Dry-powder inhalers in patients with persistent airflow limitation: usability and preference.

Background: Inhalation devices represent per sé critical factors because they can affect the therapeutic outcomes independently of the drug used. The role of patients' usability and preference (PUP) for Dry Powder Inhalers (DPIs) is high indeed because they can influence the extent of the adherence to treatment and the therapeutic outcomes. Aim of the study was to assess and compare the PUP of three different DPIs in out-patients with persistent airflow limitation due to asthma or COPD.

Methods: The PUP of three different DPIs (Breezhaler; Genuair; Handihaler) were investigated by means of the Handling Questionnaire in out-patients with persistent airflow limitation needing an inhalation therapy. Patients had to report their preference before and after the nurse's instruction on the handling of each device. The nurse had also to note the critical steps during the patient's procedure for actuation; to count the number of attempts needed for actuating the device properly, and to measure the time (in sec.) required for these procedures. Data were collected up to three attempts per device.

Statistics: Welch test was used for normal distributed variables, while the Wilcoxon test for not normal distributed variables. The χ (2) test and the ANOVA test were also used. Univariate and multivariate regressions were also performed in order to investigate the effect of patients' characteristics and of technical differences of each device on their proper use.

Results: Three hundred thirty-three consecutive out-patients (age range 55-58 years, and well matched for gender), with persistent airway limitation of different severity were investigated, suffering from bronchial asthma (n = 175) or from chronic obstructive pulmonary disease (COPD) (n = 158). In particular, 127 patients (38 %) tested the three DPIs, while 110 (33 %) tested Breezhaler and Genuair, and 96 (29 %) Breezhaler and Handihaler. More than 50 % of patients who tested all devices preferred the Genuair and perceived this device as the easiest to use. The nurse's judgement confirmed their opinion. When compared to the other two DPIs, Genuair proved the least problematic either according to the patients' judgement and to the nurse's opinion. Mean number of attempts aimed to achieving the first proper actuation was lower with Genuair than with Breezhaler and Handihaler (1.5 vs 2.5-2.6, p < 0.0001). Finally, Genuair also proved the easiest to use and the least problematic according to the nurse judgement (0.0001), the most easily learned (0.0001), and that one with a successful rate of more than 56 % at the first attempt. Breezhaler and Handihaler needed an average of about one additional attempt to be used properly (p < 0.0001), and their usability proved significantly more difficult (OR of successful rate between 0.15 and 0.17, p < 0.001). In general, older patients needed more attempts to perform their first proper inhalation; their successful rate was lower, and they needed more time to learn how to use devices properly: with Genuair these differences were minimized.

Conclusions: The possibility of grading objectively the performance of different DPIs in terms of their usability and therapeutic convenience in daily life represents a crucial operational opportunity to pursue. To note that a substantial discrepancy exists between the patients' belief "at glance" and the patients' effective usability with can be registered with some devices. From a general point of view, devices requiring less manual actions for their actuation confirmed their better usability and proper handling after less attempts. In particular, Genuair came out as the most preferred DPI also when several different aspects of preference and usability are assessed objectively and compared.