Home assessment of peak inspiratory flow through the Turbohaler in asthmatic patients.

BACKGROUND The efficacy of dry powder inhalers depends on the patient's inspiratory flow. Drug delivery from the Turbohaler (Turbuhaler in some countries), a multidose powder inhaler, is optimal at flows of > 40 l/min. The aim of this study was to investigate the peak inspiratory flow that can be generated by asthmatic patients through the budesonide Turbohaler (PIFTBH) during maintenance treatment at home. METHODS Thirty asthmatic patients, consecutively recruited from the outpatient clinic, inhaled their maintenance dose of 800 (n = 16) or 1600 micrograms/day (n = 14) for two months or one month, respectively. The Turbohaler was connected to a modified Vitalograph Compact installed at home to obtain printed PIFTBH values for all inhalations. Peak expiratory flow (PEF) was measured twice daily. RESULTS Flows were remarkably constant with individual mean PIFTBH values ranging from 55 l/min to 95 l/min. Only 13 of the 5248 PIFTBH recordings taken at home (three patients) were < 40 l/min and all were > 30 l/min. Weekly mean morning PEF values ranged from 114 l/min to 733 l/min. PIFTBH values could not be accurately predicted from lung function parameters in individual patients. CONCLUSIONS In a group of stable asthmatic patients inspiratory flow rates rarely fell below the 40 l/min needed to operate a Turbohaler.