Changes in device-matched peak inspiratory flow after bedside inhaler coaching and factors associated with residual suboptimal flow: a retrospective observational study

Background Peak inspiratory flow rate (PIFR) is a critical determinant of inhaler-device compatibility, particularly when assessed under resistance conditions matching the prescribed inhaler. However, changes in device-matched PIFR patterns after inhaler coaching and factors associated with persistent abnormalities remain insufficiently characterized among hospitalized patients with chronic airway diseases. Methods We conducted a retrospective single-center observational study of hospitalized adults with chronic obstructive pulmonary disease, asthma, or asthma–COPD overlap who underwent routine device-matched PIFR assessment between July 2024 and December 2025. PIFR was measured using the In-Check DIAL G16 before and after standardized bedside coaching under resistance settings matched to the prescribed inhaler. Logistic regression analyses were performed to identify factors associated with persistent post-coaching PIFR abnormalities. Results Among 286 patients, the distribution of device-matched PIFR shifted substantially toward the device-specific optimal PIFR range after bedside assessment and coaching. The proportion of patients within the optimal PIFR range increased from 42.3% to 89.2%, whereas insufficient and excessive PIFR decreased from 25.2% to 6.9% and from 32.5% to 3.9%, respectively (all P < 0.001). Lower body mass index was independently associated with persistent insufficient PIFR, whereas ICS-containing therapy was also associated with this residual abnormality. Persistent excessive PIFR was uncommon and primarily observed among patients using pMDI/SMI devices. Conclusion Device-matched PIFR assessment combined with individualized coaching was associated with a substantial shift toward the device-specific optimal PIFR range among hospitalized patients with chronic airway diseases. However, persistent insufficient PIFR remained in a subset of patients and was associated with lower BMI and ICS-containing therapy, suggesting that these factors may help identify patients who warrant closer reassessment of inhaler–device compatibility.