Aerosol therapy in children: challenges and solutions

Dos and don'ts to optimize transnasal aerosol drug delivery in clinical practice

INTRODUCTION

Transnasal aerosol drug delivery has become widely accepted for treating acutely ill infants, children, and adults. More recently aerosol administration to wider populations receiving high and low-flow nasal oxygen has become common practice.

AREAS COVERED

Skepticism of insufficient aerosol delivery to the lungs has been tempered by multiple in vitro explorations of variables to optimize delivery efficiency. Additionally, clinical studies demonstrated comparable clinical responses to orally inhaled aerosols. This paper provides essential clinical guidance on how to improve transnasal aerosol delivery based on device-, settings-, and drug-related optimization to serve as a resource for educational initiatives and quality enhancement endeavors at healthcare institutions.

EXPERT OPINION

Transnasal aerosol delivery is proliferating worldwide, but indiscriminate use of excessive-high flows, poor selection and placement of aerosol devices and circuits can greatly reduce aerosol delivery and efficacy, potentially compromising treatment to acute and critically ill patients. Attention to these details can improve inhaled dose by an order of magnitude, making the difference between effective treatment and the progression to more invasive ventilatory support, with greater inherent risk and cost. These revelations have prompted specific recommendations for optimal delivery, driving advancements in aerosol generators, formulations, and future device designs to administer aerosols and maximize treatment effectiveness.

Individualized aerosol medicine: Integrating device into the patient

Pulmonary drug delivery is complex due to several challenges including disease-, patient-, and clinicians-related factors. Although many inhaled medications are available in aerosol medicine, delivering aerosolized medications to patients requires effective disease management. There is a large gap in the knowledge of clinicians who select and provide instructions for the correct use of aerosol devices. Since improper device selection, incorrect inhaler technique, and poor patient adherence to prescribed medications may result in inadequate disease control, individualized aerosol medicine is essential for effective disease management and control. The components of individualized aerosol medicine include: (1) Selecting the right device, (2) Selecting the right interface, (3) Educating the patient effectively, and (4) Increasing patient adherence to therapy. This paper reviews each of these components and provides recommendations to integrate the device and interface into the patient for better clinical outcomes.

Fluid-structure interaction analysis of airflow, structural mechanics and aerosol dynamics in a four-generation acinar model

Elucidating the aerosol dynamics in the pulmonary acinar region is imperative for both health risk assessment and inhalation therapy, especially nowadays with the occurrence of the global COVID-19 pandemic. During respiration, the chest's outward elastic recoil and the lungs' inward elastic recoil lead to a change of transmural pressure, which drives the lungs to expand and contract to inhale and expel airflow and aerosol. In contrast to research using predefined wall motion, we developed a four-generation acinar model and applied an oscillatory pressure on the model outface to generate structure deformation and airflow. With such tools at hand, we performed a computational simulation that addressed both the airflow characteristic, structural mechanics, and aerosol dynamics in the human pulmonary acinar region. Our results showed that there is no recirculating flow in the sac. The structural displacement and stress were found to be positively related to the change of model volume and peaked at the end of inspiration. It was noteworthy that the stress distribution on the acinar wall was significantly heterogeneous, and obvious concentrations of stress were found at the junction of the alveoli and the ducts or the junction of the alveoli and alveoli in the sac. Our result demonstrated the effect of breathing cycles and aerosol diameter on deposition fraction and location of aerosols in the size range of 0.1-5 μm. Multiple respiratory cycles were found necessary for adequate deposition or escape of submicron particles while having a negligible influence on the transport of large particles, which were dominated by gravity. Our study can provide new insights into the further investigation of airflow, structural mechanics, and aerosol dynamics in the acinar depth.

Evaluating dry powder inhalers: From in vitro studies to mobile health technologies

Dry powder inhalers (DPIs) are essential in treating patients with pulmonary diseases. Since DPIs were introduced in the 1960s, a remarkable improvement has been made in their technology, dose delivery, efficiency, reproducibility, stability, and performance based on safety and efficacy. While there are many DPIs on the market and several more under development, it is vital to evaluate the performance of DPIs for effective aerosol drug delivery to patients with respiratory disorders. Their performance evaluation includes particle size, metering system, device design, dose preparation, inhalation technique, and patient-device integration. The purpose of this paper is to review current literature evaluating DPIs through in vitro studies, computational fluid models, and in vivo/clinical studies. We will also explain how mobile health applications are used to monitor and evaluate patients' adherence to prescribed medications.

