The contribution of patients' lung function to the inspiratory airflow rate achievable through a DPIs' simulator reproducing different intrinsic resistance rates

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.

Lung Function Can Predict the Expected Inspiratory Airflow Rate through Dry Powder Inhalers in Asthmatic Adolescents

Several factors affect drug delivery from dry powder inhalers (DPIs). Some are related to patient’s physiological characteristics, while others depend on DPIs’ technical aspects. The patient’s inspiratory airflow rate (IAR) affects the pressure drop and the turbulence needed to disaggregate the powder inside a DPI. The present study investigated whether lung function limitations occurring in asthmatic adolescents affect their IAR when inhaling through a DPI simulator. Eighteen consecutive adolescents with asthma were recruited, and IAR was randomly assessed at low-, mid-, and high-resistance regimens. A multiple logistic model was developed to evaluate the association of patients’ lung function characteristics and devices’ resistance with the probability to achieve the expected IAR (E-IAR). The mean value of E-IAR achieved seemed to be sex- and age-independent. Low- and high-resistance regimens were less likely to consent the E-IAR level (odds ratio [OR] = 0.035 and OR = 0.004, respectively). Only the basal residual volume and the inspiratory resistance, but not the Forced Expiratory Volume in 1 s (FEV1), seemed to affect the extent of IAR in asthmatic adolescents (OR = 1.131 and OR = 0.290, respectively). The results suggest that the assessment of current lung function is crucial for choosing the proper DPI for asthmatic adolescents.

A Bayesian Framework to Assess the Usability of Dry Powder Inhalers in a Cohort of Asthma Adolescents in Italy

The useability of DPIs (dry powder inhalers) depends on several factors that are influenced by the patients’ subjectivity and objectivity. The short-form global usability score (S-GUS), a specific tool for the quick ranking and comparison in real life of an inhaler’s usability, was used to investigate six of the most prescribed DPIs (Breezhaler, Diskus, Ellipta, Nexthaler, Spiromax, and Turbohaler) in consecutive asthma patients aged <18 years. A Bayesian indirect comparison (IC) was carried out to merge all pairwise comparisons between the six DPIs. Thirty-three subjects participated: eighteen tested Breezhaler, Spiromax, Nexthaler, and Ellipta simultaneously, while fifteen tested Breezhaler, Spiromax, Diskus, and Turbohaler. The estimates of the S-GUS, by the IC model, allowed us to rank the DPIs by their degree of usability: Ellipta, Diskus, and Spiromax were classified as “good to pretty good” (S-GUS > 15), while Spiromax, Turbohaler, and Breezhaler were classified as “insufficient” (S-GUS < 15). The multidomain assessment is recommended in asthma adolescents in order to approximate the effective usability of different DPIs as best as possible. The S-GUS proves particularly suitable in current clinical practice because of the short time required for its use in adolescents.