This Article Full Text (PDF) Submit a scholarly reply Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Raphael, D. T. Articles by Nasseri, B. Search for Related Content PubMed Articles by Raphael, D. T. Articles by Nasseri, B.

ACOUSTIC REFLECTOMETRY CHARACTERIZATION OF 200 ADULT INTUBATIONS

David T. Raphael, M.D., Ph.D.^*, Maxim Benbassat, M.D., Dimiter Arnaudov, M.D., Alex Bohorquez, M.D. and Bita Nasseri, M.D.

^* Associate Professor of Anesthesiology,
Assistant Professor of Anesthesiology,
Resident; Department of Anesthesiology, Keck School of Medicine, University of Southern California, Los Angeles, CA. 90033

INTRODUCTION

Acoustic reflectometry (AR) allows the construction of a 'one-dimensional' image' of a cavity, such as the airway or the esophagus. For an intubated patient, the reflectometric area-distance profile consists of a constant cross-sectional area segment (length of endotracheal tube), followed either by a rapid rise in the area beyond the carina (endotracheal intubation) or by an immediate decrease in the area (esophageal intubation).

METHODS

With Institutional Review Board approval, two hundred (N = 200) adult patients were induced and intubated, without restrictions on the anesthetic agents or airway adjunct devices used. A two-microphone acoustic reflectometer was used to determine whether the breathing tube was placed in the trachea or esophagus. A blinded reflectometer operator, seated a distance away from the patient, used the acoustic area-distance profile only to decide where the tube was placed. End-tidal capnography was used as the 'gold standard'.

RESULTS

Out of 200 tracheal intubations confirmed by capnography, the reflectometer operator correctly identified 198 correctly (99 % correct tracheal intubation identification rate). Two patients were false positives, i.e., patients with a tracheal intubation interpreted as an esophageal intubation. A total of fourteen (14) esophageal intubations resulted, all correctly identified by reflectometry, for a 100 % esophageal intubation identification rate. In twenty patients, the time for the reflectometer operator to reach a cognitive decision as to correct tube placement was measured: for reflectometry, 1.60 ± 0.39 sec; for capnography, 9.65 ± 1.76 sec, after three successive CO₂ waveforms.

DISCUSSION

Acoustic reflectometry is a rapid, non-invasive method by which to determine whether breathing tube placement is correct (tracheal) or incorrect (esophageal). Reflectometry determination of tube placement may be useful in cases where visualization of the glottic area is not possible and capnography may fail, as in cardiac arrest patients. Acoustic reflectometry may also have a more general use as an imaging device in the diagnosis and treatment of airway emergencies.

REFERENCES

1 Jackson AC, Butler JP, Miller EJ, Hoppin FG, Dawson SV. Airway geometry by analysis of acoustic pulse response measurements. J Appl Physiol 1977; 43:523–36.[Abstract/Free Full Text]

2 Raphael DT. Acoustic reflectometry profiles of endotracheal and esophageal intubation. Anesthesiology 2000; 92(5): 1293–1299.[Medline]

This Article Full Text (PDF) Submit a scholarly reply Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Raphael, D. T. Articles by Nasseri, B. Search for Related Content PubMed Articles by Raphael, D. T. Articles by Nasseri, B.