Treating COPD Patients with Inhaled Medications in the Era of COVID-19 and Beyond: Options and Rationales for Patients at Home

COVID-19 has affected millions of patients, caregivers, and clinicians around the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads via droplets and close contact from person to person, and there has been an increased concern regarding aerosol drug delivery due to the potential aerosolizing of viral particles. To date, little focus has been given to aerosol drug delivery to patients with COVID-19 treated at home to minimize their hospital utilization. Since most hospitals were stressed with multiple admissions and experienced restricted healthcare resources in the era of COVID-19 pandemic, treating patients with COPD at home became essential to minimize their hospital utilization. However, guidance on how to deliver aerosolized medications safely and effectively to this patient population treated at home is still lacking. In this paper, we provide some strategies and rationales for device and interface selection, delivery technique, and infection control for patients with COPD who are being treated at home in the era of COVID-19 and beyond.

Advanced human-relevant in vitro pulmonary platforms for respiratory therapeutics

Over the past years, advanced in vitro pulmonary platforms have witnessed exciting developments that are pushing beyond traditional preclinical cell culture methods. Here, we discuss ongoing efforts in bridging the gap between in vivo and in vitro interfaces and identify some of the bioengineering challenges that lie ahead in delivering new generations of human-relevant in vitro pulmonary platforms. Notably, in vitro strategies using foremost lung-on-chips and biocompatible "soft" membranes have focused on platforms that emphasize phenotypical endpoints recapitulating key physiological and cellular functions. We review some of the most recent in vitro studies underlining seminal therapeutic screens and translational applications and open our discussion to promising avenues of pulmonary therapeutic exploration focusing on liposomes. Undeniably, there still remains a recognized trade-off between the physiological and biological complexity of these in vitro lung models and their ability to deliver assays with throughput capabilities. The upcoming years are thus anticipated to see further developments in broadening the applicability of such in vitro systems and accelerating therapeutic exploration for drug discovery and translational medicine in treating respiratory disorders.

Cellular Therapy for the Treatment of Paediatric Respiratory Disease

Respiratory disease is the leading cause of death in children under the age of 5 years old. Currently available treatments for paediatric respiratory diseases including bronchopulmonary dysplasia, asthma, cystic fibrosis and interstitial lung disease may ameliorate symptoms but do not offer a cure. Cellular therapy may offer a potential cure for these diseases, preventing disease progression into adulthood. Induced pluripotent stem cells, mesenchymal stromal cells and their secretome have shown great potential in preclinical models of lung disease, targeting the major pathological features of the disease. Current research and clinical trials are focused on the adult population. For cellular therapies to progress from preclinical studies to use in the clinic, optimal cell type dosage and delivery methods need to be established and confirmed. Direct delivery of these therapies to the lung as aerosols would allow for lower doses with a higher target efficiency whilst avoiding potential effect of systemic delivery. There is a clear need for research to progress into the clinic for the treatment of paediatric respiratory disease. Whilst research in the adult population forms a basis for the paediatric population, varying disease pathology and anatomical differences in paediatric patients means a paediatric-centric approach must be taken.

Quantifying Delivered Dose with Jet and Mesh Nebulizers during Spontaneous Breathing, Noninvasive Ventilation, and Mechanical Ventilation in a Simulated Pediatric Lung Model with Exhaled Humidity

Acutely ill children may transition between spontaneous breathing (SB), noninvasive ventilation (NIV), and mechanical ventilation (MV), and commonly receive the same drug dosage with each type of ventilatory support and interface. This study aims to determine the aerosol deposition with jet (JN) and mesh nebulizers (MN) during SB, NIV, and MV using a pediatric lung model. Drug delivery with JN (Mistymax10) and MN (Aerogen Solo) was compared during SB, NIV, and MV using three different lung models set to simulate the same breathing parameters (Vt 250 mL, RR 20 bpm, I:E ratio 1:3). A heated humidifier was placed between the filter and test lung to simulate exhaled humidity (35 ± 2 °C, 100% RH) with all lung models. Albuterol sulfate (2.5 mg/3 mL) was delivered, and the drug deposited on an absolute filter was eluted and analyzed with spectrophotometry. Aerosol delivery with JN was not significantly different during MV, NIV, and SB (p = 0.075), while inhaled dose obtained with MN during MV was greater than NIV and SB (p = 0.001). The delivery efficiency of MN was up to 3-fold more than JN during MV (p = 0.008), NIV (p = 0.005), and SB (p = 0.009). Delivered dose with JN was similar during MV, NIV, and SB, although the delivery efficiency of MN differs with different modes of ventilation.

