One of the functions of an endotracheal tube (ETT) is to prevent aspiration of fluid or particulate matter into the airway.
This is achieved by using ETTs with inflatable cuffs. However, these can cause tracheal damage, including rupture. Tracheal
rupture occurs most commonly in cats and is often associated with dental procedures.1, 2 One theory is that because of the fear of fluid aspiration during a dental prodecure, the cuffs are often overinflated. Applying
gel to an ETT before insertion helps it slide more easily into the trachea and prevents tissue damage, but it serves another
important function: The gel enhances the seal produced by the cuff, especially high-volume, low-pressure cuffs.
I read a study that compared lubricated ETT cuffs with nonlubricated cuffs for passage of dye past the cuff in both a bench-top
model and in anesthetized people3 and I wanted to see this effect for myself. I placed a high-volume, low-pressure ETT into a rigid glass tube—the first cuff
was dry and the second cuff was lubricated with gel. Each cuff was inflated with the same volume of air, which was minimal
in this setting. I then poured colored water into the glass tube above the ETT to simulate fluid in the trachea, and observed
whether fluid appeared below the cuff. The results are obvious: The gel helps prevent "aspiration" past the cuff.
The results of the study in people revealed that the incidence of dye leakage past the cuff in their bench top model was 0%
in the lubricated cuff group vs. 100% in the nonlubricated cuff group. In anesthetized people, leakage was 11% in the lubricated
group vs. 83% in the nonlubricated groups. The researchers concluded that lubricating the cuff with water-soluble gel reduces
pulmonary aspiration in anesthetized patients.
Gel is easier to apply evenly when the cuff is inflated—and the cuff should always be inflated before every use to check its
integrity. We recommend checking the cuff before use by fully inflating it, leaving it inflated, then applying the gel and
deflating the cuff immediately before the ETT is to be used. After intubation, check for a leak by listening to the patient's
airway as the reservoir bag is squeezed. Add air to the cuff in small increments until you no longer hear a leak when the
pressure gauge reads 15 cm H2O. The careful application of gel to the cuff decreases leakage past the cuff and may provide a seal with less air in the
cuff, which could potentially decrease tracheal trauma.
Sheilah Robertson BVMS (Hons), PhD, DACVA, DECVAA, MRCVS
Gainesville, Fla.
REFERENCES
1. Hardie EM, Spodnick GJ, Gilson SD, et al. Tracheal rupture in cats: 16 cases (1983-1998). J Am Vet Med Assoc 1999;214(4): 5085-12.
2. Mitchell SL, McCarthy R, Rudloff E, et al. Tracheal rupture associated with intubation in cats: 20 cases (1996-1998). J Am Vet Med Assoc 2000;216(10): 1592-1595.
3. Blunt MC, Young PJ, Patil A, et al. Gel lubrication of the tracheal tube cuff reduces pulmonary aspiration. Anesthesiology 2001;95(2): 377-381.
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