Increasing the margin of safety during fiberoptic-guided intubation: Use of a jet ventilator.

Sir,

Although awake tracheal intubation is a universally accepted technique for preoperative airway management of adult patients with a known difficult airway, in children, most anesthesiologists induce anesthesia with inhalational agents before attempting the same. With widespread availability and use of flexible fiberoptic bronchoscopes (FFB), the device has become the gold standard in the management of difficult airway. They are, however, fraught with their own difficulties. Firstly, the clarity of vision diminishes drastically if even a single drop of secretion, or worse, blood, touches the tip of the scope. Secondly, although more advantageous than other devices, the FFB also encounters problems in accomplishing tracheal intubation in patients with altered airway anatomy. This results in prolongation of intubation time, which might be unacceptable in patients with compromised airway patency, especially after general anesthesia. Working in a maxillofacial anesthesia unit of a tertiary-level hospital, we were facing these problems day-in and day-out before we made a slight alteration in our intubation strategy. For all patients with difficult airway who require general anesthesia before FFB-guided intubation, we attach a three-way stopcock to the suction port of the FFB. To one of the ports of the three-way stopcock, we attach the high-pressure tubing of a jet ventilator. The other port is connected to a vacuum source. The drug port is kept dedicated to the instillation of medications if necessary [Figure 1]. After taking a written, informed consent, anesthesia is induced with Sevoflurane 5–8% in oxygen, administered via an anesthesia facemask. Once proper depth of anesthesia has been achieved, the FFB is negotiated toward the larynx through the more patent nostril. An assistant operates the jet ventilator at a driving pressure of 55 pounds/inch2 and a frequency of 8–12/min in short bursts of 1 s each. If required, another assistant applies cricoid pressure to prevent gastric insufflation. This serves three purposes – firstly, the tip of the FFB remains clean as the jet of gases prevents secretions and blood from fogging the tip; secondly, the collapse of pharyngeal structures is prevented by the regular flow of gases, which results in a better bronchoscopic view and manoeuvrability; and thirdly; the hemoglobin saturation is maintained, which permits the operator to work without the pressure of a time limit. If there is a need to suction secretions, the stopcock can be momentarily rotated to connect the vacuum source. Depth of anesthesia, in the meantime, can be maintained with an infusion of propofol. Critics may argue that the same can be achieved by oxygen insufflation through a naso-pharyngeal airway or the suction port of the FFB, especially with the patient breathing spontaneously, but we feel that the first two benefits cannot be achieved fully with the latter technique. Arguments can also be made that the jet ventilator could, instead, have been connected to the drug port by the same mechanism, with the suction port dedicated to vacuum only. We decided against that, as simultaneous use of the jet ventilator and the suction machine would have rendered both procedures ineffective.

Figure 1

The assembly showing the jet ventilator and vacuum attached by a three-way stopcock to the suction port of the fiberoptic bronchoscopes

The use of this technique along with jet ventilation can also be extrapolated to unanticipated difficult airway situations, where neuro-muscular blocking agents have been given to the patient before the gravity of the situation is realized. Similar use has been described previously in a number of studies, but all of them compromised on the use of suction during the procedure.[1-3] We present our technique to the learned readers and encourage them to use it and share their experiences.