Unidirectional valve malfunction by the breakage or malposition of disc - two cases report -
A 23-year old man was admitted for tonsillectomy to our hospital. The preoperative laboratory findings were all within normal limits. The patient was premedicated with intramuscular injection of glycopyrrolate 0.2 mg and midazolam 2 mg 30 minutes before induction of anesthesia. When the patient arrived at the operating room, blood pressure was 110/70 mmHg, heart rate 61 beats/min, respiratory rate 14 times/min, and SpO2 98%. After a normal preanesthetic leak test by closing the pop-off valve, occluding the Y-piece, and pressurizing the circuit to 30 cmH2O with the oxygen flush valve and flow test by using the ventilator and a breathing bag attached to the "Y"-piece as described in the 1993 FDA Anesthesia Apparatus Checkout Recommendations [] on the breathing circuit, propofol 140 mg and rocuronium 30 mg were given intravenously, followed by an uneventful endotracheal intubation. The SpO2 was 100% and ETCO2 measured through a sidestream capnometer (S/5™ Compact Anesthesia Monitor, Datax-Ohmeda, Finland) was 38 mmHg after intubation. Following confirmation that there were no problems with ventilation in both lungs, a tube was fixed in the area that was 23 cm away from the incisor. The anesthesia ventilator (Aestiva/5, Datex-Ohmeda, Madison, USA) was set at volume control mode (tidal volume 600 ml, respiratory rate 12 times/min, I/E ratio 1 : 2). At that time, ETCO2 increased to 46 mmHg, PICO2 of 4 mmHg, and a gradually sloping descending limb of inspiratory phase were noted, which implied inspiratory valve malfunction (). Blood pressure was 156/87 mmHg and heart rate was 75 beats/min. When we inspected the inspiratory valve through the transparent dome, the disc was not located in the center, horizontally. We disassembled the unidirectional valve component right away, which revealed an improper orientation of disc and disc locking apparatus (). After correction, the capnogram waveform returned to normal. The surgery was completed smoothly and the patient had an uneventful recovery.