LAUSR

Background: The small airways (SA) are the major site of airflow limitation in COPD. Yet, most inhaler devices do not deliver their drug to reach this lung region, hence contributing to ongoing poor COPD control. Tiotropium bromide (Tio) is an established bronchodilator in COPD management with delivery from the dry powder inhaler (DPI) HandiHaler (HH). More recently, the slow mist inhaler (SMI) Respimat (RM) was introduced, with fine aerosol droplets that can potentially target the SA. Aim: We compared the effect of the same drug, Tio, delivered from two different devices, DPI vs. SMI, on physiological measures of SA to determine whether the inhaler device was important in targeting drug to the SA. Methods: Mild-moderate COPD patients (n=44, mean FEV1= 67%pred) already on DPI-HH (18µg daily), underwent a pragmatic clinical study: Day 0: Patients’ DPI-HH technique was observed and optimally corrected, then patients continued DPI-HH for 14 days. Day 14: patients were changed to SMI-RM and trained, then maintained SMI-RM (5µg daily) for 14 days. At each visit, large (spirometry) and small (impulse oscillometry, IOS) airway function was recorded. Results: Only SMI-RM significantly improved SA function (IOS resistance (R) R5-R20, R5, and IOS reactance (X) X5) (Table). Interestingly, SMI-RM also significantly improved large airway FEV1, R20. Conclusions: This is the first study to show the inhaler device matters in targeting drug to the site of airflow limitation in COPD. SMI-RM significantly improved SA function over and above that of DPI-HH.*=p<0.001