An unusual site for disconnection in a ventilated patient.

Sir,

Rashmi Jain and colleagues[1] reported the loss of integrity of a reinforced endotracheal tube by patient bite and advocated the use of bite block to prevent it. Similar cases have been reported previously also.[23] We would like to present a case where a reinforced endotracheal tube was bitten despite a bite block leading to disconnection alarm from ventilator.

A 24-year-old female was diagnosed with fracture dorsal spine (D6) and 3rd-7th rib fracture (right side). The patient was scheduled for laminectomy and posterior fixation in the prone position. After administration of general anaesthesia, her trachea was intubated with 7.5-mm, cuffed, reinforced endotracheal tube (Portex®, Smiths Medical International Ltd). A soft gauze bite block was placed between incisors. Surgery lasted for 12 hours. In view of prolonged duration of surgery, it was decided to ventilate the patient overnight. Postoperatively, the patient was shifted to neurosurgical intensive care unit with the endotracheal tube and the soft gauze bite block in situ. Two hours later, anaesthesiologist was called to evaluate disconnection alarm from the mechanical ventilator. However, even after proper examination, the site could not be ascertained. The patient had adequate and regular respiratory efforts. Arterial blood gas analysis was done which was within normal limits. It was then decided to extubate her trachea. After extubation, a close examination of the endotracheal tube revealed a tear, which was likely corresponding to the patient's molars [Figure 1].

Figure 1

Torn tube due to bite at the level of molars

Biting has been a major concern for intubated patients who are not paralysed, especially with a wire-reinforced, flexometallic endotracheal tube. Oropharyngeal airway (OPA) has been advocated for the prevention of biting. However, a patient in a semi-conscious state can push out the airway and the ETT between the molars and bite on it. Thus, oral airways may not completely prevent the biting of the tube.[45] It is also poorly tolerated by conscious patient.

Negus[4] used and recommended a soft gauze bite block as a cheap, safe and effective alternative to OPA. He rolled a pack of four or five gauzes into a very tight cylinder and inserted it between the upper and lower molars. As there is no contact with the posterior pharyngeal wall, it is less likely to evoke airway reflexes. However in our patient, the tube was torn despite a similar bite block. It might be because of improper placement.

We would further like to stress the fact that the reinforced endotracheal tube should ideally be replaced with a normal endotracheal tube. It might be difficult to change the tube, especially in cases like cervical spine injury for which an airway exchanger or even a fiberscope may be required.