To the Editor:—
End-tidal carbon dioxide (ETCO2) monitoring during spontaneous respiration is desirable. 1I had been previously using intravenous cannulae to attach carbon dioxide monitoring tubing to Hudson-style masks during cases involving intravenous sedation. The cannula cost $.53 and required scissors to cut off the excessive lengths, which protruded into the masks and “tickled” noses. Recently, the Intertech Gas sampling lines (order No. 225–3421–800; Smith Industries Medical Systems, Fort Meyers, FL) have become standard in our operating rooms (fig. 1
). These lines have Luer-lock hubs with an internal 4-mm long and 4-mm diameter “male” protrusion. The hub can be twisted into and quickly secured within a vent hole of standard Hudson-style (Hudson Respiratory Care, Temecula, CA) oxygen masks when counterpressure is applied from inside the mask. In this way, the additional costs are eliminated to secure carbon dioxide monitoring devices onto standard masks as is the need to carry scissors to trim intravenous catheters. I recommend this method, which allows inexpensive and hygienic ETCO2sampling, directly at the site of expired gas egress. Because the Hudson mask collects expired gases from both the mouth and the nose, this type of monitoring device is very effective in detecting carbon dioxide, irrespective of whether “mouth” or “nose” breathers are encountered. I also recommend looping the carbon dioxide sampling line under the Hudson mask strap to prevent inadvertent dislodgement of the line from the Hudson mask via incidental traction on the sampling line. This facilitates secure intraoperative placement and rapid removal at the end of the case.