Capnographic waveforms in esophageal intubation: effect of carbonated beverages

Capnography is a useful tool in differentiating tracheal from esophageal intubation. It may be an especially useful tool in emergency airway management by rescue squads or in the emergency department. However, in clinical practice the question has arisen as to whether prior ingestion of carbonated beverages can generate false-positive capnographic evidence of endotracheal intubation when in fact esophageal intubation has occurred. To answer this question, we compared the difference between tracheal and esophageal capnographic waveforms in dogs in the setting of recent ingestion of carbonated beverages. Esophageal capnographic recordings from three of five dogs undergoing esophageal ventilation were strikingly positive for exhaled carbon dioxide; however, the waveforms were significantly different from waveforms of tracheal ventilation. We conclude that esophageal intubation, after recent ingestion of carbonated beverages, may give false-positive waveforms suggestive of tracheal intubation. Rapidly diminishing CO2 concentrations, however, help differentiate esophageal from tracheal ventilation in this setting.