title: Prevalence and COPD phenotype for a suboptimal peak inspiratory flow rate against the simulated resistance of the Diskus® dry powder inhaler.
abstract: BACKGROUND
  Patients who exhibit a suboptimal peak inspiratory flow rate (PIFR) against the resistance (resist) of a dry powder inhaler (DPI) may not be able to effectively inhale the medication into their lower respiratory tract. PIFRresist was measured using the In-Check DIAL(®) to simulate the resistance of the Diskus(®) DPI in patients with chronic obstructive pulmonary disease (COPD) who were ≥ 60 years of age and had forced expiratory volume in 1 sec (FEV1) of ≤ 50% predicted. Our objectives were to: establish the prevalence of a suboptimal PIFRresist (< 60 L/min) in this population; identify a phenotype of patients with COPD who exhibit a suboptimal PIFRresist; and assess test-retest reliability of PIFRresist.
  
  
  METHODS
  PIFRresist and inspiratory capacity (IC) were measured after spirometry was performed in patients with advanced COPD. Repeat measurement of PIFRresist was performed in a subset of patients who returned for scheduled follow-up appointments.
  
  
  RESULTS
  The prevalence of a PIFRresist of <60 L/min was 19% among 213 patients. The clinical phenotype of these 41 patients included predominantly female gender (80%), shorter height, and lower values for forced vital capacity (FVC) and IC as percentage predicted compared with the 172 patients with PIFRresist of > 60 L/min. Multivariate regression analysis performed on all patients demonstrated that age, gender, height, FVC % predicted, and IC % predicted were independent predictors of PIFRresist (R(2)=36%). Repeat testing showed no difference between the PIFRresist values.
  
  
  CONCLUSIONS
  Approximately one out of five patients with advanced COPD and ≥ 60 years of age exhibited a suboptimal PIFRresist against the Diskus. For the first time, a clinical phenotype of such patients with a suboptimal PIFRresist was identified. It is reasonable to measure a patient's PIFR against the simulated resistance of a specific DPI if there is concern about clinical benefit using the dry powder medication.
authors.affiliation: Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA. Donald.a.mahler@hitchcock.org
authors.forename: Donald A
authors.initials: DA
authors.lastname: Mahler
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Waterman
authors.forename: Alex H
authors.initials: AH
authors.lastname: Gifford
mesh_terms: D000367:Age Factors; D000368:Aged; D001827:Body Height; D015331:Cohort Studies; D016503:Drug Delivery Systems; D058995:Dry Powder Inhalers; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010641:Phenotype; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012737:Sex Factors; D013147:Spirometry; D014797:Vital Capacity / Q000502:physiology*