Clinical Implications of Peak Inspiratory Flow in COPD: Post Hoc Analyses of the TRONARTO Study

Background: In patients with COPD, inhalation ability should be assessed when considering inhaler choice. To evaluate whether the soft mist inhaler (SMI) is suitable for COPD patients irrespective of inhalation ability, the TRONARTO study investigated the efficacy of dual long-acting bronchodilator therapy delivered via the Respimat^® SMI on lung function in patients with COPD stratified by inhalation ability. Tiotropium/olodaterol delivered via the SMI was effective both in patients with peak inspiratory flow (PIF) <60 L/min and PIF ≥60 L/min, measured against medium-low resistance.

Methods: This congress compilation summarizes post hoc analyses from the TRONARTO study presented at the annual American Thoracic Society 2022 and European Respiratory Society 2022 meetings. These analyses evaluated PIF in over 200 patients, with PIF measurements taken daily at home for 4 weeks, and in the clinic at baseline, Weeks 2 and 4.

Results: Overall, 57.9% of patients had a PIF range (difference between lowest and highest PIF measurements) <20 L/min (12.4% of patients had PIF range <10 L/min). At-home PIF range decreased over the study period, suggesting that inhaler training/repeated PIF measurements may help to make patients' inspiratory effort more consistent. Some patient characteristics correlated with lower PIF (female gender, shorter stature, more severe disease, worse airflow obstruction) and lower PIF range (more severe disease). PIF measurements differed between medium-low and high-resistance settings, highlighting the importance of measuring PIF at the resistance of a patient's inhaler. PIF correlated poorly with spirometry measurements.

Conclusion: As indicated in COPD management guidelines, choice of inhaler is essential to optimize pharmacologic therapies for COPD. Poor inspiratory ability should be viewed as a treatable trait that can help to inform inhaler choice. Inhaler training and consideration of PIF (if patients use a dry powder inhaler) can reduce patient-to-inhaler mismatch, with potential consequences for health status and exacerbation risk.