Errors in tracheal pressure recording in patients with a tracheostomy tube--a model study

The recording of intratracheal pressure in patients breathing through a tracheostomy tube is marred by methodological problems. In model experiments it has been shown that the introduction of a recording catheter into the tracheostomy tube alters the recorded pressure by as much as 20-40%. To avoid such inaccuracy, a specially designed tracheostomy tube is proposed with an externally placed channel for introduction of the recording catheter. In in vivo measurements, recordings can be made at a distance of up to about 20 mm below the end of tube. Pressure recordings from this part of a model trachea are compared with results obtained from a reference pressure port 100 mm below the tube ending. The results show that it is possible to record expiratory pressure with good accuracy but that inspiratory pressure is still overestimated by 9-16%.