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Delivering Powder Aerosols During Invasive and Non-invasive Ventilation

Chan H, Okuda T, Tang P, Finlay WH, Phipps P, Rajbhandari D, Dhanani J, Leung S, Yu J, Brannan J.

Respiratory Drug Delivery 2018. Volume 1, 2018: 149-158.

Abstract:

Delivering powder aerosols during invasive and non-invasive ventilation opens up treatment options whereby drugs that are available in dry powder inhalers (DPIs) or required in high dose can be used. However, many hurdles exist with this special mode of aerosol powder delivery to patients via assisted ventilation. We have designed powder delivery systems coupled to nasal high flow (NHF) or a mechanical ventilator to study aerosolization performance of mannitol powders from a commercial DPI. With the NHF system, it took 4 seconds, 8 seconds, and 16 seconds to empty the powder from the capsule in the DPI at 60 L/min, 45 L/min, and 30 L/min, respectively. Powder deposition in the nasal airway replica (NAR) was increased with the dispersion flow rate and/or the inspiratory flow rate, showing 16-27%, 25-30% and 23-33% at nominal dispersion flows of 30, 45, and 60 L/min, respectively. About 10-20% of the loaded dose penetrated through the NAR and reached the Next Generation Impactor (NGI) which was connected down-stream of the NAR. However, overall the NHF system generated a fine particle fraction (FPF) below 5 μm of only 4-8% of the loaded dose.

For the invasive delivery mode, using a manual ventilation bag to supply compressed air to aerosolize powder in the DPI, 48-64% of the loaded dose was emitted from the distal end of tracheal tubes connected to the exit of the DPI, with the FPF<5 μm being 20-25% of the loaded dose. With this powder delivery system connected in-line to the ventilator, the percentage of dose delivered through the tracheal tube was 25-40% of the loaded dose, and the FPF<5 μm being 51-57% of the emitted aerosol, depending on the tracheal tube type and the flow rate. In both the NHF system and the mechanical ventilator, humidified air did not affect the powder delivery. These results have confirmed the feasibility of powder aerosol delivery to the lungs using assisted ventilator systems although further optimization is warranted.