Usability of inhaler devices: a parameter currently misused.

Inhalation represents the most convenient route for delivering respiratory drugs. Delivery systems showed a huge technological progress and several pocket inhalers had been engineered over the last decades for clinical use. Despite the growing technological efforts aimed to simplify the inhalation procedures and optimize the therapeutic outcomes, the effectiveness of drug inhalation through inhalers still represents a major challenge in respiratory medicine. Patients may actually incur in different types of critical errors when using all inhalers and are not capable to inhale throughout all devices equally well. Therefore, the choice of the most suitable and convenient device to prescribe still is a critical issue in real life. Usability is the only comprehensive parameter consenting the effective and objective assessment of pocket inhalers' performance, and allowing their objective comparison and ranking. Unpredictable discrepancies are in fact easily detectable between inhalers (even belonging to the same class) in terms of Usability, independently of the patient's awareness. The reasons were described and discussed for each class of inhalers presently available. Usability is a multidimensional parameter that is much more multifaceted and complex than usually presumed. Usability takes origin from the integrated, balanced and objective assessment of the role played by several factors from different domains, such as: factors related to patient's beliefs, to patients' behavioural components, to device engineering and to the overall cost. Usability is the key parameter for assessing and optimizing the appropriateness of any inhalation treatment through whatever device. Usability would also represent a key investigational instrument for supporting the future development of -innovative and more performing inhaler devices objectively.