ASSOCIATION BETWEEN LOW PEAK INSPIRATORY FLOW RATE AND ACUTE EXACERBATION OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN RECENTLY HOSPITALIZED PATIENTS

Abstract

Introduction: Peak inspiratory flow rate (PIFR) is an important determinant of effective drug delivery with dry powder inhalers in patients with chronic obstructive pulmonary disease (COPD). Reduced PIFR is frequently observed following acute exacerbations of COPD (ECOPD), but its role in predicting early post-discharge re-exacerbation remains incompletely defined.

Methods: This prospective cohort study enrolled patients aged ≥40 years who were hospitalized for ECOPD at a tertiary hospital in Thailand between October 2024 and June 2025. PIFR was measured at hospital discharge using the In-Check Dial G16 device (Clement Clarke International, Harlow, UK) configured to a medium-resistance DPI setting. Suboptimal PIFR was defined as <60 L/min. The primary outcome was time to first moderate-to-severe COPD re-exacerbation within 56 days, evaluated by Kaplan–Meier and Cox proportional hazards analyses. The secondary outcome was the incidence of moderate-to-severe re-exacerbation within 56 days, evaluated by logistic regression with modified Poisson regression as a sensitivity analysis.

Results: Of 41 enrolled patients, 36 were included in the final analysis (mean age 66.4 years; all male), of whom 17 (47.2%) had suboptimal PIFR at discharge. During 56 days of follow-up, moderate-tosevere re-exacerbations occurred in 35.3% of patients with PIFR <60 L/min, compared with 5.3% in those with PIFR ≥60 L/min. Time-to-event analysis demonstrated a higher and earlier risk of re-exacerbation in the suboptimal PIFR group (log-rank p=0.024), with an adjusted hazard ratio of 13.52 (95% CI 1.14–159.93). Schoenfeld residuals confirmed the proportional hazards assumption. For the 56-day secondary outcome, suboptimal PIFR was associated with increased odds of re-exacerbation in univariable logistic regression (OR 9.82, 95% CI 1.04–92.78; p=0.046); the corresponding unadjusted risk ratio from modified Poisson regression was 6.71 (95% CI 0.90–50.22; p=0.064). PIFR improved over time in the overall cohort; however, patients who experienced re-exacerbation showed persistently lower or unstable PIFR trajectories.

Conclusion: Suboptimal PIFR at hospital discharge was associated with an increased risk of early COPD re-exacerbation. Assessment of PIFR may help identify patients at higher risk during the post-discharge period and support more individualized inhaler management strategies.