To the Editor:

—Continued pressure to minimize anesthesia costs inspired us to suggest a simple technique for monitoring exhaled carbon dioxide in patients spontaneously breathing oxygen through a clear plastic face mask. In the past, we have inserted an intravenous catheter with the needle removed through a hole in the side of the mask, so that the female hub of the intravenous catheter wedged into the side hole of the mask. However, the cost for each catheter was approximately $1.75 (14G 1-1/4″ Protectiv-Plus; Johnson & Johnson Medical, Arlington, TX). The same results can be obtained by using the cap from a syringe (Slip Tip Syringe; Becton Dickinson & Co., Franklin Lakes, NJ). The cap is removed from one of the many syringes used for a given patient. The closed tip of the cap is removed at an angle using scissors, and the cap is inserted into one of the face mask holes (See-Thru Oxygen Mask; Hudson Respiratory Care Inc., Temecula, CA). Because the cap is designed to mate with the male end of a syringe, it provides an ideal secure link to the male end of the capnograph sampling line.