Maximal forced inspiratory flow dynamics and acute exacerbation in COPD patients with exacerbation history.

Background: Chronic Obstructive Pulmonary Disease (COPD) is a significant global health burden characterized by progressive airflow obstruction and frequent exacerbations. Traditionally, COPD severity has been assessed using expiratory flow measurements like FEV1. However, the role of inspiratory flow, specifically maximal forced inspiratory flow (FIFmax), in predicting exacerbation risk is gaining attention.

Methods: This retrospective cohort study evaluated COPD patients with a history of exacerbations, receiving inhaled therapy. The eligible patients were followed up for 3 years with spirometric assessments. Patients were categorized into quartiles based on the annual change in FIFmax, from the greatest decrease (Q1) to the greatest increase (Q4). Primary outcome was acute exacerbation, stratified by severity as moderate-to-severe and severe exacerbation.

Results: A total of 180 patients were followed up for 3 years. While a greater increase in FIFmax was linearly associated with lower rates of both moderate-to-severe and severe exacerbations (P-value for trend <0.001 for both), time-to-event analysis revealed no significant association between FIFmax changes and moderate-to-severe exacerbations. In contrast, a significant association was observed with severe exacerbations (Log-Rank P-value=0.005). Even after adjusting for confounders, FIFmax remained an independent predictor of severe exacerbations (Q3: hazard ratio=0.506 [95% confidence interval=0.306-0.836], P-value=0.008; Q4: hazard ratio=0.491 [95% confidence interval=0.291-0.830], P-value=0.008).

Conclusions: Changes in FIFmax were not significantly associated with moderate-to-severe exacerbations but were related with a reduced risk of severe exacerbations in COPD patients receiving inhaled therapy. These findings suggest that FIFmax may serve as a valuable prognostic marker for severe exacerbations in high-risk COPD patients.