Prevalence and predictors of suboptimal peak inspiratory flow values with metered-dose dry powder inhalers in patients with asthma and chronic obstructive pulmonary disease

Background. A key requirement for effective dry powder inhaler (DPI) use is adequate patient inspiratory effort, measurable through peak inspiratory flow (PIF). Aim. To assess the prevalence of suboptimal PIF values, and identify factors significantly affecting PIF in pulmonary disease (COPD) and asthma outpatients. Materials and methods. The study enrolled asthma and COPD patients using DPIs for maintenance therapy. PIF was measured using In-Check DIAL G16® at resistance levels matching each patient's DPI, both before and after proper inhalation technique training. Clinical and functional parameters were evaluated to identify predictors of suboptimal PIF. Results. The study included 61 asthma and 30 COPD patients. Baseline suboptimal PIF rates were 34% (asthma) and 63% (COPD). After training, these decreased significantly to 10% (asthma) and 23% (COPD); p 0.0001. Key limiting factors for achieving optimal PIF were age ≥ 60 years, FVC ≤ 70% predicted, and FEV1 ≤ 45% predicted. Conclusion. Many patients had insufficient inspiratory flow for effective DPI use due to technique errors or age/functional limitations. Pre-prescription PIF measurement objectively evaluates DPI suitability and enhances treatment efficacy.