A review1 of tracheal rupture in 20 cats is very helpful to better understand and prevent this unfortunate iatrogenic complication.
Intubation of a patient and insufflation of the cuff of the endotracheal tube are not risk-free procedures. Clinical signs can occur within a few hours to a few days. Classic signs include subcutaneous emphysema (100 percent), dyspnea (30 percent) and respiratory stridor (15 percent).
Thoracic radiographs always reveal subcutaneous emphysema in the neck, and sometimes a pneumothorax or a pneumomediastinum.
Early signs are due to physical damage to the trachea because of overzealous inflation of the endotracheal tube cuff. Delayed signs are related to progressive ischemic injury of the trachea, also because of overinflation of the cuff.
In another study2, 1.6 ml was enough to ensure an airtight seal, with a maximum of 2.3 ml. Injecting 6 ml caused a tracheal tear in most cases.
Most tears occur at the thoracic inlet, at the level of the cuff. The classic location is dorsolaterally, at the junction of the cartilagenous rings and the tracheal muscle.
Fifteen patients with moderate dyspnea are treated medically, with cage rest and oxygen therapy. The subcutaneous emphysema is reabsorbed in one to six weeks.
Four patients with severe dyspnea required surgery. Either they did not respond to conservative management or their SQ emphysema became progressively worse. The 20th cat died before surgery.
Based on interviews with liability insurers, the author suggests five techniques to avoid tracheal tears in cats:
• Do not overinflate the cuff.
• Do not “flip” the patient without first disconnecting the endotracheal tube.
• Do not overinflate the cuff, even for a dental.
• If a metal stylet must be used to stiffen an endotracheal tube, it should not stick out beyond the end of the tube.
• Never extubate a patient without first deflating the cuff.
Interestingly, 70 percent of the cats in this study had a ruptured trachea during a dental procedure, presumably because the cuff was overinflated to prevent fluid and debris aspiration.