Peak inspiratory flow rate measurement in inhaler technique optimisation across inhaler devices

Background: Peak inspiratory flow rate (PIFR) is an important physiological parameter to assess during inhaler technique optimisation (ITO) and inhaler device selection, providing insight into patients’ ability to generate appropriate inspiratory flow for effective medication delivery.

Objectives: To determine the proportion of patients achieving optimal PIFR ranges before and after ITO across inhaler devices using the In-Check G-16 DIAL, and assess the relationship between PIFR ranges and clinical outcomes (self-reported exacerbation frequency, ACQ-6 and CAT scores).

Methods: 586 adult inhaler users (58.4% female) were recruited. PIFR was measured pre- and post-ITO by healthcare professionals using the In-Check G-16 DIAL. Optimal and suboptimal PIFR ranges were interpreted using the device's numerical and colour-coded display. Statistical analysis compared PIFR before and after ITO for each device and clinical outcomes across optimal and suboptimal pre-ITO PIFR.

Results: For pMDI, soft mist, and breath-actuated inhalers (n = 249), only 34.1% achieved the optimal PIFR of 20-60 L/min pre-ITO, increasing to 89.8% post-ITO. For DPI devices, 43% achieved a PIFR of >60 L/min pre-ITO (adjusted to >30 L/min for high-resistance devices), increasing to 96.1% post-ITO. No significant difference in clinical outcomes was found between PIFR ranges across all devices (p > 0.05).

Conclusions: PIFR assessment is important for optimising inhaler technique, as many users initially fail to achieve optimal flow rates. Post-ITO, most users can attain optimal PIFR. For metered-dose inhalers, focus should be on decreasing flow rates or considering a switch to DPIs. PIFR does not appear to be a significant predictor of clinical outcomes across devices.