Carbon dioxide Assisted Nebulization with a Bubble Dryer((R)) (CAN-BD) processing allows particles to be made in the 3-5 mum size range, which is desirable for lung delivery, without destroying biological activity. In response to the Grand Challenge in Global Health Initiative #3, we have been developing an inhalable needle-free live-attenuated measles virus vaccine for use in developing countries. Measles was chosen because it is the number one vaccine preventable killer of children worldwide. Powders were processed by CAN-BD, where a solution containing excipients and live-attenuated measles virus in water was mixed intimately with supercritical or near superctitical carbon dioxide to form an emulsion. The emulsion was expanded to atmospheric pressure through a flow restrictor. The resulting plume was dried by heated nitrogen and the powders collected on a filter at the bottom of the drying chamber. Powders were analyzed using varying techniques including X-ray diffraction, scanning electron microscopy, Andersen cascade impaction, differential scanning calorimetery, Karl Fischer titration, and viral plaque assay. CAN-BD has been used to produce powders of live-attenuated measles virus vaccine with characteristics desirable for lung delivery. The powders retain viral activity through forming and drying the microparticles by CAN-BD, and have passed the WHO stability test for 1 week at 37 degrees C. The powders have an amorphous character and a glass transition temperature of around 60 degrees C. Lyophilization, the present standard commercial method of processing measles vaccine makes solids with a water content of less than 1%. By substituting myo-inositol for sorbitol and using the CAN-BD drying technique the water content can be lowered to 0.5%. The most successful formulations to date have been based conceptually on the current lyophilized formulation, but with modifications to the type and amounts of sugar. Of current interest are formulations containing myo-inositol, as they retain high viral activity and have low initial water content.
A numerical investigation of a hood inhaler is presented, aiming at the assessment of the amount of aerosol that reaches the eyes of the patient when administrating medications with such a device. Using a hood for aerosol therapy for infants was already found to be effective and friendly to handle over the commonly used face mask. Using a hood device may adversely deliver unwanted medications to the eyes of the infant. The current study addresses the extent of aerosol deposition at the infant's eye zone. We describe the development and utilization of a numerical simulation for studying the transport and fate of the aerosol particles within a 3D realistic representation of the hood and the infant's head, with a focus on the eye zone. The governing equations were solved using the commercial software, FLUENT 6.1, which is based on the finite volume method. The computational domain was created using the GAMBIT package. The computational geometry was built separately for each configuration of the hood and the infant. It is shown that under optimal working conditions (i.e., when the infant's head is aligned to the funnel) the percentage of aerosol reaching the eye zone is 0.48%. However, when the funnel is tilted toward the eyes the amount of aerosol reaching the eyes zone is predicted to be 4.7%. In general, the results obtained in this study are in good agreement with available in vitro data. It can be concluded that using the hood for aerosol therapy results in minimal deposition at the infant's eye area.
Proteases and antiproteases have multiple important roles both in normal homeostasis and during inflammation. Antiprotease molecules may have developed in a parallel network, consisting of "alarm" and "systemic" inhibitors. Their primary function was thought until recently to mainly prevent the potential injurious effects of excess release of proteolytic enzymes, such as neutrophil elastase (NE), from inflammatory cells. However, recently, new potential roles have been ascribed to these antiproteases. We will review "canonical" and new "noncanonical" functions for these molecules, and more particularly, those pertaining to their role in innate and adaptive immunity (antibacterial activity and biasing of the adaptive immune response).