A whole lung in silico model to estimate age dependent particle dosimetry

Anatomical and physiological changes alter airflow characteristics and aerosol distribution in the developing lung. Correlation between age and aerosol dosimetry is needed, specifically because youth are more susceptible to medication side effects. In this study, we estimate aerosol dosages (particle diameters of 1, 3, and 5 [Formula: see text]m) in a 3 month-old infant, a 6 year-old child, and a 36 year-old adult by performing whole lung subject-specific particle simulations throughout respiration. For 3 [Formula: see text]m diameter particles we estimate total deposition as 88, 73, and [Formula: see text] and the conducting versus respiratory deposition ratios as 4.0, 0.5, and 0.4 for the infant, child, and adult, respectively. Due to their lower tidal volumes and functional residual capacities the deposited mass is smaller while the tissue concentrations are larger in the infant and child subjects, compared to the adult. Furthermore, we find that dose cannot be predicted by simply scaling by tidal volumes. These results highlight the need for additional clinical and computational studies that investigate the efficiency of treatment, while optimizing dosage levels in order to alleviate side effects, in youth.

A path to successful patient outcomes through aerosol drug delivery to children: a narrative review

Although using aerosolized medications is a mainstay of treatment in children with asthma and other respiratory diseases, there are many issues in terms of device and interface selection, delivery technique and dosing, as well as patient and parental education that have not changed for half a century. Also, due to many aerosol devices and interfaces available on the market and the broad range of patient characteristics and requirements, providing effective aerosol therapy to children becomes a challenge. While aerosol delivery devices are equally effective, if they are age-appropriate and used correctly, the majority of aerosol devices require multiple steps to be used efficiently. Unfortunately, many children with pulmonary diseases have problems with the correct delivery technique and do not gain therapeutic benefits from therapy that result in poor disease management and increased healthcare costs. Therefore, the purpose of this paper is to review the current knowledge on aerosol delivery devices used in children and guide clinicians on the optimum device- and interface-selection, delivery technique, and dosing in this patient population. Strategies on how to deliver aerosolized medications in crying and distressed children and how to educate parents on aerosol therapy and promote patient adherence to prescribed medications are also provided. Future directions of aerosol therapy in children should focus on these issues and implement policies and clinical practices that highlight the potential solutions to these problems.

Quantifying continuous nebulization via high flow nasal cannula and large volume nebulizer in a pediatric model

BACKGROUND

Use of high flow nasal cannula (HFNC) to deliver aerosolized medications to children has gained considerable interest. However, data on continuous albuterol delivery (CAD) via HFNC are lacking. This study quantified CAD via HFNC/vibrating mesh nebulizer (VMN) and large-volume jet nebulizer (LVN) with face mask (FM) in a pediatric model. Aerosol delivery with two HFNC cannula designs were also compared.

METHODS

A pediatric manikin was connected to a lung simulator (Vt = 150 mL, RR = 28 breaths/minute, I:E 1:2.4) via collecting filter at the carina. XL Pediatric and SML Adult HFNC designs were tested to determine optimal cannula design for CAD. VMN was placed Before humidifier (37°C), albuterol (5 mg/mL) was nebulized at 3, 6, and 12 L/minute (n = 3). To compare HFNC/VMN with LVN and FM, albuterol (15 mg/hour) was aerosolized for 3 hours/device (n = 3). LVN was connected to FM and filled with 9 mL of albuterol (5 mg/mL) and 66 mL of normal saline to deliver 25 mL/hour at 13 L/minute. VMN was connected to the infusion pump to deliver 7.5 mL/hr of albuterol (2 mg/mL). Drug eluted from filters was assayed with UV spectrophotometry (276 nm).

RESULTS

Optimal aerosol delivery occurred at 3 L/minute (12.6% ± 0.5%) with SML Adult HFNC (P = .04). When used for CAD, inhaled drug delivery with HFNC/VMN (2.2 mg/hr ± 0.1, 14.8% ± 0.7%) was significantly greater than LVN and FM (0.48 ± 0.09 mg/hour, 3.2% ± 0.6%) (P = .001).

