Sinthia Bosnic-Anticevich, Henry Chrystyn, Richard W Costello, Myrna B Dolovich, Monica J Fletcher, Federico Lavorini, Roberto Rodríguez-Roisin, Dermot Ryan, Simon Wan Yau Ming, David B Price

Patients with COPD may be prescribed multiple inhalers as part of their treatment regimen, which require different inhalation techniques. Previous literature has shown that the effectiveness of inhaled treatment can be adversely affected by incorrect inhaler technique. Prescribing a range of device types could worsen this problem, leading to poorer outcomes in COPD patients, but the impact is not yet known. To compare clinical outcomes of COPD patients who use devices requiring similar inhalation technique with those who use devices with mixed techniques. A matched cohort design was used, with 2 years of data from the Optimum Patient Care Research Database. Matching variables were established from a baseline year of follow-up data, and two cohorts were formed: a "similar-devices cohort" and a "mixed-devices cohort". COPD-related events were recorded during an outcome year of follow-up. The primary outcome measure was an incidence rate ratio (IRR) comparing the rate of exacerbations between study cohorts. A secondary outcome compared average daily use of short-acting beta agonist (SABA). The final study sample contained 8,225 patients in each cohort (mean age 67 [SD, 10], 57% males, 37% current smokers). Patients in the similar-devices cohort had a lower rate of exacerbations compared with those in the mixed-devices cohort (adjusted IRR 0.82, 95% confidence interval [CI] 0.80-0.84) and were less likely to be in a higher-dose SABA group (adjusted proportional odds ratio 0.54, 95% CI 0.51-0.57). COPD patients who were prescribed one or more additional inhaler devices requiring similar inhalation techniques to their previous device(s) showed better outcomes than those who were prescribed devices requiring different techniques.