Effect of inhaler design variables on paediatric use of dry powder inhalers

Design, development, and technical considerations for dry powder inhaler devices

The dry powder inhaler (DPI) stands out as a highly patient-friendly and effective pulmonary formulation, surpassing traditional and other pulmonary dosage forms in certain disease conditions. The development of DPI products, however, presents more complexities than that of other dosage forms, particularly in device design and the integration of the drug formulation. This review focuses on the capabilities of DPI devices in pulmonary drug delivery, with a special emphasis on device design and formulation development. It also discusses into the principles of deep lung particle deposition and device engineering, and provides a current overview of the market for DPI devices. Furthermore, the review highlights the use of computational fluid dynamics (CFD) in DPI product design and discusses the regulatory environment surrounding these devices.

Near Elimination of In Vitro Predicted Extrathoracic Aerosol Deposition in Children Using a Spray-Dried Antibiotic Formulation and Pediatric Air-Jet DPI

PURPOSE

This study evaluated the in vitro aerosol performance of a dry powder antibiotic product that combined a highly dispersible tobramycin powder with a previously optimized pediatric air-jet dry powder inhaler (DPI) across a subject age range of 2-10 years.

METHODS

An excipient enhanced growth (EEG) formulation of the antibiotic tobramycin (Tobi) was prepared using a small particle spray drying technique that included mannitol as the hygroscopic excipient and trileucine as the dispersion enhancer. The Tobi-EEG formulation was aerosolized using a positive-pressure pediatric air-jet DPI that included a 3D rod array. Realistic in vitro experiments were conducted in representative airway models consistent with children in the age ranges of 2-3, 5-6 and 9-10 years using oral or nose-to-lung administration, non-humidified or humidified airway conditions, and constant or age-specific air volumes.

RESULTS

Across all conditions tested, mouth-throat depositional loss was < 1% and nose-throat depositional loss was < 3% of loaded dose. Lung delivery efficiency was in the range of 77.3-85.1% of loaded dose with minor variations based on subject age (~ 8% absolute difference), oral or nasal administration (< 2%), and delivered air volume (< 2%). Humidified airway conditions had an insignificant impact on extrathoracic depositional loss and significantly increased aerosol size at the exit of a representative lung chamber.

CONCLUSIONS

In conclusion, the inhaled antibiotic product nearly eliminated extrathoracic depositional loss, demonstrated high efficiency nose-to-lung antibiotic aerosol delivery in pediatric airway models for the first time, and provided ~ 80% lung delivery efficiency with little variability across subject age and administered air volume.

The effects of grid design on the performance of 3D-printed dry powder inhalers

The grid structure is an indispensable part of most dry powder inhalers, but the effects of grid geometry on inhaler performance are rarely reported. This study aims to systemically investigate the influence of grid design on the aerosolization performance of capsule-based inhalers through experiments and computational analysis. In-vitro aerosolization and deposition performance of commercial and 3D-printed customized inhalers with different grid mesh designs were experimentally studied using a Next Generation Impactor (NGI). Flow fields in the inhalers were generated, and average turbulence kinetic energy (TKE) and airstream trajectories were obtained through Computational Fluid Dynamics (CFD) analysis, delineating the effects of the different grid designs. Comparative studies using the commercial inhalers and the 3D-printed inhalers show a slightly better performance for the latter, probably due to the different materials used for the inhalers, confirming the suitability of 3D printing. Experimental results show that intensive grid meshes with a relatively small aperture size are beneficial to enhancing inhaler performance. Computational results illustrate that the intensive grid meshes can reduce vortexed airstreams and increase turbulent kinetic energy at the grids in general, which also supports the experimental results. In summary, inhalers with intensive grid meshes are preferred for capsule-based inhalers to enhance aerosolization performance. These findings have significant implications for the comprehensive understanding of how grid designs influence inhaler performance.

Turning green: the impact of changing to more eco-friendly respiratory healthcare - a carbon and cost analysis of Dutch prescription data

OBJECTIVES

Dry powder inhalers (DPIs) and soft mist inhalers have a substantially lower global warming potential than pressurised metered-dose inhalers (pMDIs). To help mitigate climate change, we assessed the potential emission reduction in CO₂ equivalents when replacing pMDIs by non-propellant inhalers (NPIs) in Dutch respiratory healthcare and estimated the associated cost.