CONCLUSIONS

Administration of CAD via HFNC/VMN led to a greater than fourfold increase in drug delivery compared to LVN with FM. Optimal aerosol delivery occurred at 3 L/minute with SML Adult HFNC.

In vitro evaluation of aerosol drug delivery with and without high flow nasal cannula in children

OBJECTIVE

To quantify aerosol delivery with or without a high flow nasal cannula (HFNC) in place using pressurized metered-dose inhaler (pMDI) and jet nebulizer (JN) with facemask in a simulated spontaneously breathing pediatric lung model.

METHODS

An upper airway model of a 9-month-old infant (Sophia Anatomical Infant Nose-Throat) with an absolute filter distal to the trachea was connected to a breathing simulator to simulate pediatric parameters (tidal volume = 100 mL, respiratory rate = 30 breaths/min, and I:E ratio = 1:1.4). Oxygen at 3 L/min was administered through an infant HFNC (Fisher & Paykel Healthcare Ltd, Auckland, New Zealand) attached to the nares of the model. Albuterol sulfate (2.5 mg/3 mL) was delivered with JN attached to an aerosol facemask and powered by air at 8 L/min. Ventolin Hydrofluoroalkane (HFA) (360 μg) was administered using pMDI connected to a valved holding chamber (VHC) with a facemask. Aerosol was administered to the model with and without HFNC in the nares (n = 3). Drug was eluted from the filter and quantified using spectrophotometry. Independent t tests were performed for data analysis (P < .05).

RESULTS

Aerosol deposition was greater without HFNC (6.05% ± 1.53% and 39.54% ± 8.98% for JN and pMDI/VHC, respectively) than with HFNC using JN (2.91% ± 0.23%; P = .024) and pMDI/VHC (6.04% ± 0.28%; P = .003). Delivery efficiency of pMDI/VHC was greater than JN with or without nasal cannula in place (P = .0001 and .003, respectively).

CONCLUSION

Aerosol administered via facemask over HFNC was less efficient than removing HFNC during administration. When delivering medical aerosol by facemask, the benefit of increased aerosol delivery must be weighed against the changes in oxygen delivery and risk of lung derecruitment when nasal prongs are removed.

Effect of nebulizer type, delivery interface, and flow rate on aerosol drug delivery to spontaneously breathing pediatric and infant lung models

BACKGROUND

Different types of nebulizers, interfaces, and flow rates are used to deliver aerosolized medications to children. The purpose of this study was to determine the effect of nebulizer type, delivery interface, and flow rate on aerosol drug delivery to spontaneously breathing pediatric and infant lung models.

METHODOLOGY

A teaching mannequin was attached to a sinusoidal pump via a collecting filter at the bronchi to simulate a spontaneously breathing child (Vt: 250 mL, RR: 20 bpm and Ti: 1 second) and infant (Vt = 100 mL, RR = 30 bpm, Ti: 0.7 seconds). Albuterol sulfate was nebulized with jet (Misty Max 10; Cardinal Health) and mesh (Aerogen Solo; Aerogen) nebulizers using a low-flow nasal cannula (LFNC; Hudson), a high-flow nasal cannula (HFNC; Fisher & Paykel), face mask (FM; Hudson), and mouthpiece (MP; Cardinal Health). While all interfaces were used in the pediatric study, only LFNC, HFNC, and FM were tested in the infant study. The mesh nebulizer was tested at 2, 4, and 6 L/min with LFNC, 4 and 6 L/min with HFNC, and 6 L/min with FM and MP. The jet nebulizer was operated at 6 and 8 L/min with FM and 6 L/min with LFNC, HFNC, and MP (n = 5). The drug was eluted from the filter and analyzed by spectrophotometry. Factorial analysis of variance and post hoc comparisons were used for data analysis. P < .05 was considered statistically significant.

RESULTS

Delivery efficiency of mesh nebulizers is two to fourfold more than jet nebulizers used with HFNC, FM, and MP. No statistical difference was found between jet and mesh nebulizers used with LFNC in infants (P = .643) and pediatrics (P = .255). Aerosol delivery with MP was the best compared to other interfaces used in pediatrics (P < .05). As the second-best interface in aerosol drug delivery, the delivery efficiency of FM was greater than HFNC (P = .0001) and LFNC (P = .0001). Increasing flow rate with LFNC and HFNC decreased aerosol delivery with the mesh nebulizer in both infants and pediatrics.

CONCLUSION

The type of nebulizer, delivery interface, and flow rate used in the treatment of children affect aerosol drug delivery.

