with his conclusion that such a device has a place in emergency airway management because it is independent of carbon dioxide exhalation, it is not subject to operator bias, and it does not necessitate ventilation into a possibly misplaced tube. However, I was surprised that Raphael missed some of the previous literature on this subject.
First, Mansfield et al. , 2who in 1993 were the first to describe this application of acoustic reflectometry, must be mentioned. Second, the related technique of Akerson, 3,4which used resonant sound, was patented in the US, and was presented at the American Society of Anesthesiologists meeting in 1994, should be mentioned. From the Akerson patent, the Sonomatic Confirmation of Tracheal Intubation (SCOTI) device was developed, which was sold in Europe by Penlon (Abingdon, Oxon, UK) from April 1995 until 1996 and then was withdrawn. 5Several papers about the SCOTI device were published in Medline-indexed journals, most of which described problems. 6–11Although the algorithm used by Raphael 1is much more sophisticated than that used by the SCOTI device, each of the problems described with the SCOTI device should be discussed to clarify whether they can be excluded with the device of Raphael.