To the Editor:--We would like to bring to attention an unusual cause of a leak in the breathing circuit of a circle anesthesia system involving the carbon dioxide absorber canister (Soda-Sorb NSN 6505-00-782-6484, WR Grace, Lexington, MA).
During a routine preuse machine check, we noted a leak within the breathing system. Visual inspection of the breathing circuit did not reveal the source of the leak, and all joints appeared to be intact. A draft could be felt near the carbon dioxide canisters, initially, we thought that they were misaligned and removed them and changed them from top to bottom. However, the leak persisted. Thinking that the absorbers were still out of alignment, we removed them from the housing. This caused some free granules to fall to the floor. On closer inspection of the canister, it was noted to be defective. The canister is made of a clear plastic cylinder, filled with absorbent granules and covered with a perforated lid, which is then heat-sealed to the top edge of the cylinder. This canister was defective because the edge of the lid had not been properly seated with the canister before heat-sealing. The height of a correctly sealed canister is 89 mm; our canister edge was 94 mm, leaving a 5-mm increase in canister height (Figure 1). This resulted in a gap between the lid and the side wall of the canister, which allowed gases to escape from the breathing circiut. The problem was easily solved by replacing the canister. However, this case reiterates the need to conduct a thorough preuse check of the anesthesia machine.
A. M. Kshatri, M.D., Resident of Anesthesia.
C. P. Kingsley, M.D., Associate Professor Anesthesia, Department of Anesthesia, Pennsylvania State University, P.O. Box 850, Hershey, Pennsylvania 17033.