The effect of inner tube placement on resistance and work of breathing through tracheostomy tubes: a bench test.

To reduce the risk of tracheostomy tube blockage, a removable inner tube can be used. However, this will reduce the size of the lumen and will increase airflow resistance and work of breathing. The magnitude of this increase in workload is unknown. We undertook a bench test to measure the effect. A lung model was developed to 'breathe' through the tracheostomy tube. We created pressure-volume curves from which we calculated work of breathing with and without an inner tube using 6-10 mm tracheostomy tubes over a range of respiratory rates and tidal volumes. The inner tube increased the resistive work of breathing by an average factor of 2.2. The extra work of breathing imposed easily exceeded the normal total work of breathing. Our results will aid a risk-benefit analysis when deciding whether to use inner tubes. Selecting a larger tracheostomy tube is likely to aid weaning from mechanical ventilation. Anaesthesia