Capnography is an important monitor in anesthesia care that assists with detection of esophageal intubation and with assessment of ventilation. Preoperatively,1it is important to check the capnograph system on the anesthesia machine to detect any malfunctions before intubation, because there may be occlusion, incorrect attachment of the sampling tube,2or other problems. Unfortunately, the capnogram can still be lost intraoperatively as a result of mechanical failures of the sampling tube. We find that in cases with the bed turned 90° or 180° from the anesthesiologist, the sampling tube can kink at the connection with the breathing circuit Y-piece as a result of weight from draping or the surgical field. This results in loss of the capnogram because of occlusion, which causes both alarm and frustration because the anesthesia provider must investigate the source of the occlusion after appropriate patient ventilation is confirmed. Occasionally, brief interruption of the surgeon or scrub nurse is necessary. Traditionally, we have taped the sampling tube in a half-loop at this connection point; this prevents kinking somewhat with axial loads but still cannot prevent lateral motion and subsequent occlusion.

During a maxillofacial surgery case in which the capnometer sampling tube kinked multiple times, we discovered that the circuit elbow, normally set aside when flexible corrugated tubing is attached to the endotracheal tube, can be used to protect the sampling tube at the attachment with the Y-piece. Fortunately, the elbow piece is appropriately sized to allow passage of the tube while also creating a rigidly protected and controlled 90° bend (fig. 1). Tape is used to secure the elbow firmly against the Y-piece. This technique has become popular at our institution for helping prevent occlusion of the capnometer sampling tube and seems to provide better protection than taping the tube directly.

Fig. 1. Threading the sampling tube through the unused elbow. 

Fig. 1. Threading the sampling tube through the unused elbow. 

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*University of Michigan, Ann Arbor, Michigan.

Gauthama P, Morris E: Check the capnograph. Anaesthesia 2004; 59:304–5
Ho AM: Absent CO2 detection after tracheal intubation due to sampling line obstruction. J Clin Monit Comput 2000;16:229–