To the Editor:—

We wish to describe an incident that recently occurred in our endoscopy suite. We consulted for a 55-yr-old obese woman (weight, 128 kg; height, 140 cm) with a history of obstructive sleep apnea that necessitated nasal continuous positive airway pressure at home. She was scheduled to undergo colonoscopy to evaluate rectal bleeding and cramping abdominal pain. Her baseline forced expiratory volume in 1 s was 0.67 l, and she was home oxygen dependent. Her room air oxygen saturation was 90–92%. When the anesthesia team was preparing the patient for the procedure, a respiratory therapist fit the patient with a continuous positive airway pressure mask.

In our endoscopy suite, there are two carbon dioxide (CO2) cylinders. CO2is used to insufflate the bowel, particularly in children who have had poor bowel preparation previous to the procedure. CO2is used to displace methane from the area where electrocautery is used, reducing the risk of fire or explosion. Recently, the flowmeter for these CO2cylinders had been mounted on the wall, in a conspicuous place. This flowmeter was identical in appearance to standard oxygen flowmeters seen at most institutions, complete with a green oxygen nipple. The only noticeable difference was the labeling of this flowmeter with “CARBON DIOXIDE” in small print. When the anesthesia team was preparing the patient for the colonoscopist, the respiratory therapist connected the oxygen supply line from the continuous positive airway pressure mask to this flowmeter on the wall.

Just before the initiation of gas flow, one member of our anesthesia team noticed the oxygen supply line to the continuous positive airway pressure machine attached to the CO2source. The line was immediately removed from the CO2outlet and connected to an oxygen gas outlet, which also was mounted on the wall. CO2was not administered to the patient. The colonoscopy was performed uneventfully, with the patient undergoing conscious sedation by the anesthesia team and with an uneventful postprocedure course.

As soon as the postprocedure course was completed, our Medical Engineering and the Respiratory Therapy departments came to the unit to discuss this critical incident. Clearly, there are many problems with this treatment situation, but, in an attempt to address the broader issues as well as remedy this immediate concern, a placard was put up to label the flowmeter clearly.

This case shows that other gases are in use in endoscopy suites and are sometimes poorly or inadequately labeled. Without special care and diligence on the part of the anesthesiologist, a crisis may have occurred. Similar circumstances have the potential to occur in magnetic resonance imaging suites, in hyperbaric chambers, and even in “standard” operating rooms designed for specific surgical procedures. We hope that this letter calls attention to the potential for such occurrences and stimulates dialogue to reduce such risks in the future.