Expired oxygen as the unappreciated issue in preventing airway fires: Getting to 'never'

摘要

Conventional wisdom and traditional habits need to be challenged continually to help understand and, thus, advance clinical practice. Many features of routine anesthesia protocols have evolved over time because they seem logical and are faithfully drilled into trainees by well-meaning faculty members who learned them from their teachers, and so on.... In this issue of the journal, Remz and colleagues1 address the conventional teaching that reducing the inspired oxygen concentration will prevent an airway fire when an ignition source is used in the airway. All trainees see images of the dramatic "blowtorch ignition" of a plastic endotracheal tube through which 100% oxygen is flowing2 (simulating a recognized danger during a "simple, routine" tracheostomy)3-5 (Fig. 1). Airway fires are usually reported by otolaryngologists or anesthesiologists and have involved all types of surgery in the airway6 including the common tonsillectomy7 Ever since identification of the danger of a fire in a patient's airway, ignited by an elec-trocautery, a laser, or a fiberoptic light, the "wisdom" handed down has been that the inspired oxygen concentration delivered from the anesthesia machine should be made <30% (Fio2 <0.30) or reduced to the "minimum possible" to limit the dramatic increase in flammability of plastic, cloth, and tissue in an oxygen-enriched environment. Remz and colleagues1 posit that the real issue is not only the inspired oxygen concentration but also the expired concentration.. .Using a simulation model, they demonstrated that the relation between the 2 depends on several factors and, importantly, that expired oxygen concentration may be increased for a considerable period of time after the inspired concentration appears to be "safe," which could create an unexpected, occult risk of airway fire. These findings necessitate a reevaluation of our wisdom and expansion of conventional teaching to recognize the role of expired oxygen in mitigating the risk of airway fires.