DESIGN

We performed a descriptive analysis of prescription data from two national databases of two independent governmental bodies. First, we calculated the number of patients with chronic obstructive pulmonary disease (COPD) and asthma that were using inhalation medication (2020). Second, we calculated the number and total of daily defined doses of pMDIs and NPIs including DPIs and soft mist inhalers, as well as the number of dispensed spacers per patient (2020). Third, we estimated the potential emission reduction in CO₂ equivalents if 70% of patients would switch from using pMDIs to using NPIs. Fourth, we performed a budget impact analysis.

SETTING

Dutch respiratory healthcare.

PRIMARY AND SECONDARY OUTCOME MEASURES

The carbon footprint of current inhalation medication and the environmental and financial impact of replacing pMDIs with NPIs.

RESULTS

In 2020, 1.4 million patients used inhalers for COPD or asthma treatment. A total of 364 million defined daily doses from inhalers were dispensed of which 49.6% were dispensed through pMDIs. We estimated that this could be reduced by 70% which would lead to an annual reduction in greenhouse gas emission of 63 million kg.CO2 equivalents saving at best EUR 49.1 million per year.

CONCLUSIONS

In the Netherlands, substitution of pMDIs to NPIs for eligible patients is theoretically safe and in accordance with medical guidelines, while reducing greenhouse gas emission by 63 million kg.CO2 equivalents on average and saving at best EUR 49.1 million per year. This study confirms the potential climate and economic benefit of delivering a more eco-friendly respiratory care.

Spray-dried Pneumococcal Membrane Vesicles are Promising Candidates for Pulmonary Immunization

Pneumococcal infections represent a global health threat, which requires novel vaccine developments. Extracellular vesicles are secreted from most cells, including prokaryotes, and harbor virulence factors and antigens. Hence, bacterial membrane vesicles (MVs) may induce a protective immune response. For the first time, we formulate spray-dried gram-positive pneumococcal MVs-loaded vaccine microparticles using lactose/leucine as inert carriers to enhance their stability and delivery for pulmonary immunization. The optimized vaccine microparticles showed a mean particle size of 1-2µm, corrugated surface, and nanocrystalline nature. Their aerodynamic diameter of 2.34µm, average percentage emitted dose of 88.8%, and fine powder fraction 79.7%, demonstrated optimal flow properties for deep alveolar delivery using a next-generation impactor. Furthermore, confocal microscopy confirmed the successful encapsulation of pneumococcal MVs within the prepared microparticles. Human macrophage-like THP-1 cells displayed excellent viability, negligible cytotoxicity, and a rapid uptake around 60% of fluorescently labeled MVs after incubation with vaccine microparticles. Moreover, vaccine microparticles increased the release of pro-inflammatory cytokines tumor necrosis factor and interleukin-6 from primary human peripheral blood mononuclear cells. Vaccine microparticles exhibited excellent properties as promising vaccine candidates for pulmonary immunization and are optimal for further animal testing, scale-up and clinical translation.

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.

Impact of Payor-Initiated Switching of Inhaled Corticosteroids on Lung Function

OBJECTIVES

To evaluate the impact of a payor-initiated formulary change in inhaled corticosteroid coverage on lung function in patients with asthma and on provider prescribing practices. This formulary change, undertaken in August 2016 by a Medicaid payor in Kentucky, eliminated coverage of beclomethasone dipropionate, a metered dose inhaler (MDI), in favor of mometasone furoate, available as MDI and dry powder inhaler (DPI).

STUDY DESIGN

A retrospective chart review was conducted on children with asthma ages 6-18 years covered by the relevant payor from a university-based pediatric practice who were seen before the formulary change (February to July 2016) and after (February to July 2017). Spirometry data from each visit was compared using the paired Student t test.

RESULTS

Fifty-eight patients were identified who were initially on beclomethasone dipropionate and had spirometry available at both visits. Those who switched from an MDI to a DPI (n = 24) saw a decline in median predicted forced expiratory volume in 1 second from 98.5% to 91% (P = .013). A decline was also seen in forced expiratory flow at 25%-75%, from 89.5% predicted to 76% predicted (P = .041). No significant changes were observed in children remaining on an MDI. Seven patients discontinued inhaled corticosteroid therapy.

CONCLUSIONS

This study suggests insurance formulary changes leading to use of a different inhaler device may have a detrimental impact on pediatric lung function, which may be a surrogate measure for overall asthma control. This could be due to a lack of adequate timely educational intervention as well as the inability of some children to use DPIs.

