Letters to the Editor
Unusual Expired Carbon Dioxide Waveform To the Editor:
Rep1 y :
1 would like to point out that the unusual expired carbon dioxide (CO,) waveform reported by Drs. Mokriski, Nagle, and Fragneto,’ which was correctly attributed to a leak between the sampling tubing and the connection to the monitor, had been reported previously .2,3 In a complete analysis of the determinants of the shape of this unusual waveform,3 the height of the plateau part of the waveform was determined by the size of the leak, whereas the height of the peak of the waveform was determined by the magnitude of the next tidal inspiration3 1 also would like to point out that the appearance of the expired CO, waveform in a fiber-optically proven mainstem bronchial intubation has recently been reported and is indeed similar to the waveform displayed in the educational material of Hewlett-Packard.4
Dr. Benumof is correct that the waveform we described’ has been noted previously.‘,” Its similarity to the waveform obtained with a mainstem bronchial intubation was not noted in these earlier reports. We submitted our letter to emphasize the similarities between the waveform produced by the leak and the waveform produced by the mainstem bronchial intubation. If a leak is not recognized, an unintentional extubation may ensue. Confirmation of the expired carbon dioxide waveform in a proven mainstem bronchial intubation” was published after submission of our letter. Bettylou K. Mokriski, MD Assistant Professor of Anesthesiology Sheryl E. Nagle, MD Assistant Professor of Anesthesiology
Jonathan L. Benumof, MD Professor of Anesthesia University of California, San Diego San Diego, CA
University of Maryland School of Medicine Baltimore, MD 21201
References
References
1. Mokriski BLK, Nagle SE, Fragneto RY: Does the expired carbon dioxide waveform suggest endobronchial intubation? [Letter]. J Clin Anesth 1990;2: 140-1. 2. Martin L, Zupan J, Benumof JL: Unusual end-tidal CO, waveform. Anesthesiology 1987;66:712-3. 3. Zupan J, Martin L, Benumof JL: End-tidal CO, excretion waveform and error with gas sampling line leak. Anesth Analg 1988;67:579-81. 4. Cilbert D, Benumof JL: Biphasic carbon dioxide elimination waveform with right mainstem bronchial intubation. Anesth Analg 1989;69:829-32.
1. Mokriski BLK, Nagle SE, Fragneto RY: Does the expired carbon dioxide waveform suggest endobronchial intubation? [Letter]. J Clin Anesth 1990;2: 140-1. 2. Martin L, Zupan J, Benumof JL: Unusual end-tidal CO, waveform. Anesthesiology 1987;66:712-3. 3. Zupan J, Martin L, BenumofJL: End-tidal CO, excretion waveform and error with gas sampling line leak. Ane.rth Analg 1988;67:579-81. 4. Gilbert D, Benumof JL: Biphasic carbon dioxide elimination waveform with right mainstem bronchial intubation. Anesth Analg 1989;69:829-32.
80
J. Clin. Anesth.,
vol. 3, JanuaryiFebruary
1991
Unusual Expired Carbon Dioxide Waveform To the Editor:
Rep1 y :
1 would like to point out that the unusual expired carbon dioxide (CO,) waveform reported by Drs. Mokriski, Nagle, and Fragneto,’ which was correctly attributed to a leak between the sampling tubing and the connection to the monitor, had been reported previously .2,3 In a complete analysis of the determinants of the shape of this unusual waveform,3 the height of the plateau part of the waveform was determined by the size of the leak, whereas the height of the peak of the waveform was determined by the magnitude of the next tidal inspiration3 1 also would like to point out that the appearance of the expired CO, waveform in a fiber-optically proven mainstem bronchial intubation has recently been reported and is indeed similar to the waveform displayed in the educational material of Hewlett-Packard.4
Dr. Benumof is correct that the waveform we described’ has been noted previously.‘,” Its similarity to the waveform obtained with a mainstem bronchial intubation was not noted in these earlier reports. We submitted our letter to emphasize the similarities between the waveform produced by the leak and the waveform produced by the mainstem bronchial intubation. If a leak is not recognized, an unintentional extubation may ensue. Confirmation of the expired carbon dioxide waveform in a proven mainstem bronchial intubation” was published after submission of our letter. Bettylou K. Mokriski, MD Assistant Professor of Anesthesiology Sheryl E. Nagle, MD Assistant Professor of Anesthesiology
Jonathan L. Benumof, MD Professor of Anesthesia University of California, San Diego San Diego, CA
University of Maryland School of Medicine Baltimore, MD 21201
References
References
1. Mokriski BLK, Nagle SE, Fragneto RY: Does the expired carbon dioxide waveform suggest endobronchial intubation? [Letter]. J Clin Anesth 1990;2: 140-1. 2. Martin L, Zupan J, Benumof JL: Unusual end-tidal CO, waveform. Anesthesiology 1987;66:712-3. 3. Zupan J, Martin L, Benumof JL: End-tidal CO, excretion waveform and error with gas sampling line leak. Anesth Analg 1988;67:579-81. 4. Cilbert D, Benumof JL: Biphasic carbon dioxide elimination waveform with right mainstem bronchial intubation. Anesth Analg 1989;69:829-32.
1. Mokriski BLK, Nagle SE, Fragneto RY: Does the expired carbon dioxide waveform suggest endobronchial intubation? [Letter]. J Clin Anesth 1990;2: 140-1. 2. Martin L, Zupan J, Benumof JL: Unusual end-tidal CO, waveform. Anesthesiology 1987;66:712-3. 3. Zupan J, Martin L, BenumofJL: End-tidal CO, excretion waveform and error with gas sampling line leak. Ane.rth Analg 1988;67:579-81. 4. Gilbert D, Benumof JL: Biphasic carbon dioxide elimination waveform with right mainstem bronchial intubation. Anesth Analg 1989;69:829-32.
80
J. Clin. Anesth.,
vol. 3, JanuaryiFebruary
1991
