A Nasal Catheter for the Measurement of End-Tidal Carbon Dioxide in Spontaneously Breathing Patients: A Preliminary Evaluation

Several devices have been proposed to monitor end-tidal carbon dioxide tension (Petco(2)) in spontaneously breathing patients; however, many have been reported to be inaccurate. We designed this study to investigate the accuracy of a balloon-tipped nasal catheter in measuring Petco(2) in nontracheally intubated, spontaneously breathing patients. The catheter was assembled using a 14-F rubber Foley catheter, a tracheal tube pilot balloon, and the plastic sheath from an 18-gauge needle. The catheter was connected to the sampling tube of a gas analyzer. Petco(2) and Paco(2) were determined simultaneously in 20 otherwise healthy postsurgical patients while receiving oxygen. The mean Petco(2) - Paco(2) difference was -4.4 +/- 1.6 (SD) mm Hg with a correlation coefficient r = +0.87 (P < 0.001). Our results suggest that a balloon-tipped nasal catheter can provide a simple, easy, and reliable method for Petco(2) measurement in nontracheally intubated, spontaneously breathing patients.