There is an increasing interest in using the lung as a route of entry for both local and systemic administration of drugs. However, because adequate technologies have been missing in the preclinical setting, few investigators have addressed the detailed disposition of drugs in the lung following short inhalation exposures to highly concentrated dry powder aerosols. New methods are needed to explore the disposition of drugs after short inhalation exposures, thus mimicking a future clinical use. Our aim was to study the pulmonary disposition of budesonide, formoterol, and terbutaline, which are clinically used for the treatment of bronchial asthma. Using the recently developed DustGun aerosol technology, we exposed by inhalation for approximately 1 min the isolated and perfused rat lung (IPL) to respirable dry particle aerosols of the three drugs at high concentrations. The typical aerosol concentration was 1 mug/mL, and the particle size distribution of the tested substances varied with a MMAD ranging from 2.3 to 5.3 mum. The IPL was perfused in single pass mode and repeated samples of the perfusate were taken for up to 80 min postexposure. The concentration of drug in perfusate and in lung extracts was measured using LC-MS/MS. The deposited dose was determined by adding the amounts of drug collected in perfusate to the amount extracted from the tissues at 80 min. Deposited amounts of budesonide, formoterol fumarate, and terbutaline sulphate were 23 +/- 17, 36 +/- 8, and 60 +/- 3.2 mug (mean +/- SD, n = 3), respectively. Retention in lung tissues at the end of the perfusion period expressed as fraction of deposited dose was 0.19 +/- 0.05, 0.19 +/- 0.06, and 0.04 +/- 0.01 (mean +/- SD, n = 3) for budesonide, formoterol, and terbutaline, respectively. Each short inhalation exposure to the highly concentrated aerosols consumed 1-3 mg powder. Hence, this system can be particularly useful for obtaining a detailed pharmacokinetic characterization of inhaled compounds in drug discovery/development.
Prostacyclin and prostacyclin analogues are potent vasodilators and possess antithrombotic, anti-inflammatory and antiproliferative properties. These properties qualify them as efficient drugs for the treatment of pulmonary hypertension, a life-threatening illness characterized by an increase in artery pressure and vascular resistance in the pulmonary circulation. Diseased pulmonary vessels show specific remodeling with intimal fibrosis, medial hypertrophy, and adventitial thickening, as well as functional changes characterized by vasoconstriction and in situ thrombosis. The intravenous administration of prostacyclin is a well-established therapy option in severe pulmonary hypertension. However, lack of pulmonary and intrapulmonary selectivity can lead to life-threatening pulmonary and systemic side effects. Therefore, the application of prostanoids by inhalation had been proposed. Several studies with inhaled iloprost, a stable prostacyclin analogue, demonstrated preferential and potent vasorelaxation in the pulmonary circulation. In a randomized, double-blind, placebo controlled, multicenter study in 203 patients with pulmonary hypertension inhaled iloprost showed significant improvement of exercise capacity and pulmonary hemodynamics with excellent tolerability and safety. Consequently, inhaled iloprost has been approved in many countries for treatment of severe pulmonary hypertension. A major drawback of inhaled iloprost, however, is the short half-life and hemodynamic effect (30 to 60 min) demanding multiple daily inhalation manoeuvres (up to nine times). Strategies for further improvement of inhaled prostanoid therapy include use of prostacyclin analogues with longer half-life (e.g., treprostinil), combinations with oral drugs (e.g., phosphodiesterase inhibitors or endothelin receptor antagonists) and development of aerosolized controlled release formulations such as liposomes and nanoparticles. The therapy with prostacyclin and its analogues is a main pillar in the treatment of pulmonary hypertension, giving new hope to many patients suffering from this terrible disease. With inhaled iloprost, a new drug has enlarged the scope of aerosol therapies for treatment of pulmonary and systemic diseases.
Exhaled breath condensate (EBC) consists mainly of water, but also contains semivolatile and nonvolatile compounds. The aim of this study was to develop a system in which two condensers are simultaneously used in series to clarify the mechanisms of EBC condensation. Two aliquots of EBC (EBC1 and EBC2) were collected from 20 asymptomatic smokers and 20 healthy young nonsmokers using a specifically designed device having two condensers in series in which total volume, hydrogen peroxide (H(2)O(2)), ammonium (NH(4)(+)), and conductivity before and after lyophilization were measured. Water, NH(4)(+) levels and conductivity before lyophilization were significantly lower in the EBC2 than in the EBC1 of smokers and nonsmokers; the contrary was true for H(2)O(2) levels. Almost all nonvolatile salts were collected in the first condenser, because more than 50% of postlyophilization conductivity was below the detection limit in EBC2. The recovery of volatile molecules and their derivatives (water and NH(4)(+)) was partial in the first condenser, but appreciable amounts of both were measured in the second; however, the condenser immediately in contact with exhaled air was more efficient in terms of water, NH(4)(+) and conductivity before lyophilization. On the contrary, nonvolatile ions (conductivity after lyophilization) were mainly collected in the first condenser. Finally, the behavior of H(2)O(2) cannot be explained on the basis of its chemical and physical properties, and the most probable explanation is that some was byproduced by a radical reaction in the gas phase or during the condensation process in water.
