I was called to the ICU to replace an endotracheal tube because air was leaking around the cuff and the respiratory therapist could not maintain a good tracheal seal, even after re-inflating the pilot balloon. Knowing the differential diagnosis of an endotracheal tube that no longer maintains a seal can avoid unnecessary tube exchanges. Even more important is taking precautions to avoid having to change the tube to begin with.

Differential Diagnosis of Persistent Cuff Leak

When an endotracheal tube cuff can’t maintain a tracheal seal, the most common causes are a damaged endotracheal tube cuff or a cuff positioned above the cords. More rarely the pilot balloon injection port assembly may fail.

If the endotracheal tube cuff is ruptured, no matter how much air you inject into the pilot balloon, the balloon keeps deflating and becomes soft.

If the cuff is intact, but the cuff is above the cords, then no matter how much air is injected into the pilot balloon, the leak persists and may worsen. The pilot balloon gets more and more tense and distended. In this case the cuff is now acting like a cork sitting on top of the vocal cords, with just the very tip of the tube in the trachea. The more air in the cuff, the bigger and rounder the cuff becomes and the less seal one has as the tube rises out of the trachea. There is a high risk of accidental extubation in this situation.

If the pilot balloon injection port assembly fails, inserting a closed stopcock into the assembly plugs the leak and allows the pilot balloon to remain inflated. While tube replacement is recommended with a faulty pilot tube assembly, this trick may save you from having to urgently exchange a damaged endotracheal tube in an unstable patient.

Case Discussion

When I checked the cuff in the ICU patient, the pilot balloon kept slowly deflating.  Blocking the pilot assembly didn’t help. Therefore, we felt certain that we had a cuff leak and needed to exchange the tube.

Exchanging an endotracheal tube in an ICU patient is never an easy process because the patient is dependent on ventilator support and is often hemodynamically fragile. The airway may be compromised by edema or trauma- surgical or otherwise. The patient’s position in the bed may make intubation awkward. So even a patient who was easy to intubate initially may be difficult to reintubate after extubation. Careful and judicious sedation, possible muscle relaxation, and gentle technique must be used.  We often use a combination of intubation tools and an endotracheal tube exchanger. Have everything you might need available before you start, including working suction, because getting it later once the intubation has begun may not be a safe option.

In this case I used a tube exchanger, but I had a laryngoscope and Glidescope standing by in case I had difficulty. The process went smoothly and the patient did well. When I checked the old tube to see what had caused the problem, I was surprised to see that the cuff appeared intact, as did the pilot balloon itself. I injected some saline into the pilot balloon to test it and discovered a pin hole in the pilot tube. We suddenly realized that the pilot tube had become trapped between the patient’s upper teeth and the protective sleeve that had been placed around the endotracheal tube to act as a bite block. The patient had bitten a pin hole in the pilot tube.

Bite blocks are important safety devices in ICU patients. In addition to blockage from kinking, blood clots or secretions or dislodgment, endotracheal tubes can easily obstruct due to patient biting. These complications can be life threatening or even fatal.

However, it’s important to use bite blocks carefully. Bite blocks can themselves cause tooth and tissue trauma.  The typical oral airway used during anesthesia is poorly tolerated by awake or semi-conscious patients. Oral airways are bulky, uncomfortable and stimulate the gag reflex. Instead, an around-the-tube sleeve is often used in the ICU setting.

The around-the tube style bite block used in this patient was designed to allow the pilot tube to run inside the bite block sleeve, between the endotracheal tube and the sleeve. This position protects the pilot tubing. In our patient, the pilot tubing had slipped outside the sleeve to lie between the upper teeth and the bite block. This allowed the patient’s teeth to puncture the tubing and led to the need to exchange the tube.

A video showing how to place one common type of oral bite block sleeve can be found at the Bandb-Medical website. Other brands are available but all rely on the sleeve to protect both the tube and the pilot tubing.

I had never seen this particular complication before, but it does show that if anything can go wrong, it will go wrong. Close attention to little details, no matter how small they may seem, can be important to your patient’s safety.

May The Force Be With You