Real-Time Analysis of the Respiratory Flow Through a Valved Holding Chamber

The ability of patients to take, correctly and regularly, aerosol treatments is a key for good control of asthma and chronic obstructive pulmonary disease. Devices that help to improve inhalation technique could train the patient to take their medication properly, reducing risk of exacerbations. In this study we evaluate a new device that by recording real-time respiratory flow into the valved holding chamber (VHC) mouthpiece, could be used to improve patient technique. Using computational fluid dynamics analysis we demonstrated that compared to a mouthpiece with no flow probe, the presence of a probe modifies the flow profile and velocity regardless of the probe shape or position. During flow measurement using a SDP610 pressure sensor (Sensirion, Switzerland), all probes can accurately record adult and child respiratory patterns. Resistance was determined from the back pressure generated by the VHC with or without probes; and resistance was not impacted by the probes. Aerodynamic particle size distribution and drug delivery measurement were assessed using the United States Pharmacopeia throat model (Copley Scientific, UK), next generation impactor (NGI; Copley Scientific), and a breath simulator (BRS200; Copley Scientific). To test different formulations, these experiments were performed with fluticasone propionate (Flixotide^®; GSK, UK), salbutamol (Ventolin^®; GSK), and beclomethasone dipropionate (BDP) (QvarSpray^®; GSK). Depending on the molecule or the probe configuration, we noticed a decrease of the emitted doses, fine particle deposition, mass median aerodynamic diameter, but no significant change in the mass of drug delivered. A decrease in the fine particle fraction (FPF) was observed in most testing conditions. However, a slight increase was noticed for two conformations with BDP (round and close [Rc] and diamond and far [Df]) and salbutamol (Rc and round and far [Rf]). By inserting a flow probe directly into the mouthpiece of a VHC we could perform real-time analysis of respiratory flow during the VHC use without disturbing drug delivery, or increasing resistance.