Effect of Facial Material Softness and Applied Force on Face Mask Dead Volume, Face Mask Seal, and Inhaled Corticosteroid Delivery Through an Idealized Infant Replica

Use of Airway Replicas in Lung Delivery Applications

The use of extrathoracic airway replicas in optimization of drug delivery to the lungs with nebulizers, dry powder inhalers (DPIs) and pressurized metered-dose inhalers (pMDIs) is discussed. Such airway replicas have been useful in evaluating new pulmonary drug delivery platforms mainly based on the comparison of the total lung dose (TLD) and the aerodynamic particle size distribution (APSD) of the aerosol distal to the physical models. The ability of these in vitro methods to replicate in vivo results has allowed advancements in respiratory drug delivery and in the accuracy and utility of in vitro-in vivo correlations (IVIVCs).

In vitro - in vivo correlation of intranasal drug deposition

In vitro - in vivo correlation (IVIVC) allows prediction of in vivo drug deposition from a nasally inhaled drug based on in vitro drug measurements. In vitro measurements include physical particle characterization and, more recently, deposition studies using anatomical models. Currently, there is a lack of IVIVC for deposition measurements in anatomical models, especially for deposition patterns in various nasal cavity regions. Therefore, improvement of in vitro and in vivo measurement methods and knowledge about nasal deposition mechanisms should help IVIVC in the future.

Innovative preclinical models for pulmonary drug delivery research

Introduction: Pulmonary drug delivery is a complex field of research combining physics which drive aerosol transport and deposition and biology which underpins efficacy and toxicity of inhaled drugs. A myriad of preclinical methods, ranging from in-silico to in-vitro, ex-vivo and in-vivo, can be implemented.Areas covered: The present review covers in-silico mathematical and computational fluid dynamics modelization of aerosol deposition, cascade impactor technology to estimated drug delivery and deposition, advanced in-vitro cell culture methods and associated aerosol exposure, lung-on-chip technology, ex-vivo modeling, in-vivo inhaled drug delivery, lung imaging, and longitudinal pharmacokinetic analysis.Expert opinion: No single preclinical model can be advocated; all methods are fundamentally complementary and should be implemented based on benefits and drawbacks to answer specific scientific questions. The overall best scientific strategy depends, among others, on the product under investigations, inhalation device design, disease of interest, clinical patient population, previous knowledge. Preclinical testing is not to be separated from clinical evaluation, as small proof-of-concept clinical studies or conversely large-scale clinical big data may inform preclinical testing. The extend of expertise required for such translational research is unlikely to be found in one single laboratory calling for the setup of multinational large-scale research consortiums.

Development and Evaluation of a Family of Human Face and Upper Airway Models for the Laboratory Testing of Orally Inhaled Products

Many orally inhaled products are supplied with a facemask instead of a mouthpiece, enabling aerosolized medication to be transferred from the inhaler to the lungs when the user lacks the capability to use a mouthpiece. Until recently, laboratory evaluation of an orally inhaled product-facemask was frequently undertaken by removing the facemask, treating the facemask adapter as being equivalent to a mouthpiece. Measurements of delivered drug mass were therefore subject to bias arising from the absence of dead volume, had the facemask been present. We have described the development of the Aerosol Delivery to an Anatomic Model (ADAM) infant, small child, and adult faces and upper airways, and their subsequent evaluation. Each model possesses physical features of appropriate size, and the soft tissues are also simulated. Rudimentary underlying bony structure is also present, because its purpose is only to provide support, enabling the mechanical response of the facial soft tissues when a facemask is applied to be realized. A realistic upper airway (nasopharynx for the infant model, naso- and oropharynx for the child and oropharynx for the adult models) is also incorporated, so that each model can be used to determine the mass of inhaled medication likely to penetrate as far as the lungs where therapy is intended to be applied. Measurements of the mass of pressurized metered-dose inhaler-delivered salbutamol at a filter distal to the upper airway of each model, simulating age-appropriate tidal breathing, were remarkably consistent, almost all being in the range 0.3 to 1.0 μg/kg across the model age ranges, when expressed as a fraction of body weight.

Powder aerosol delivery through nasal high-flow system: In vitro feasibility and influence of process conditions

We aimed to obtain fundamental information for potential pulmonary delivery of powder aerosols using a clinically-approved nasal high-flow system (AIRVO), with spray-dried mannitol (SD-Man) being a model powder. Compressed air exiting the AIRVO at set 'dispersion' air flow rates dispersed SD-Man loaded in an Osmohaler^® into a human nasal airway replica (NAR) coupled downstream to a Next Generation Impactor (NGI) running at specific 'inspiratory' flow rates. Increasing the dispersion flow rate from 30 to 60L/min increased powder deposition in the NAR from 50 to 70% of the emitted dose, while decreased the NGI deposition from 50 to 30% of the emitted dose. The inspiratory flow rate did not affect powder deposition in the NAR and NGI. In contrast, as the inspiratory flow rate was increased from 15 to 40L/min, powder recovery, emitted fraction, and fine particle fraction below 5μm (as aerosol performance indices) were increased from 90, 30 and 5% to 97, 45 and 8% of the loaded dose, respectively. The dispersion flow rate did not change the performance indices. Importantly, heating and humidification of dispersion airflow, loaded doses, and nasal cannula sizes did not greatly affect the aerosol characteristics.

