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Can Capnography Substitute for Auscultation in Sedation Cases?

Fisher, Quentin A. MD, FAAP

doi: 10.1213/01.ANE.0000151470.50760.4A
Letters to the Editor: Letters & Announcements

Professor of Anesthesia and Pediatrics; Director, Pediatric Anesthesia; Medstar-Georgetown University Hospital; Washington, DC; fish5q@radix.net

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To the Editor:

Soto et al. (1) found that the frequent apneas that occurred during IV sedation were readily detected by capnography but “none were detected by the anesthesia providers.” This is not surprising, since the anesthesia providers were not using continuous auscultation, and thus were constrained to recognize apnea visually. Had they used a simple precordial stethoscope placed in the suprasternal notch, I suspect that not only would all cases have been detected, but also before the 20-second lapse required for a CO2-based apnea alarm. Conceivably, an obstructive apnea lasting more than 20 seconds could evolve to negative pressure pulmonary edema.

Auscultation is effective in detecting partial airway obstruction, which often precedes complete obstruction, and hypoventilation preceding central apnea. Diminished and absent breath sounds are important findings! Of course, auscultation is not subject to lapses while the machine recalibrates.

Although modern electronic monitors have brought basic physiology into clinical management, they still do not substitute for the basic vigilance principle to “always stay in contact with the patient.” Possibilities include visual inspection, auscultation, hand on a breathing bag, or voice contact during light sedation. The authors dismissed auscultation by noting that its use has been declining in recent years. Their conclusion urging research into methods to diagnose antecedents of adverse outcomes might include teaching effective “hands-on” vigilance skills. Continuous auscultation with a well-fitted earpiece is unencumbering and best of all, provides abundant, free information about the patient not as easily obtained otherwise.

Quentin A. Fisher, MD, FAAP

Professor of Anesthesia and Pediatrics; Director, Pediatric Anesthesia; Medstar-Georgetown University Hospital; Washington, DC; fish5q@radix.net

Dr. Soto does not wish to respond.

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Reference

1. Soto RG, Fu ES, Vila H Jr, Miguel RV. Capnography accurately detects apnea during monitored anesthesia care. Anesth Analg 2004;99:379–82
© 2005 International Anesthesia Research Society