Effect of tracheostomy tube on work of breathing: Comparison of pre- and post-decannulation
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.