Physiological effects of decannulation in tracheostomized patients

Abstract

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 cmH2O), diaphragmatic pressure-time product per minute (from 214±100 to 271±92 cmH2O 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.