title: The inhalation characteristics of patients when they use different dry powder inhalers.
abstract: BACKGROUND
  The characteristics of each inhalation maneuver when patients use dry powder inhalers (DPIs) are important, because they control the quality of the emitted dose.
  
  
  METHODS
  We have measured the inhalation profiles of asthmatic children [CHILD; n=16, mean forced expiratory volume in 1 sec (FEV1) 79% predicted], asthmatic adults (ADULT; n=53, mean predicted FEV1 72%), and chronic obstructive pulmonary disease (COPD; n=29, mean predicted FEV1 42%) patients when they inhaled through an Aerolizer, Diskus, Turbuhaler, and Easyhaler using their "real-life" DPI inhalation technique. These are low-, medium-, medium/high-, and high-resistance DPIs, respectively. The inhalation flow against time was recorded to provide the peak inhalation flow (PIF; in L/min), the maximum pressure change (ΔP; in kPa), acceleration rates (ACCEL; in kPa/sec), time to maximum inhalation, the length of each inhalation (in sec), and the inhalation volume (IV; in liters) of each inhalation maneuver.
  
  
  RESULTS
  PIF, ΔP, and ACCEL values were consistent with the order of the inhaler's resistance. For each device, the inhalation characteristics were in the order ADULT>COPD>CHILD for PIF, ΔP, and ACCEL (p<0.001). The results showed a large variability in inhalation characteristics and demonstrate the advantages of ΔP and ACCEL rather than PIFs. Overall inhaled volumes were low, and only one patient achieved an IV >4 L and ΔP >4 kPa.
  
  
  CONCLUSIONS
  The large variability of these inhalation characteristics and their range highlights that if inhalation profiles were used with compendial in vitro dose emission measurements, then the results would provide useful information about the dose patients inhale during routine use. The inhalation characteristics highlight that adults with asthma have greater inspiratory capacity than patients with COPD, whereas children with asthma have the lowest. The significance of the inhaled volume to empty doses from each device requires investigation.
authors.affiliation: 1 Department of Pharmacy, School of Applied Sciences, University of Huddersfield , Huddersfield, HD1 3DH, United Kingdom .
authors.forename: Wahida
authors.initials: W
authors.lastname: Azouz
authors.forename: Philip
authors.initials: P
authors.lastname: Chetcuti
authors.forename: Harold S R
authors.initials: HS
authors.lastname: Hosker
authors.forename: Dinesh
authors.initials: D
authors.lastname: Saralaya
authors.forename: John
authors.initials: J
authors.lastname: Stephenson
authors.forename: Henry
authors.initials: H
authors.lastname: Chrystyn
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001249:Asthma / Q000503:physiopathology*; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D002648:Child; D002675:Child, Preschool; D058995:Dry Powder Inhalers; D004739:England; D004867:Equipment Design; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate; D011208:Powders; D011312:Pressure; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D013647:Task Performance and Analysis; D013997:Time Factors; D014797:Vital Capacity; D055815:Young Adult
chemical_list: D001993:Bronchodilator Agents; D011208:Powders
keywords: COPD; asthma; dry powder inhalers; inhalation profiles; inhaled therapy