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

Background

The performance of DPIs depends on several physiological (patient-dependent) and technological (device-dependent) factors. The inspiratory airflow rate is the only active force generated and operating in the system for inducing the required pressure drop and eliciting the resistance-induced turbulence needed to disaggregate the powder through the device. The present study aimed to investigate in the most prevalent respiratory disorders whether and at what extent the inspiratory airflow rate achievable when inhaling through a DPIs’ simulator reproducing different intrinsic resistance regimens (low, mid, and high resistance) is affected by peculiar changes in lung function and/or can be predicted by any specific lung function parameter.

Methods

The inspiratory airflow rate was assessed in randomized order by the In-Check DIAL G16 at low, mid, and high resistance regimens in a sample of consecutive subjects at recruitment. Independent predictors of the probability to achieve the expected inhalation airflow rate were investigated by means of a multivariate logistic regression model, specific to the disease.

Results

A total of 114 subjects were recruited (asthmatics n=30; COPD n=50, restrictive patients n=16, and normal subjects n=18). The mean values of the expected inspiratory airflow rate achieved proved significantly different within the groups (p<0.0001), independently of sex and age. In asthmatics and in COPD patients, the mid-resistance regimen proved highly associated with the highest mean values of airflow rates obtained. Low- and high-resistance regimens were significantly less likely to consent to achieve the expected level of inspiratory airflow rate (OR<1 in all comparisons). Restrictive patients performed the lowest airflow rates at the low-resistance regimen (p<0.01). Unlike FEV¹, RV in asthmatics (OR=1.008); RV and I_Raw in COPD (OR=0.587 and OR=0.901, respectively), and FIF and TLC in restrictive patients (OR=1.041, and OR=0.962, respectively) proved the only sensitive predictors of the inspiratory airflow rate achievable at the different resistive regimens.

Conclusions

The intrinsic resistive regimen of DPIs can play a critical role. The patients’ lung function profile also affects the extent of their inhalation airflow rate. Some specific lung function parameters (such as: FIF; RV; I_Raw; TLC, but not FEV₁) may be regarded as specific predictors in real-life. In order to optimize the DPI choice, further to the device’s technology, also the current patients’ lung function should be properly investigated and carefully assessed.

High-Efficiency Dry Powder Aerosol Delivery to Children: Review and Application of New Technologies

While dry powder aerosol formulations offer a number of advantages, their use in children is often limited due to poor lung delivery efficiency and difficulties with consistent dry powder inhaler (DPI) usage. Both of these challenges can be attributed to the typical use of adult devices in pediatric subjects and a lack of pediatric-specific DPI development. In contrast, a number of technologies have recently been developed or progressed that can substantially improve the efficiency and reproducibility of DPI use in children including: (i) nose-to-lung administration with small particles, (ii) active positive-pressure devices, (iii) structures to reduce turbulence and jet momentum, and (iv) highly dispersible excipient enhanced growth particle formulations. In this study, these technologies and their recent development are first reviewed in depth. A case study is then considered in which these technologies are simultaneously applied in order to enable the nose-to-lung administration of dry powder aerosol to children with cystic fibrosis (CF). Using a combination of computational fluid dynamics (CFD) analysis and realistic in vitro experiments, device performance, aerosol size increases and lung delivery efficiency are considered for pediatric-CF subjects in the age ranges of 2-3, 5-6 and 9-10 years old. Results indicate that a new 3D rod array structure significantly improves performance of a nasal cannula reducing interface loss by a factor of 1.5-fold and produces a device emitted mass median aerodynamic diameter (MMAD) of 1.67 μm. For all ages considered, approximately 70% of the loaded dose reaches the lower lung beyond the lobar bronchi. Moreover, significant and rapid size increase of the aerosol is observed beyond the larynx and illustrates the potential for targeting lower airway deposition. In conclusion, concurrent CFD and realistic in vitro analysis indicates that a combination of multiple new technologies can be implemented to overcome obstacles that currently limit the use of DPIs in children as young as two years of age.

Advancement of a Positive-Pressure Dry Powder Inhaler for Children: Use of a Vertical Aerosolization Chamber and Three-Dimensional Rod Array Interface

PURPOSE

Available dry powder inhalers (DPIs) have very poor lung delivery efficiencies in children. The objective of this study was to advance and experimentally test a positive-pressure air-jet DPI for children based on the use of a vertical aerosolization chamber and new patient interfaces that contain a three-dimensional (3D) rod array structure.

