Daily inhaled flow profiles and drug release from dry powder inhalers in patients with bronchial asthma.

Background: Inhalation flow profiles may affect particle release from dry powder inhalers (DPIs). Currently available measures include a limited number of laboratory-measured parameters such as peak inhalation flow (PIF) and inhaled volume (inhV). We aimed to investigate whether parameters obtained under such conditions are valid in real-world settings and determine the effective inhalation profile.

Method: We included seven asthmatics without recent deterioration and regularly inhaling Turbuhaler® or Diskus®. Daily inhalation profiles and particle release from either DPI were measured at home using a newly designed handy analyzer (real-life inhalation events recorder [RLEFR]), for ≥2 weeks. Inhalation pressure drop and signals of particle release during each inhalation were recorded.

Results: All patients inhaled daily with similar patient-specific profiles. The mean PIF and inhV were 91.9-31.6 L/min and 0.84-2.05 L, respectively. PIFs were smaller than those obtained in previous laboratory studies, and only one patient exceeded inhV of 2.0 L. The mean flow acceleration and particle emission were 39-571 L/min/s and 0.37-1.54 s, respectively. Particle release was sporadic in one Turbuhaler® user whose PIF was 31.6 L/min, appearing at 1.55 s of inhalation. Particle release from Turbuhaler® appeared to be PIF-dependent, but that from Diskus® was not.

Conclusion: Inhalation flow profile measured at home is highly reproducible, but tends to be weaker and shorter than that measured in the laboratory. The results confirm that rapid inhalations from the start are required when using a DPI. RLEFR is a promising device for patient education and clinical studies.

Trial Registration Number: UMIN000045193.