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device was developed, which was sold in Europe by Penlon (Abingdon, Oxon, UK) from April 1995 until 1996 and then was withdrawn. 5Several papers about the SCOTI device were published in Medline-indexed journals, most of which described problems. 6–11Although the algorithm used by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.

Raphael DT: Acoustic reflectometry profiles of endotracheal and esophageal intubation. A nesthesiology 2000; 92: 1293–9
Mansfield JP, Lyle RP, Voorhees WD, Wodicka GR: An acoustical guidance and position monitoring system for endotracheal tubes. IEEE Trans Biomed Eng 1993; 40: 1330–5
Akerson SH: Tracheal intubation monitoring apparatus and method. US patent 5,331,967. July 26, 1994
Riopelle JM, Akerson H, Léon W: Comparison of 2 modes of operation of a new sonometric device designed to rapidly distinguish tracheal from esophageal intubation: A laboratory study using porcine organs (abstract). A nesthesiology 1994; 81: A622
Richardson C: Management of the airway and ventilation during resuscitation (letter). Br J Anaesth 1997; 79: 814
Haridas RP, Chesshire NJ, Rocke DA: An evaluation of the SCOTI device. Anaesthesia 1997; 52: 453–6
Lockey DJ, Woodward W: SCOTI vs. Wee: An assessment of two oesophageal intubation detection devices. Anaesthesia 1997; 52: 242–3
Murray D, Ward ME, Sear JW: SCOTI: A new device for identification of tracheal intubation. Anaesthesia 1995; 50: 1062–4
Nandwani N, Caranza R, Lin ES, Raphael JH: Configuration of the SCOTI device with different tracheal tubes. Anaesthesia 1996; 51: 932–4
Petroianu G, Maleck W, Bergler W, Rüfer R: Sonomatic confirmation of tracheal intubation using the SCOTI. Prehosp Disaster Med 1997; 12: 149–53
Trikha A, Singh C, Rewari V, Arora MK: Evaluation of the SCOTI device for confirming blind nasal intubation. Anaesthesia 1999; 54: 347–9