Mesh nebulizer is as effective as jet nebulizer in clinical practice of acute asthma in children

Background/aim

The aim of this study was to compare the effect of salbutamol delivered to children by jet nebulizer (JN) and mesh nebulizer (MN).

Materials and methods

Children admitted with acute asthma were treated with 3 doses of nebulized salbutamol, 1 given by MN. The patients’ vital signs, lung function measurements, modified pulmonary index score (MPIS), and whole body plethysmography (WBP) measurements were evaluated before and 20 min after each dose of salbutamol.

Results

Thirty-onechildren [9.5 (6.4–17.2) years, 67.7% male, 32.3% female] with mild (67.7%) and moderate (32.3%) asthma attacks were included in the study. The improvements with MN were comparable with JN in terms of changes in pretreatment and posttreatment forced expiratory volume in the first second (FEV1) (2.57 ± 4.57, 3.65 ± 5.44; P = 0.44), forced vital capacity (FVC) (2.52 ± 5.29, 4.17 ± 7.54; P = 0.28), heart rate (7.33 ± 10.21, 4.14 ± 9.32; P = 0.24), peripheral capillary oxygen saturation (SpO2) (0.38 ± 0.23, 0.43 ± 0.15; P = 0.83), and modified pulmonary index score (MPIS) (−6.30 ± 22.70, −8.77 ± 25.46; P = 0.70). The pre- and posttreatment values of total lung capacity (TLC), residual volume (RV), specific conductance (sGaw), and RV/TLC were similar for the JN and MN groups. Adverse effects were not different: however, complaints of palpitation were significantly higher in the posttreatment MN group than the pretreatment MN group (32.3% vs 9.7%, respectively, P = 0.016).

Conclusions

These findings support the previous evidence found in studies of adults that MN is as effective as and as safe as JN in the treatment of acute asthma in children.

Medical devices and the pediatric population - a head-to-toe approach

Introduction: This review uses a head-to-toe approach, a standardized approach similar to the format used by clinicians during the physical examination, to highlight important differences between children, adolescents and adults. The assessment of a pediatric patient is significantly different from an adult and the heterogeneity of the pediatric population requires knowledge of the inter- and intra-subpopulation differences in growth and development for all organ systems. Areas covered: A search of the English medical literature (PubMed and EMBASE) resulted in identification and review of articles that reported medical device use in the pediatric population based on specific organ systems. The review highlights unique considerations for the pediatric population with respect to growth and development as well as important physiologic and maturational differences between children and adults pertaining to the use of medical devices. Expert opinion: Children have unique medical device needs; adult devices are often adapted or configured to address these unmet needs. It is important that clinicians, and those who manufacture and design medical devices for the pediatric population, have a heightened awareness of the varied pediatric subpopulations (neonates to adolescents) with respect to growth and development, and the adjustments needed to ensure safe and effective use of devices for their unique needs.

Decrease the flow setting to improve trans-nasal pulmonary aerosol delivery via "high-flow nasal cannula" to infants and toddlers

OBJECTIVES

Trans-nasal pulmonary aerosol delivery for infants and toddlers has recently gained popularity, however, the reported lung deposition is low. We aimed to investigate the influential factors to improve the delivery.

METHODS

Anatomic airway manikins simulating infant (5 kg) and toddler (15 kg) with collecting filter connected the trachea and breath simulator, were set to represent quiet and distressed breathing. Nasal cannula flow was set at 0.125, 0.25, 0.5, 1, and 2 L/kg/min. A mesh nebulizer (Aerogen) was placed at the inlet of humidifier (Fisher & Paykel) and proximal to patient. Albuterol (5 mg in 1 mL) was nebulized for each condition (n = 3). Drug was eluted from the filter and assayed with UV spectrophotometry (276 nm).

RESULTS

Inhaled dose was higher with nebulizer placed at the inlet of humidifier than proximal to patient in all settings, except the infant model at low gas flow settings (0.125 and 0.25 L/kg/min). When nebulizer was placed at the inlet of humidifier, inhaled dose was higher when gas flow was below patient's inspiratory flow than when gas flow exceeded patient's inspiratory flow (8.77 ± 3.84 vs 2.16 ± 1.29%, P < 0.001); aerosol deposition increased as gas flow decreased, with greatest deposition at gas flow of 0.25 L/kg/min (11.29 ± 2.15%). A multiple linear regression identified gas flow as the primary predictor of aerosol delivery.

