Background: A fatal incident was reported when a mechanical ventilated patient received nebulization of a reconstituted Relenza® formulation. We propose a delivery system to introduce Relenza and other inhalation dry powders to intubated patients to avoid accidental fatalities in the future.
Methods: This is a bench study demonstrating the feasibility of a delivery system to introduce dry powder of Relenza to intubated patients. A dry powder inhaler placed within a delivery chamber was actuated by compressing a ventilation bag to disperse powder into a tracheal tube. The performance of two inhalers, a Diskhaler® and an Osmohaler™, were compared. The effects of the length and size of the tracheal tube on the powder output and sizing of emitted powder were investigated using the more efficient Osmohaler™.
Results: The efficiency of Osmohaler in delivering Relenza to the distal end [delivered dose=30.2±0.2% and fine particle fraction (FPF)=14.5±1.7%] was significantly higher than the Diskhaler (delivered dose=18.1±4.7% and FPF=3.4±2.1%). While no differences in the delivered dose and FPF were observed between the tracheostomy and endotracheal tubes of the same internal diameter, a larger endotracheal tube (9.0 mm internal diameter) gave a 6% higher FPF compared with the smaller counterpart (7.0 mm internal diameter).
Conclusion: The dry powder delivery system has been demonstrated to be capable of delivering Relenza formulation to the distal end of tracheal tubes with a reasonable delivered dose and FPF. It would be necessary for further investigation into incorporating the proposed powder delivery system within a mechanical ventilator, as well as animal and clinical studies to prove its applicability to deliver zanamivir dry powder to ventilated influenza patients in the intensive care setting.
Keywords: dry powder inhaler; endotracheal tube; influenza virus A (H1N1); tracheostomy tube; ventilated patients.