Flow transducer gas leak detected after induction.

Abstract

We report a leak in the Flow Transducer 22F/22M used on the Ohmeda Anesthesia Modulus SE with 7900 series Smart Ventilator (Ohmeda, Madison, WI) which was not noticed during routine preinduction machine check. This leak became evident only after commencement of controlled ventilation of our patient. Before the induction of anesthesia, the machine was routinely checked. A low-pressure test did not indicate any gas leak. Rapid-sequence IV induction was uneventful. After endotracheal tube placement and confirmation, the ventilator was turned on, but the machine was unable to provide the set tidal volume. A second check for a possible leak was done. This included adding air to the endotracheal tube cuff suction, checking all circuit connections, the soda lime canister seals, and the scavenging suction system. Manual ventilation with the bag did not sustain adequate pressure. Emergency ventilation was then provided with a Baxter resuscitation bag using oxygen from a wall outlet. Later inspection of the anesthesia machine revealed a fault in the small tubing (2.1-mm lumen) of the flow transducer that was used on the expiratory limb (Figure 1). Because the defect was not detected during the anesthesia machine check for gas leaks, it is possible that moving the anesthesia machine or patient cables caused traction on the circuit that opened a nick in the flow transducer tubing, which caused the gas leak. Further inspection of this flow transducer showed that, when traction on the tubing was removed, an adequate seal allowing high-pressure and rate ventilation was restored. We were able to find the small, torn flow transducer by running our alcohol-wet hands over the circuit tubing. This technique of using alcohol-wet hands to perform tactile inspection of the circuit tubing allows for easier detection of small gas leaks because the leaking gas evaporates the alcohol and cools the skin, alerting the physician. Figure 1: Cut in small tubing connecting the flow transducer to the monitor.We recommend that this vulnerable spot be checked should an unexplained anesthesia machine gas leak occur. Padmani Dhar MD Ivan George AA Aparna Mankad MD Paul Sloan MD