CONCLUSIONS

Trans-nasal pulmonary aerosol delivery was significantly improved when gas flow was below patient's inspiratory flow, aerosol deposition increased with decreased nasal cannula flow, with greatest deposition at 0.25 L/kg/min.

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.

Aerosol therapy through high flow nasal cannula in pediatric patients

INTRODUCTION

High flow nasal cannula (HFNC) is increasingly used in pediatric patients suffering from respiratory failure. In some disease processes, patients may also benefit from aerosol therapy. Therefore, the use of HFNC to deliver aerosolized medications is a convenient and attractive option. Areas covered: This review aims to appraise available evidence concerning the efficiency of aerosol nebulized therapy delivery using HFNC in pediatric patients. Expert commentary: Delivery of aerosol particles is a very complex process and depends on the use of oxygen vs. heliox, nebulizer type and position within the HFNC circuit, patient's breathing effort and pattern, and more importantly cannula size and flow rates. Current in vitro evidence suggests the amount of aerosol delivery is likely to be very low at high flows. Clinical studies are limited in pediatric patients and given the limited clinical data, it is not possible to make recommendations for or against aerosol delivery through HFNC for pediatric patients.

Nasal high flow nebulization in infants and toddlers: An in vitro and in vivo scintigraphic study

Aerosol therapy in infants and toddlers is challenging. Nebulization within a nasal high flow (NHF) circuit is attractive. The aim of this study was to quantify aerosol lung deposition when combined with NHF as compared with standard practice. Lung doses were measured scintigraphically after nebulization with jet and mesh nebulizer placed within a NHF circuit in a spontaneously breathing non-human primate model (macaque) and in the anatomical bench SAINT model, respectively representing a full-term newborn and a 9-month-old toddler. In the SAINT model, lung depositions observed with the mesh nebulizer placed in the NHF circuit set at 2 and 4 L/min were 3.3% and 4.2% of the nebulizer charge, respectively, and similar to the 1.70% observed with the control standard facemask jet nebulization (6 L/min flow). In the macaque model, the depositions observed with the mesh nebulizer in the NHF circuit set at 2 and 4 L/min were 0.49% and 0.85%, respectively, also similar to the control measurement (0.71%). Mesh nebulization within a NHF circuit set at 8 L/min and jet nebulization either within a NHF circuit or placed on top of the cannula (NHF set at 2 L/min; total flow of 8 L/min), resulted in a significantly lower lung depositions. Mesh nebulization within a NHF circuit delivering up to 4 L/min gas is likely to be at least as effective than jet nebulization with a facemask in infants and toddlers. Aerosol facemask placement on top of cannulas or jet nebulization within the NHF circuit may be less effective. Pediatr Pulmonol. 2017;52:337-344. © 2016 Wiley Periodicals, Inc.

Drug delivery interfaces: A way to optimize inhalation therapy in spontaneously breathing children

There are several different types of drug delivery interfaces available on the market. Using the right interface for aerosol drug delivery to children is essential for effective inhalation therapy. However, clinicians usually focus on selecting the right drug-device combination and often overlook the importance of interface selection that lead to suboptimal drug delivery and therapeutic response in neonates and pediatrics. Therefore, it is necessary to critically assess each interface and understand its advantage and disadvantages in aerosol drug delivery to this patient population. The purpose of this paper is to provide a critical assessment of drug delivery interfaces used for the treatment of children with pulmonary diseases by emphasizing advantages and problems associated with their use during inhalation therapy.

Creation of a protective pulmonary bioshield against inhaled organophosphates using an aerosolized bioscavenger

In addition to the global use of organophosphate (OP) pesticides for agriculture, OP nerve agents and pesticides have been employed on battlefields and by terrorists (e.g., a recent sarin attack in Syria). These occurrences highlight the need for an effective countermeasure against OP exposure. Human butyrylcholinesterase (HuBChE) is a leading candidate, but injection of the high doses required for protection present pharmacokinetic challenges. An aerosolized recombinant form (aer-rHuBChE) that can neutralize inhaled OPs at the portal of entry has been assessed for its efficacy in protecting macaques against respiratory toxicity following inhalation exposure to the pesticide paraoxon (aer-Px). While protection in macaques has been demonstrated using the MicroSprayer® delivery device, administration to humans will likely employ a vibrating mesh nebulizer (VMN). Compared to the 50-70% lung deposition achieved in adult humans with a VMN, deposition in macaques is <5%, an initial major obstacle to demonstrating protection. Such problems have been partly overcome by using a more efficient modified VMN and proportionally higher doses, which together generate an effective rHuBChE pulmonary bioshield and protect against high levels of inhaled Px.

