Original contributionA prospective multicenter trial testing the SCOTI device for confirmation of endotracheal tube placement1
Introduction
The Sonomatic Confirmation of Tracheal Intubation (SCOTI) device (Figure 1 ) is a handheld, battery-operated intubation monitor that was invented in 1993 to decrease mortality resulting from accidental esophageal intubation. SCOTI is a third-generation esophageal detection device (EDD). Like previous EDDs, it detects the difference in air content between the flaccid, thin-walled esophagus and the rigid, cartilaginous trachea. Therefore, it does not require a ventilatory trial to provide a reading, nor does it rely on exhaled carbon dioxide, making it potentially useful for patients in cardiac arrest. It has previously been found to be accurate and safe in five small, human studies of surgical patients undergoing elective procedures (Table 1 ; References 1, 2, 3, 4, 5).
After being attached to an endotracheal tube, SCOTI functions by monitoring the state of the tube tip. Feedback is provided in three forms: an audible tone, a variable three-color light-emitting diode (LED), and a numeric liquid crystal display (LCD). During laryngoscopy, such feedback is in real-time, so tube placement confirmation is instantaneous.
Of the three monitors, the LCD is primary because the values it generates are the basis for the audio and LED displays. Liquid crystal display feedback is continuously variable, giving integer numbers that range from 0 to 99. Numbers falling at the extremes of the range trigger dichotomous signals in the audio and LED monitors that correspond to open or closed tube states. Thus, a numerical value of 0, the lowest possible LCD readout, represents an absolute closed state and is accompanied by a red LED and beeping, low-pitched audio tone. A value of 71, the highest LCD readout obtained experimentally, represents an absolute open state and is accompanied by a green LED and a steady, high-pitched tone. The color LED and audio feedback signal serve to simplify and reinforce readings from the LCD monitor.
For LCD values falling between extremes, determination of tracheal or esophageal placement requires an understanding of the SCOTI algorithm used to generate readings. If an LCD value is greater than 16, placement is deemed to be tracheal. This value is 85% of 20, the minimal value accepted by the SCOTI microprocessor for an open endotracheal tube prior to laryngoscopy. (During SCOTI setup, if an open tube initially “tests” less than 20, the microprocessor shuts itself off to prevent false readings.) The 85% value compensates for a decrease in open values observed during prior experiments when a tube is moved from open air into the more acoustically restrictive space enclosed by the larynx or trachea.
For LCD values of 16 or fewer, esophageal placement is considered but must be distinguished from internal occlusion of the tube with secretions. On first encountering an occlusive reading, this involves slight withdrawal of the tube tip into the space previously returning open readings. If SCOTI fails to return an open reading on withdrawal to a previously open space, then tube occlusion is internal rather than external.
Traditional endotracheal tube placement confirmation requires cessation of laryngoscopy, a trial of ventilation for CO2 and oxygen saturation monitoring, auscultation, and other postprocedure confirmation techniques. With SCOTI, placement of an endotracheal tube can be determined during intubation. Endotracheal placement also can be performed blindly during difficult intubations.
In the case of esophageal intubation, repositioning can occur rapidly and without insufflation of the stomach.
Section snippets
Materials and methods
Four emergency departments (EDs) and one surgical department participated in this multi-center trial of the SCOTI device. The study was conducted in two phases. In the first, a convenience sample of consenting elective surgical patients (Hospital San Juan de Diós, Costa Rica) underwent intentional esophageal and tracheal intubations, with SCOTI data recorded for each. Study design included intentional esophageal intubations to increase the validity of specificity calculations; a literature
Results
Data were obtained for 323 intubations using the SCOTI device. Of these, 220 (68%) were tracheal intubations and 103 (32%) were esophageal intubations. Emergency cases numbered 137 (42%), and elective surgical cases 186 (58%). Summary patient and case characteristics are listed in Table 2.
The mean SCOTI reading for esophageal intubation was 5 (SD 6, range 0–40) and for tracheal intubation was 31 (SD 11, range 0–65). Test readings averaged 42 (SD 11, range 21–71). SCOTI correctly identified 205
Discussion
Accidental esophageal intubation is a main cause of morbidity during intubation of the emergency patient. The rate of inadvertent esophageal intubation has been reported in a prospective series of 233 emergency intubations as 3% when rapid-sequence techniques were used versus 18% when not used (12). In an earlier prospective trial of 297 hospitalized patients undergoing emergency intubation by methods of both rapid-sequence intubation and intubation minus paralysis, accidental esophageal
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For the SCOTI Working Group. SCOTI participants are as follows. Massachusetts: Mount Auburn Hospital (coordinating center; James Li, MD, principal investigator). San Jose, Costa Rica: Hospital San Juan de Diós (Wilson León, MD). Missouri: St. John’s Regional Health Center (Alan Clark, MD; Tom Steele, DO; and Charles Sheppard, MD). Ohio: Akron General Medical Center (Lynn White, MS and Joseph Cooper, DO). New York: The Brooklyn Hospital Center (Phil McPherson, MD and Barry Brenner, MD).