Prospective Evaluation of Exacerbations Associated with Suboptimal Peak Inspiratory Flow Among Stable Outpatients with COPD

PURPOSE: A suboptimal peak inspiratory flow (PIF) against a dry powder inhaler (DPI) may result in ineffective inhalation of medications, which may affect outcomes. The primary objective of this study was to examine the association between PIF status and COPD exacerbations among outpatients with moderate to very severe COPD. PATIENTS AND METHODS: This was a prospective, observational study of patients from 7 US outpatient centers. PIF was measured using an inspiratory flow meter (In-Check™ DIAL G16) set to medium low resistance. Patients were classified by suboptimal (<60 L/min) or optimal PIF (≥60 L/min). The primary outcome was the proportion of patients with moderate/severe COPD exacerbations collected by medical record review over 12 months. Secondary outcomes were time to first exacerbation and mortality. RESULTS: Of 474 patients screened, 38.8% had suboptimal PIF, and 71 patients with optimal PIF were excluded from the study. The enrolled sample included 184 and 219 patients with suboptimal and optimal PIF, respectively. Suboptimal PIF was associated with shorter stature (66.6±4.1 vs 67.8±3.8 inches, P = 0.002), female sex (45.1 vs 34.7%, P = 0.033), Black race (27.2 vs 11.0%, P < 0.001), and greater symptom burden (CAT: 22.3±7.7 vs 19.0±7.0, P < 0.001; mMRC: 2.0±1.1 vs 1.7±1.1, P = 0.003). The proportion of patients with COPD exacerbations at 12 months was not significantly different (29.3 vs 27.9%, P = 0.751). Suboptimal PIF was associated with shorter time to first COPD exacerbation (3.8±2.7 vs 4.9±3.0 months, P = 0.048). The mortality rate at 12 months was higher in the suboptimal cohort but not significantly different (6.5 vs 2.8%, P = 0.073). CONCLUSION: Over one-third of outpatients with stable moderate to very severe COPD had a suboptimal PIF against a medium low resistance DPI. The phenotype of suboptimal PIF was short stature, female, and Black. Suboptimal PIF status was associated with shorter time to moderate/severe COPD exacerbations compared with optimal PIF.