METHODS

Aerosolization performance of different air-jet DPI designs was first evaluated based on a 10 mg powder fill mass of a spray-dried excipient enhanced growth (EEG) formulation. Devices were actuated with positive pressure using flow rate (10-20 L/min) and inhaled volume (750 ml) conditions consistent with a 5-year-old child. Devices with best performance were connected to different mouthpiece designs to determine the effect on aerosolization and tested for aerosol penetration through a realistic pediatric in vitro mouth-throat model.

RESULTS

Use of the new vertical aerosolization chamber resulted in high quality aerosol formation. Inclusion of a 3D rod array structure in the mouthpiece further reduced aerosol size by approximately 20% compared to conditions without a rod array, and effectively dissipated the turbulent jet leaving the device. Best case device and mouthpiece combinations produced < 2% mouth-throat depositional loss and > 70% lung delivery efficiency based on loaded dose.

CONCLUSIONS

In conclusion, use of a 3D rod array in the MP of a positive-pressure air-jet DPI was found to reduce aerosol size by 20%, not significantly increase MP depositional loss, reduce mouth-throat deposition by 6.4-fold and enable lung delivery efficiency as high as 73.4% of loaded dose based on pediatric test conditions.

Development of Dry Powder Inhaler Patient Interfaces for Improved Aerosol Delivery to Children

The objective of this study was to explore different internal flow passages in the patient interface region of a new air-jet-based dry powder inhaler (DPI) in order to minimize device and extrathoracic aerosol depositional losses using computational fluid dynamics (CFD) simulations. The best-performing flow passages were used for oral and nose-to-lung (N2L) aerosol delivery in pediatric extrathoracic airway geometries consistent with a 5-year-old child. Aerosol delivery conditions were based on a previously developed and tested air-jet DPI device and included a base flow rate of 13.3 LPM (delivered from a small ventilation bag) and an inhaled air volume of 750 mL. Initial CFD models of the system clearly established that deposition on either the back of the throat or nasal cannula bifurcation was strongly correlated with the maximum velocity exiting the flow passage. Of all designs tested, the combination of a 3D rod array and rapid expansion of the flow passage side walls was found to dramatically reduce interface and device deposition and improve lung delivery of the aerosol. For oral aerosol administration, the optimal flow passage compared with a base case reduced device, mouthpiece, and mouth-throat deposition efficiencies by factors of 8-, 3-, and 2-fold, respectively. For N2L aerosol administration, the optimal flow pathway compared with a base case reduced device, nasal cannula, and nose-throat deposition by 16-, 6-, and 1.3-fold, respectively. In conclusion, a new patient interface design including a 3D rod array and rapid expansion dramatically improved transmission efficiency of a dry powder aerosol.

Development of an Inline Dry Powder Inhaler for Oral or Trans-Nasal Aerosol Administration to Children

Background: Dry powder inhalers (DPIs) offer a number of advantages, such as rapid delivery of high-dose inhaled medications; however, DPI use in children is often avoided due to low lung delivery efficiency and difficulty in operating the device. The objective of this study was to develop a high-efficiency inline DPI for administering aerosol therapy to children with the option of using either an oral or trans-nasal approach. Methods: An inline DPI was developed that consisted of hollow inlet and outlet capillaries, a powder chamber, and a nasal or oral interface. A ventilation bag or compressed air was used to actuate the device and simultaneously provide a full deep inspiration consistent with a 5-year-old child. The powder chamber was partially filled with a model spray-dried excipient enhanced growth powder formulation with a mass of 10 mg. Device aerosolization was characterized with cascade impaction, and aerosol transmissions through oral and nasal in vitro models were assessed. Results: Best device performance was achieved when all actuation air passed through the powder chamber (no bypass flow) resulting in an aerosol mean mass median aerodynamic diameter (MMAD) <1.75 μm and a fine particle fraction (<5 μm) ≥90% based on emitted dose. Actuation with the ventilation bag enabled lung delivery efficiency through the nasal and oral interfaces to a tracheal filter of 60% or greater, based on loaded dose. In both oral and nose-to-lung (N2L) administrations, extrathoracic depositional losses were <10%. Conclusion: In conclusion, this study has proposed and initially developed an efficient inline DPI for delivering spray-dried formulations to children using positive pressure operation. Actuation of the device with positive pressure enabled effective N2L aerosol administration with a DPI, which may be beneficial for subjects who are too young to use a mouthpiece or to simultaneously treat the nasal and lung airways of older children.

