[Hypoventilation due to disconnection of the vaporizer and negative-pressure leak test to find disconnection].

Most of Ohmeda anesthesia machines have a outlet check valve located in the low-pressure circuit, and this influences the type of leak test greatly. We report a case of hypoventilation due to a gas leakage from the junction of two vaporizers, Fluotec 3 and Enfluratec of Ohio 30/70. This gas leakage was not discovered preoperatively by performing traditional leak test of squeezing the bag filled with oxygen. Following intubation of the trachea the patient was paralyzed and mechanically ventilated. Her vital signs were stable and operation was started. Soon thereafter, she became hypertensive in spite of increases in concentration of enflurane and supplemental doses of fentanyl and diltiazem. ETCO2 showed 7.4% and spontaneous respiration started. We checked anesthesia machine and found a gas leakage at the junction of two vaporizers. Anesthesia machine was exchanged. The remainder of the procedure was uneventful and the patient showed a normal recovery. The outlet check valve closes when back-pressure is exerted on it, and a vulnerable area including flow tubes and vaporizers is not tested by the traditional positive-pressure leak test squeezing bag. Ohmeda recommends the use of a negative pressure leak test with suction bulb device. We propose manufacturers to place a cation on anesthesia machine such as -- "Negative-pressure leak test is inevitable because of presence of outlet check valve."