Pathogenesis of tracheal stenosis following tracheostomy with a cuffed tube. An experimental study in dogs.

A study was undertaken to clarify the pathogenesis of tracheal stenosis complicating the use of cuffed tracheostomy tubes, a complication of increasing clinical significance. Tracheostomy with a cuffed inflated tube was established in dogs and was maintained for two weeks. The effects of tracheostomy were assessed by bronchoscopy, tracheography, and histology at the time of killing, eight weeks after extubation. Animals were divided into four groups, each mimicking a common clinical situation. A control group had uncuffed tubes. A method was designed to determine the pressure developed between the cuff and the tracheal wall. Cuff inflation was maintained at low pressure and at high pressure in a second and third group of animals. A fourth group of animals received prednisone during the two weeks of low pressure inflation. Tracheal stenosis, resembling the defect we have encountered in humans, occurred at the tracheostome in all animals. The greater the diameter of the tracheostomy tube relative to the tracheal diameter, the more severe was the resultant stenosis. Greater degrees of tracheal injury occurred with cuffed than with uncuffed tubes, and still greater injury was observed in animals in which high inflationary pressures or steroids were used. These findings suggest that tracheal stenosis complicating cuffed tracheostomy tubes is the result of ischaemic death of tracheal cartilage due to pressure and infection. Steroids used concomitantly accelerate these changes.