Computational Models of Inhalation Therapy in Early Childhood: Therapeutic Aerosols in the Developing Acinus

BACKGROUND

Inhalation therapy targeted to the deep alveolated regions holds great promise, specifically in pediatric populations. Yet, inhalation devices and medical protocols are overwhelmingly derived from adult guidelines, with very low therapeutic efficiency in young children. During the first years of life, airway remodeling and changing ventilation patterns are anticipated to alter aerosol deposition with underachieving outcomes in infants. As past research is still overwhelmingly focused on adults or limited to models of upper airways, a fundamental understanding of inhaled therapeutic transport and deposition in the acinar regions is needed to shed light on delivering medication to the developing alveoli.

METHODS

Using computational fluid dynamics (CFD), we simulated inhalation maneuvers in anatomically-inspired models of developing acinar airways, covering the distinct phases of lung development, from underdeveloped, saccular pulmonary architectures in infants, to structural changes in toddlers, ultimately mimicking space-filling morphologies of a young child, representing scaled-down adult lungs. We model aerosols whose diameters span the range of sizes acknowledged to reach the alveolar regions and examine the coupling between morphological changes, varying ventilation patterns and particle characteristics on deposition outcomes.

RESULTS

Spatial distributions of deposited particles point to noticeable changes in the patterns of aerosol deposition with age, in particular in the youngest age group examined (3 month). Total deposition efficiency, as well as deposition dispersion, vary not only with the phases of lung development but also and critically with aerosol diameter.

CONCLUSIONS

Given the various challenges when prescribing inhalation therapy to a young infant, our findings underline some mechanistic aspects to consider when targeting medication to the developing alveoli. Not only does the intricate coupling between acinar morphology and ventilation patterns need to be considered, but the physical properties (i.e., aerodynamic size) of therapeutic aerosols also closely affect the anticipated success rates of the inhaled medication.

Optimization and Dose Estimation of Aerosol Delivery to Non-Human Primates

BACKGROUND

In pre-clinical animal studies, the uniformity of dosing across subjects and routes of administration is a crucial requirement. In preparation for a study in which aerosolized live-attenuated measles virus vaccine was administered to cynomolgus monkeys (Macaca fascicularis) by inhalation, we assessed the percentage of a nebulized dose inhaled under varying conditions.

METHODS

Drug delivery varies with breathing parameters. Therefore we determined macaque breathing patterns (tidal volume, breathing frequency, and inspiratory to expiratory (I:E) ratio) across a range of 3.3-6.5 kg body weight, using a pediatric pneumotachometer interfaced either with an endotracheal tube or a facemask. Subsequently, these breathing patterns were reproduced using a breathing simulator attached to a filter to collect the inhaled dose. Albuterol was nebulized using a vibrating mesh nebulizer and the percentage inhaled dose was determined by extraction of drug from the filter and subsequent quantification.

RESULTS

Tidal volumes ranged from 24 to 46 mL, breathing frequencies from 19 to 31 breaths per minute and I:E ratios from 0.7 to 1.6. A small pediatric resuscitation mask was identified as the best fitting interface between animal and pneumotachometer. The average efficiency of inhaled dose delivery was 32.1% (standard deviation 7.5, range 24%-48%), with variation in tidal volumes as the most important determinant.

CONCLUSIONS

Studies in non-human primates aimed at comparing aerosol delivery with other routes of administration should take both the inter-subject variation and relatively low efficiency of delivery to these low body weight mammals into account.

