title: Minimal inspiratory flow from dry powder inhalers according to a biphasic model of pressure vs. flow relationship.
abstract: Inhalation therapy using the dry powder inhaler (DPI) is now the first choice for obstructive pulmonary diseases. We previously measured relationships between inspiratory pressure (PI) and flow rate of almost all of the DPIs available in Japan, and described an importance of inspiratory efforts. In the present study, we further analyzed the data obtained in the previous study. Although there were linear relationships between PI and flow2, the slope became steeper when PI was less than a certain value (critical PI, existed between 15-20 cmH2O). When PI was less than critical PI, linear rather than parabolic regression between PI and flow yielded better fits (r > 0.90, p < 0.001). Inspiratory flows at the critical PI were 53.9 (Diskus), 65.8 (Diskhaler), 45.9 (Turbuhaler for Pulmincort), 48.6 (Turbuhaler for Symbicort) and 38.0 l/min (Twisthaler). These findings suggested that flow through the DPI becomes laminar rather than turbulent flow in the range below critical PIs. We suggest that patients should inhale from the DPIs with inspiratory pressure higher than critical PI.
authors.affiliation: Department of Cardiovascular Surgery, Tokai University Hachioji Hospital, Tokyo, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kanabuchi
authors.forename: Tetsuri
authors.initials: T
authors.lastname: Kondo
authors.forename: Toshimori
authors.initials: T
authors.lastname: Tanigaki
authors.forename: Sakurako
authors.initials: S
authors.lastname: Tajiri
authors.forename: Naoki
authors.initials: N
authors.lastname: Hayama
authors.forename: Yoko
authors.initials: Y
authors.lastname: Takahari
authors.forename: Kayoko
authors.initials: K
authors.lastname: Iwao
mesh_terms: D001249:Asthma / Q000188:drug therapy / Q000503:physiopathology; D058995:Dry Powder Inhalers / Q000706:statistics & numerical data; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008954:Models, Biological; D011208:Powders; D011312:Pressure; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy / Q000503:physiopathology; D012044:Regression Analysis; D012138:Respiratory Therapy / Q000295:instrumentation* / Q000706:statistics & numerical data; D012212:Rheology
chemical_list: D011208:Powders