Aerosol delivery through tracheostomy tubes: an in vitro study

Our study investigated the influence of the cannula's inner diameter (ID) and of its removal on the expected respiratory dose of amikacin, using three different jet nebulizer configurations (Sidestream(®)): vented (N1), unvented with a piece of corrugated tubing attached to the expiratory limb of the T attachment (N2), and unvented alone (N3).

The jet nebulizer was filled with amikacin (500 mg/4 mL) and was attached to the tracheostomy tube. A lung model simulating spontaneous breathing was connected to the tracheostomy tube. A filter was connected between the nebulizer and the tracheostomy tube to measure the inhaled dose, and between the tracheostomy tube and the lung model to measure the respiratory dose. Different cannula IDs were tested (6.5, 8, 8.5, and 10 mm), and aerosol lost in the cannulas was determined.

Respiratory dose varied between 96±1 mg and 44±3 mg, with higher values observed with N2. The aerosol lost in the cannula was significant and represented up to 63% of the inhaled dose. There was a negative correlation between the cannula's ID and the aerosol lost in the cannula. After removal of the internal cannula, an increase in the respiratory dose of up to 31.3% was observed. We recommend removing the inner tracheostomy cannula to nebulize a larger amount of drug through a tracheostomy tube. Among the three jet nebulizer configurations studied, we recommend the unvented one with a piece of corrugated tubing attached to the expiratory limb of the T attachment.