Nanopolymersomes as potential carriers for rifampicin pulmonary delivery

Tuberculosis (TB) has been stated as "the greatest killer worldwide due to a single infectious agent" behind the human immunodeficiency virus. Standard short-term treatment includes the oral administration of a combination of "first-line" drugs. However, poor-patient compliance and adherence to the long-term treatments represent one of the mayor drawbacks of the TB therapy. An alternative to the oral route is the pulmonary delivery of anti-TB drugs for local or systemic administration. Nanotechnology offers an attractive platform to develop novel inhalable/respirable nanocarriers. The present investigation was focused on the encapsulation of rifampicin (RIF) (a "first-line" anti-TB drug) within nanopolymersomes (nanoPS) employing di- and tri-block poly(ethylene glycol) (PEG)-poly(ɛ-caprolactone) (PCL) based copolymers as biomaterials. The derivatives presented a number-average molecular weight between 12.2 KDa and 30.1 KDa and a hydrophobic/hydrophilic balance between 0.56 and 0.99. The nanoPS were able to enhance the apparent RIF aqueous solubility (up to 4.62 mg/mL) where the hydrodynamic diameters of the drug-loaded systems (1% w/v) were ranged between 65.8 nm and 94 nm at day 0 as determined by dynamic light scattering (DLS). Then, RIF-loaded systems demonstrated as excellent colloidal stability in aqueous media over 14 days with a spherical morphology as determined by transmission electron microscopy (TEM). Furthermore, RIF-loaded nano-sized PS promoted drug accumulation in macrophages (RAW 264.7) versus a drug solution representing promising results for a potential TB inhaled therapy.

Performance Comparisons of Jet and Mesh Nebulizers Using Different Interfaces in Simulated Spontaneously Breathing Adults and Children

BACKGROUND

Different types of nebulizers and interfaces are used for the treatment of adults and children with pulmonary diseases. The purpose of this study was to determine the efficiency of a mesh nebulizer (MN) with a proprietary adapter and a jet nebulizer (JN) under different configurations in adult and pediatric models of spontaneous breathing. We hypothesize that delivery efficiency of JN and MN will differ depending on the interface used during aerosol therapy in simulated spontaneously breathing adult and pediatric models. While we expect that aerosol delivery with JN will be less efficient than MN, we also hypothesize that lung deposition obtained with the adult lung model will be more than that with the pediatric lung model in all conditions tested in this study.

METHODS

A lung model using a teaching manikin connected to a sinusoidal pump via a collecting filter at the level of the bronchi simulating a spontaneously breathing adult (Vt 500 mL, RR 15 bpm, I:E ratio 1:2) or pediatric patient (Vt 150 mL, RR 25 bpm, I:E ratio 1:2). Albuterol sulfate (2.5 mg/3 mL) was aerosolized with JN (Mistymax 10, Airlife) or MN (Aerogen Solo(®), Aerogen) with the Adapter (Aerogen Solo(®) Adapter, Aerogen Ltd, Galway, Ireland) using mouthpiece, aerosol mask, and valved-mask in adults and the dragon mask, aerosol mask, and valved-mask in pediatrics (n=3). The Adapter, specifically designed for MN, was attached to all the interfaces used in this study with supplemental oxygen of 2 lpm, and in addition, the MP was tested with no additional flow in the adult model. The JN was driven with 10 lpm based on the manufacturer's label. Drug was eluted from the filter and analyzed via spectrophotometry. Descriptive statistics, dependent t-test and one-way analysis of variance were used for data analysis. Significant level was set at 0.05.

RESULTS

In adults, delivery efficiency of JN with the valved mask was significantly greater than that with the aerosol mask (p=0.01). Aerosol delivery of JN with the mouthpiece was not statistically significant from the valved mask (p=0.123) and the aerosol mask (p=0.193). Drug delivery with MN with mouthpiece (15.42±1.4%) and valved-mask (15.15±1.1%) was greater than the open aerosol mask (7.54±0.39%; p=0.0001) in the adult lung model. With no flow mouthpiece delivery increased>2 fold (34.9±3.1%; p=.0001) compared to use of 2 lpm of flow. Using the JN with the pediatric model deposition with valved-mask (5.3±0.8%), dragon mask (4.7±0.9%), and aerosol mask (4.1±0.3%) were similar (p>0.05); while drug delivery with MN via valved-mask (11.1±0.7%) was greater than the dragon mask (6.44±0.3%; p=0.002) and aerosol mask (4.6±0.4%; p=0.002), and the dragon mask was more efficient than the open aerosol mask (p=0.009) CONCLUSION: The type of nebulizer and interface used for aerosol therapy affects delivery efficiency in these simulated spontaneously breathing adult and pediatric models. Drug delivery was greatest with the valved-mouthpiece and mask with JN and MN, while the standard aerosol mask was least efficient in these simulated spontaneously breathing adult and pediatric lung models. Delivery efficiency of JN was less than MN in all conditions tested in this study except in the aerosol mask. Lung deposition obtained with the adult lung model was more than that with the pediatric lung model.