RESUMO
OBJECTIVE: Because dry powder inhalers (DPI) aerosolize agents by means of inspiration of patients themselves, inspiratory resistance of DPI is an important factor for increasing inhalation efficiency. Therefore, we measured inspiratory resistance of DPI of agents for asthma control. METHODS: Using Flow/Volume Simulator, when setting flow rates at 6, 30, 60, 90, and 120L/min, we read off suction pressures and find inspiratory resistances by calculation (=suction pressure/flow rate) at each flow rate. RESULTS: In all DPI, inspiratory resistance increases with the increasing flow rate. To maintain flow rate of 60L/min, suction pressure of around 20-cmH2O for Diskus(®) and Ellipta(®), between 35- and 45-cmH2O for Turbuhaler (®), and about 60-cmH2O for Twisthaler(®) were needed. CONCLUSION: It is suggested that we should instruct patients to inhaler DPI based on inspiratory resistance of the DPI.