In-vitro evaluation of pressurized metered dose inhalers in high flow oxygen system

Abstract

Background: The growing application of high flow oxygen systems in hospital settings encourages attempts to improve aerosol delivery within these circuits to patients in need of inhalation therapy together with respiratory aid which can be achieved by changing the type of inhaler device, its position within the circuit, patient interface and the type of humidifier.

Aim and Objectives: The current work aims at quantifying the delivered dose by pressurized metered dose inhaler (pMDI) with spacer in high flow oxygen system at different flow rates using different patient interfaces to determine whether this dose is sufficient to produce a significant therapeutic response.

Methods: Aerochamber vent (VC) attached to pMDI was placed in high flow oxygen circuit in a proximal position to the humidifier where the experiment was carried at three set oxygen flow rates of 10, 20, 30 L/min using three interfaces: nasal cannula, mouthpiece and valved mask. For control, the same procedure was repeated for each interface with no oxygen delivery. The delivered dose and deposited fractions in any part of the circuit were measured using high performance liquid chromatography.

Results: For nasal cannula, 20.7, 3.1, 1% of nominal dose was delivered at 10, 20, 30 L/min, respectively with the significant drop in delivery with increasing flow rate (p<0.0001) while the highest delivered dose (30% of nominal dose) was reported with valved mask at 10 L/min oxygen flow rate.

Conclusions: pMDIs have proven high efficiency of aerosol delivery at low flow rates comparable to that of nebulizers within high flow systems which can recommend their use.