Single Inhaler LABA/LAMA for COPD

Chronic obstructive pulmonary disease (COPD) is a common disabling disease characterized by progressive airflow obstruction. Great efforts were spent in the development of drugs able to improve symptoms, quality of life, reduce exacerbations, hospitalizations and the frequency of death of patients with COPD. The cornerstones of treatment are bronchodilator drugs of two different classes: beta agonists and muscarinic antagonists. Currently the Global initiative for COPD suggests the use of long acting beta agonists (LABAs) and long acting muscarinic antagonists (LAMAs) in combination for the majority of COPD patients, thus great interest is associated with the developing of LAMA/LABA fixed combination in the maintenance treatment of stable COPD. Many LAMA/LABA fixed dose combinations have been licensed in different countries and the clinical use of these drugs stimulated the performance of many clinical trials. The purpose of this review is a complete criticism of pharmacological and clinical aspects related to the use of LAMA/LABA single inhalers for the maintenance treatment of stable COPD, with particular mention to the most debated topics and future prospects in the field.

Targeting inhaled aerosol delivery to upper airways in children: Insight from computational fluid dynamics (CFD)

Despite the prevalence of inhalation therapy in the treatment of pediatric respiratory disorders, most prominently asthma, the fraction of inhaled drugs reaching the lungs for maximal efficacy remains adversely low. By and large drug delivery devices and their inhalation guidelines are typically derived from adult studies with child dosages adapted according to body weight. While it has long been recognized that physiological (e.g. airway sizes, breathing maneuvers) and physical transport (e.g. aerosol dynamics) characteristics are critical in governing deposition outcomes, such knowledge has yet to be extensively adapted to younger populations. Motivated by such shortcomings, the present work leverages in a first step in silico computational fluid dynamics (CFD) to explore opportunities for augmenting aerosol deposition in children based on respiratory physiological and physical transport determinants. Using an idealized, anatomically-faithful upper airway geometry, airflow and aerosol motion are simulated as a function of age, spanning a five year old to an adult. Breathing conditions mimic realistic age-specific inhalation maneuvers representative of Dry Powder Inhalers (DPI) and nebulizer inhalation. Our findings point to the existence of a single dimensionless curve governing deposition in the conductive airways via the dimensionless Stokes number (Stk). Most significantly, we uncover the existence of a distinct deposition peak irrespective of age. For the DPI simulations, this peak (∼ 80%) occurs at Stk ≈ 0.06 whereas for nebulizer simulations, the corresponding peak (∼ 45%) occurs in the range of Stk between 0.03-0.04. Such dimensionless findings hence translate to an optimal window of micron-sized aerosols that evolves with age and varies with inhalation device. The existence of such deposition optima advocates revisiting design guidelines for optimizing deposition outcomes in pediatric inhalation therapy.

Assessment of the Power Required for Optimal Use of Current Inhalation Devices

Background: Inhalation of medications is the cornerstone in the treatment of patients with lung diseases. A variety of inhalation devices exists and each device has specific requirements to achieve optimum inhalation of the drug. The goal of this study was to establish a clear overview on performance requirements of standard inhalation devices that should be met by the patient's breathing power and to develop a new method to measure the individual performance data. Materials and Methods: An optimum and still acceptable required breathing power (P in watts) was calculated for each device with the aid of individual device flow rates (determined by a literature search) and the flow resistances (by measuring the pressure drop over the different inhalation devices). For the in vivo part of the study, peak inspiratory flow and peak inspiratory pressure drop were measured in 21 adult patients with asthma or chronic obstructive pulmonary disease and healthy volunteers and the peak inspiratory power (PIPO in watts) was calculated. Results: Nearly no power is needed to achieve optimum results when using pressurized metered dose inhalers. For dry powder inhalers, the required power depends on the specific inhalation device. Conclusions: Inhalation devices impose differing demands on the inspiratory breathing power of patients. To ensure adequate use of the different devices, a cheap and simple assessment of patients' PIPO may be one option.

Maintenance inhaler preference, attribute importance, and satisfaction in prescribing physicians and patients with asthma, COPD, or asthma-COPD overlap syndrome consulting for routine care

Background

In respiratory disorders, patient- and physician-perceived satisfaction with the maintenance inhaler device is an important factor driving treatment compliance and outcomes. We examine inhaler preferences in asthma and COPD from patient and physician perspectives, particularly focusing on the relative importance of individual device attributes and patient characteristics guiding inhaler choice.

