Lung Deposition and Inspiratory Flow Rate in Patients with Chronic Obstructive Pulmonary Disease Using Different Inhalation Devices: A Systematic Literature Review and Expert Opinion

BACKGROUND: Our aim was to describe: 1) lung deposition and inspiratory flow rate; 2) main characteristics of inhaler devices in chronic obstructive pulmonary disease (COPD). METHODS: A systematic literature review (SLR) was conducted to analyze the features and results of inhaler devices in COPD patients. These devices included pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs), and a soft mist inhaler (SMI). Inclusion and exclusion criteria were established, as well as search strategies (Medline, Embase, and the Cochrane Library up to April 2019). In vitro and in vivo studies were included. Two reviewers selected articles, collected and analyzed data independently. Narrative searches complemented the SLR. We discussed the results of the reviews in a nominal group meeting and agreed on various general principles and recommendations. RESULTS: The SLR included 71 articles, some were of low–moderate quality, and there was great variability regarding populations and outcomes. Lung deposition rates varied across devices: 8%–53% for pMDIs, 7%-69% for DPIs, and 39%–67% for the SMI. The aerosol exit velocity was high with pMDIs (more than 3 m/s), while it is much slower (0.84–0.72 m/s) with the SMI. In general, pMDIs produce large-sized particles (1.22–8 μm), DPIs produce medium-sized particles (1.8–4.8 µm), and 60% of the particles reach an aerodynamic diameter <5 μm with the SMI. All inhalation devices reach central and peripheral lung regions, but the SMI distribution pattern might be better compared with pMDIs. DPIs’ intrinsic resistance is higher than that of pMDIs and SMI, which are relatively similar and low. Depending on the DPI, the minimum flow inspiratory rate required was 30 L/min. pMDIs and SMI did not require a high inspiratory flow rate. CONCLUSION: Lung deposition and inspiratory flow rate are key factors when selecting an inhalation device in COPD patients.