The impact of inspiratory effort on inspiratory flow through Turbuhaler in asthmatic patients.

To investigate the impact of the inhalation effort on the peak inspiratory flow through Turbuhaler, 100 asthmatics having a wide range of asthma severity (baseline forced expiratory volume in one second 28-127% of predicted normal) were studied. Each patient inhaled through four modifications of empty Turbuhaler inhalers, using first a "deep" inhalation and then a "forceful and deep" inhalation manoeuvre. Peak inspiratory flow increased by an average of 20% using a "forceful and deep" as compared to a "deep" inhalation, with a markedly higher increase for the patients who had a low peak inspiratory flow using the deep inhalation. Virtually all patients (97-100%) attained a peak inspiratory flow > or = 40 L x min(-1) after a "forceful and deep" inhalation. This study demonstrates that instructing the patient to take a "forceful and deep" inhalation optimizes the use of Turbuhaler. Irrespective of asthma severity, the vast majority of patients could attain a sufficiently high peak inspiratory flow with a "forceful and deep" inhalation.