Materials and methods

Real-world data from >7,300 patients with asthma, COPD, or asthma–COPD overlap syndrome (ACOS) consulting for routine care were derived from respiratory Disease Specific Programs conducted in Europe, USA, Japan, and China. Outcome variables included current pattern of inhaled maintenance therapy and device type, physician preference, patient-reported device attribute importance, and satisfaction.

Results

The most commonly prescribed inhalers for maintenance therapy of asthma, COPD, and ACOS were dry powder inhalers (62.8%–88.5% of patients) and pressurized metered dose inhalers (18.9%–35.3% of patients). One-third of physicians stated no preference for maintenance device when prescribing treatment, and less than one-third of patients reported being “extremely satisfied” with any attribute of their device. Instructions being “simple and easy to follow” was the inhaler attribute most commonly selected as important. For approximately one-third of patients across all groups, “ease of use/suitability of inhaler device” was a reason for the prescribing decision, as stated by the physician. Device characteristics were more likely to impact the prescribing decision in older patients (in asthma and COPD; P<0.01) and those with worse disease severity (in COPD; P<0.001).

Conclusion

A relatively high proportion of physicians had no preference for inhaler type across asthma, COPD, and ACOS. Simplicity of use was the most important inhaler attribute from a patient’s perspective. Physicians appeared to place most importance on ease of use and device suitability when selecting inhalers for older patients and those with more severe disease, particularly in COPD.

Guiding Inspiratory Flow: Development of the In-Check DIAL G16, a Tool for Improving Inhaler Technique

Portable inhalers are divisible into those that deliver medication by patient triggering (pMDIs: a gentle slow inhalation) and those that use the patient's inspiratory effort as the force for deaggregation and delivery (DPIs: a stronger deeper inspiratory effort). Patient confusion and poor technique are commonplace. The use of training tools has become standard practice, and unique amongst these is an inspiratory flow meter (In-Check) which is able to simulate the resistance characteristics of different inhalers and, thereby, guide the patient to the correct effort. In-Check's origins lie in the 1960s peak expiratory flow meters, the development of the Mini-Wright peak flow meter, and inspiratory flow assessment via the nose during the 1970s–1980s. The current device (In-Check DIAL G16) is the third iteration of the original 1998 training tool, with detailed and ongoing assessments of all common inhaler resistances (including combination and breath-actuated inhaler types) summarised into resistance ranges that are preset within the device. The device works by interpolating one of six ranges with the inspiratory effort. Use of the tool has been shown to be contributory to significant improvements in asthma care and control, and it is being advocated for assessment and training in irreversible lung disease.

Drug Delivery Devices for Inhaled Medicines

Historically, the inhaled route has been used for the delivery of locally-acting drugs for the treatment of respiratory conditions, such as asthma, COPD, and airway infections. Targeted delivery of substances to the lungs has some key advantages over systemic administration, including a more rapid onset of action, an increased therapeutic effect, and, depending on the agent inhaled, reduced systemic side effects since the required local concentration in the lungs can be obtained with a lower dose. Fortunately, when designed properly, inhaled drug delivery devices can be very effective and safe for getting active agents directly to their site of action.

Prerequisites for a dry powder inhaler for children with cystic fibrosis

Correct inhalation technique is essential for effective use of dry powder inhalers (DPIs), as their effectiveness largely depends on the patient's inhalation manoeuvre. Children are an especially challenging target population for DPI development due to the large variability in understanding and inspiratory capacities. We previously performed a study in which we determined the prerequisites for a paediatric DPI in a mostly healthy paediatric population, for which we used an empty test inhaler with variable internal airflow resistance and mouthpiece. In the current study we investigated what specifications are required for a DPI for children with cystic fibrosis (CF), for which we expanded on our previous findings. We recorded flow profiles of 35 children with CF (aged 4.7-14.7 years) at three airflow resistances (0.031-0.045 kPa0.5.min.L-1) from which various inspiratory parameters were computed. Obstructions in the mouth during inhalation were recorded with a sinuscope. All children were able to perform a correct inhalation manoeuvre, although video analysis showed that children did not place the inhaler correctly in the mouth in 17% of the cases. No effect was found of medium to high airflow resistance on total inhaled volume, which implies that the whole resistance range tested is suitable for children with CF aged 4-14 years. No effect could be established of either mouthpiece design or airflow resistance on the occurrence of obstructions in the mouth cavity. This study confirms our previous conclusion that the development of DPIs specifically for children is highly desired. Such a paediatric DPI should function well at 0.5 L inhaled volume and a peak inspiratory flow rate of 20 to 30 L/min, depending on the internal airflow resistance. This resistance can be increased up to 0.045 kPa0.5.min.L-1 (medium-high) to reduce oropharyngeal deposition. A higher resistance may be less favourable due to its compromising effect on PIF and thereby on the energy available for powder dispersion.

