Flow sensor fault during induction

Abstract

The flow sensor, while a robust and reliable component of an anesthesia machine, can be a somewhat underappreciated source of significant problems. On one occasion, after intubation for general anesthesia, we set the inspiratory pressure to switch to the ventilator and started mechanical ventilation in the pressure control mode. Nevertheless, the screen of the anesthesia machine (Dräger Fabius Plus; Drägerwerk AG & Co. KGaA, Lübeck, Germany) did not display any information on tidal volume, minute ventilation, positive end-expiratory pressure, or plateau pressure; instead, a comment on the screen appeared that said, ‘‘Check the flow sensor!’’ (Figure, panel A). Since the scheduled surgical time was short, we elected to perform manual ventilation for anesthesia management. After the procedure, the anesthesia machine was examined by a medical engineer. It was revealed that a disconnection of the hot-wire anemometer in the flow sensor was the source of the problem (Figure, panel B). We had followed the manual instructions for the anesthesia machine and performed a start-up inspection every time the machine was used before the patient entered the operating room. Display of tidal volumes had been confirmed on the screen during bag-mask ventilation. The fault occurred when we switched from manual to mechanical ventilation. We did not replace flow sensors regularly, and this particular flow sensor had been last changed six years before the event. According to the manufacturer’s recommendations, these flow sensors can be used as long as their calibration is successful. From the perspective of medical safety, it may be useful to regularly replace flow sensors as a preventative measure. We used the carbon dioxide (CO2) absorbent Drägersorb 800? (Dräger Japan, Tokyo, Japan), which is said to generate less dust than other products because it has an internal dust filter. The dust produced by CO2 absorbents may also contribute to the deterioration of flow sensors. Despite adequate inspection and preparation, certain problems are inevitable. The chief priority in such a situation is to identify the cause of the problem and manage it while maintaining the safety of the patient. We would suggest that standardized protocols be prepared that address such an emergency to facilitate a quick response intraoperatively. Additionally, more user-friendly interfaces of anesthesia machines may allow easier identification of the faulty part, and based on our