Clinically Relevant In Vitro Testing of Orally Inhaled Products-Bridging the Gap Between the Lab and the Patient

Current pharmacopeial methods for in vitro orally inhaled product (OIP) performance testing were developed primarily to support requirements for drug product registration and quality control. In addition, separate clinical studies are undertaken in order to quantify safety and efficacy in the hands of the patient. However, both laboratory and clinical studies are time-consuming and expensive and generally do not investigate either the effects of misuse or the severity of the respiratory disease being treated. The following modifications to laboratory evaluation methodologies can be incorporated without difficulty to provide a better linkage from in vitro testing to clinical reality: (1) examine all types of OIP with patient-representative breathing profiles which represent normal inhaler operation in accordance with the instructions for use (IFU); (2) evaluate OIP misuse, prioritizing the importance of such testing on the basis of (a) probability of occurrence and (b) consequential impact in terms of drug delivery in accordance with the label claim; and (3) use age-appropriate patient-simulated face and upper airway models for the evaluation of OIPs with a facemask. Although it is not necessarily foreseen that these suggestions would form part of future routine quality control testing of inhalers, they should provide a closer approximation to the clinical setting and therefore be useful in the preparation for in vivo studies and in improving guidance for correct use.

More Realistic Face Model Surface Improves Relevance of Pediatric In-Vitro Aerosol Studies

BACKGROUND

Various hard face models are commonly used to evaluate the efficiency of aerosol face masks. Softer more realistic "face" surface materials, like skin, deform upon mask application and should provide more relevant in-vitro tests. Studies that simultaneously take into consideration many of the factors characteristic of the in vivo face are lacking. These include airways, various application forces, comparison of various devices, comparison with a hard-surface model and use of a more representative model face based on large numbers of actual faces.

AIM

To compare mask to "face" seal and aerosol delivery of two pediatric masks using a soft vs. a hard, appropriately representative, pediatric face model under various applied forces.

METHODS

Two identical face models and upper airways replicas were constructed, the only difference being the suppleness and compressibility of the surface layer of the "face." Integrity of the seal and aerosol delivery of two different masks [AeroChamber (AC) and SootherMask (SM)] were compared using a breath simulator, filter collection and realistic applied forces.

RESULTS

The soft "face" significantly increased the delivery efficiency and the sealing characteristics of both masks. Aerosol delivery with the soft "face" was significantly greater for the SM compared to the AC (p< 0.01). No statistically significant difference between the two masks was observed with the hard "face."

CONCLUSIONS

The material and pliability of the model "face" surface has a significant influence on both the seal and delivery efficiency of face masks. This finding should be taken into account during in-vitro aerosol studies.

An Apparatus to Deliver Mannitol Powder for Bronchial Provocation in Children Under Six Years Old

BACKGROUND

Currently bronchial provocation testing (BPT) using mannitol powder cannot be performed in children under 6 years. A primary reason is it is challenging for children at this age to generate a consistent inspiratory effort to inhale mannitol efficiently from a dry powder inhaler. A prototype system, which does not require any inhalation training from the pediatric subject, is reported here. It uses an external source of compressed air to disperse mannitol powder into a commercial holding chamber. Then the subject uses tidal breathing to inhale the aerosol.

METHOD

The setup consists of a commercially available powder disperser and Volumatic™ holding chamber. Taguchi experimental design was used to identify the effect of dispersion parameters (flow rate of compressed air, time compressed air is applied, mass of powder, and the time between dispersion and inhalation) on the fine particle dose (FPD). The prototype was tested in vitro using a USP throat connected to a next generation impactor. The aerosols from the holding chamber were drawn at 10 L/min. A scaling factor for estimating the provoking dose to induce a 15% reduction in forced expiratory volume in 1 second (FEV1) (PD15) was calculated using anatomical dimensions of the human respiratory tract at various ages combined with known dosing values from the adult BPT.

RESULTS

Consistent and doubling FPDs were successfully generated based on the Taguchi experimental design. The FPD was reliable over a range of 0.8 (±0.09) mg to 14 (±0.94) mg. The calculated PD15 for children aged 1-6 years ranged from 7.1-30 mg. The FPDs generated from the proposed set up are lower than the calculated PD15 and therefore are not expected to cause sudden bronchoconstriction.

CONCLUSION

A prototype aerosol delivery system has been developed that is consistently able to deliver doubling doses suitable for bronchial provocation testing in young children.