Influences of gender and anthropometric features on inspiratory inhaler acoustics and peak inspiratory flow rate

Inhalers are hand-held devices used to treat chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). Medication is delivered from an inhaler to the user through an inhalation maneuver. It is unclear whether gender and anthropometric features such as age, height, weight and body mass index (BMI) influence the acoustic properties of inspiratory inhaler sounds and peak inspiratory flow rate (PIFR) in inhalers. In this study, healthy male (n=9) and female (n=7) participants were asked to inhale at an inspiratory flow rate (IFR) of 60 L/min in four commonly used inhalers (Turbuhaler(™), Diskus(™), Ellipta(™) and Evohaler(™)). Ambient inspiratory sounds were recorded from the mouthpiece of each inhaler and over the trachea of each participant. Each participant's PIFR was also recorded for each of the four inhalers. Results showed that gender and anthropometric features have the potential to influence the spectral properties of ambient and tracheal inspiratory inhaler sounds. It was also observed that males achieved statistically significantly higher PIFRs in each inhaler in comparison to females (p<;0.05). Acoustic features were found to be significantly different across inhalers suggesting that acoustic features are modulated by the inhaler design and its internal resistance to airflow.

Dry powder inhalation: past, present and future

INTRODUCTION

Early dry powder inhalers (DPIs) were designed for low drug doses in asthma and COPD therapy. Nearly all concepts contained carrier-based formulations and lacked efficient dispersion principles. Therefore, particle engineering and powder processing are increasingly applied to achieve acceptable lung deposition with these poorly designed inhalers. Areas covered: The consequences of the choices made for early DPI development with respect of efficacy, production costs and safety and the tremendous amount of energy put into understanding and controlling the dispersion performance of adhesive mixtures are discussed. Also newly developed particle manufacturing and powder formulation processes are presented as well as the challenges, objectives, and new tools available for future DPI design. Expert opinion: Improved inhaler design is desired to make DPIs for future applications cost-effective and safe. With an increasing interest in high dose drug delivery, vaccination and systemic delivery via the lungs, innovative formulation technologies alone may not be sufficient. Safety is served by increasing patient adherence to the therapy, minimizing the use of unnecessary excipients and designing simple and self-intuitive inhalers, which give good feedback to the patient about the inhalation maneuver. For some applications, like vaccination and delivery of hygroscopic formulations, disposable inhalers may be preferred.

Inhalation device requirements for patients' inhalation maneuvers

BACKGROUND

Inhaled drugs are the mainstay of treatment for lung diseases such as asthma and chronic obstructive pulmonary disease. However, failure to use inhalation devices correctly can lead to a poorly controlled status. A vast number of inhalation devices exist and each device has specific requirements to achieve optimum inhalation of the drug. Currently, there is no overview of inhalation requirements considering all devices. This article presents a review of the literature on different inhalation device requirements and incorporates the data into a new inhalation flow algorithm.

METHODS

Data from literature on commercially available inhalation devices were evaluated and parameters, such as inhalation flow rate, flow acceleration, inhalation volume, and inspiration time assessed for the required inhalation maneuver specific to the device. All agreed upon data points were used to develop an inhalation flow algorithm.

RESULTS

The literature analysis revealed availability of robust data for the required inhalation flow characteristics for most devices and thus for the development of an algorithm. For those devices for which these parameters are not published, the minimum required flow criteria were defined based on published data regarding individual aspects of aerosol quality.

CONCLUSIONS

This review provides an overview of inhalation devices available on the market regarding requirements for an acceptable inhalation maneuver and shows which goals should be achieved in terms of inhalation flows. The presented algorithm can be used to develop a new computer based measurement system which could help to test and train patients' individual inhalation maneuvers with their inhalation devices.