Physiological effects of decannulation in tracheostomized patients

Objective: To evaluate the physiological effects of decannulation on breathing patterns and respiratory mechanics by comparing mouth breathing (MB) to tracheal breathing (TB) in tracheostomized patients. Design and setting: Prospective cross-over study in a critical and neuromuscular care unit. Patients and methods: Nine consecutive neuromuscular tracheostomized patients. Flow, esophageal pressure, gastric pressure, expiratory gas, And arterial blood gases were measured during MB and TB. Results: MB induced an increase in tidal volume (from 330 +/- 60 ml to 400 +/- 80 ml) without changing respiratory frequency, inspiratory time, or arterial CO2 pressure. This ventilation increase was due to a significant increase in physiological dead space (from 156 +/- 67 to 230 +/- 82 ml) and was associated with significant increases in work of breathing (from 6.9 +/- 3.4 to 9.1 +/- 3.3 J/min), transdiaphragmatic pressure swing (from 10 +/- 4 to 12.5 +/- 7 cmH(2)O), diaphragmatic pressure-time product per minute (from 214 +/- 100 to 271 +/- 92 cmH(2)O s(-1) min(-1)), and oxygen uptake (from 206 +/- 30 to 229 +/- 34 ml/min). Upper airway resistance did not differ from in vitro tracheostomy tube resistance. In addition, total lung-airway resistance, dynamic pulmonary compliance, and intrinsic positive end-expiratory pressure were similar in both conditions. Conclusions: Decannulation resulted in a dead space increase with no other detectable additional loading. It increased work of breathing by more than 30%. Decannulation deserves special attention in patients with restrictive respiratory disease.