Does mixing inhaler devices lead to unchecked inhaler technique errors in patients with COPD? Findings from the cross-sectional observational MISMATCH study

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) may be prescribed multiple inhalers that require different techniques for optimal performance. Mixing devices has been associated with poorer COPD outcomes suggesting that it leads to inappropriate inhaler technique. However, empirical evidence is lacking. AIMS: Compare the nature and frequency of dry powder inhaler (DPI) technique errors in patients with COPD using (1) a single DPI or (2) mixed-devices (a DPI and pressurised metered dose inhaler (pMDI)). METHODS: Data from the PIFotal study-a cross-sectional study on Peak Inspiratory Flow in patients with COPD using a DPI as maintenance therapy, capturing data from 1434 patients on demographic characteristics, COPD health status and inhaler technique-were used to select 291 patients using mixed-devices. Frequency matching based on country of residence and DPI device type was used to select 291 patients using a DPI-only for comparison. Predetermined checklists were used for the evaluation of DPI video recordings and complemented with additional errors that were observed in ≥10%. Error proportions were calculated for the (1) individual and total number of errors, (2) number of critical errors and (3) number of pMDI-related errors. RESULTS: The study sample contained 582 patients (mean (SD) age 69.6 (9.4) years, 47.1% female). DPI technique errors were common, but not significantly different between the groups. The majority of patients made at least one critical error (DPI-only: 90.7% vs mixed-devices: 92.8%). Proportions of total, 'pMDI-related' and critical errors did not significantly differ between the groups. CONCLUSION: The nature and frequency of inhaler technique errors did not substantially differ between patients prescribed with a single DPI and mixed-devices. Currently, 'pMDI-related errors' in DPI use are not accounted for in existing checklists. TRIAL REGISTRATION NUMBER: ENCEPP/EUPAS48776.