Regional chemotherapy has been proposed as a treatment modality in a number of cancer settings. In primary or metastatic lung cancer, administration of chemotherapy via inhalation could increase exposure of lung tumor to the drug, while minimizing systemic side effects. Several proof of concept studies in animal models of metastatic or primary lung cancer have demonstrated the safety, pharmacokinetic advantage, and antitumor effect of aerosol administration of several chemotherapeutic agents including doxorubicin, gemcitabine and liposome-encapsulated formulations of paclitaxel and 9-nitrocamptothecin (9-NC). Recent phase I studies have demonstrated the feasibility of aerosol delivery of doxorubicin and liposomal formulations of 9-NC and cisplatin in patients with primary and metastatic lung cancer with a limited pharmacokinetic profile consistent with the observed low systemic toxicity. Further studies integrating safety, pharmacokinetic, and efficacy considerations are required to determine whether there is a place for local administration of chemotherapy via inhalation in lung cancer.
Bronchodilators are frequently used in ICU patients, and are the most common medications administered by inhalation during mechanical ventilation. The amount of bronchodilator that deposits at its site of action depends on the amount of drug, inhaled mass, deposited mass, and particle size distribution. Mechanical ventilation challenges both inhaled mass and lung deposition by specific features, such as a ventilatory circuit, an endotracheal tube, and ventilator settings. Comprehensive in vitro studies have shown that an endotracheal tube is not as significant a barrier for the drug to travel as anticipated. Key variables of drug deposition are attachments of the inhalation device in the inspiratory line 10 to 30 cm to the endotracheal tube, use of chamber with metered-dose inhaler, dry air, high tidal volume, low respiratory frequency, and low inspiratory flow, which can increase the drug deposition. In vivo studies showed that a reduction by roughly 15% of the respiratory resistance was achieved with inhaled bronchodilators during invasive mechanical ventilation. The role of ventilatory settings is not as clear in vivo, and primary factors for optimal delivery and physiologic effects were medication dose and device location. Nebulizers and pressurized metered-dose inhalers can equally achieve physiologic end points. The effects of bronchodilators should be carefully evaluated, which can easily be done with the interrupter technique. With the non-invasive ventilation, the data regarding drug delivery and physiologic effects are still limited. With the bilevel ventilators the inhalation device should be located between the leak port and face mask. Further studies should investigate the effects of inhaled bronchodilators on patient outcome and methods to optimize delivery of inhaled bronchodilators during non-invasive ventilation.
Epidemiological studies show a clear link between increased mortality and enhanced concentrations of ambient aerosols. The chemical and physical properties of aerosol particles causing these health effects remain unclear. A major fraction of the ambient aerosol particle mass is composed of secondary organic aerosol (SOA). Recent studies showed that a significant amount of SOA consists of high molecular weight compounds (oligomers), which are chemically not well characterized. Within the POLYSOA project a large variety of state-of-the-art analytical chemical methods were used to characterize the chemical composition of SOA particles with emphasis on the oligomeric mass fraction. Mass spectrometric results showed that SOA oligomers are highly oxidized compounds and that hydroperoxides are formed, which is consistent with NMR results. This high molecular weight fraction accounts for up to 23% of the total organic carbon in SOA particles. These well-characterized SOA particles were deposited on three lung cell culture systems (microdissected respiratory epithelia from porcine tracheae, the human bronchial epithelial cell line BEAS-2B, and porcine lung surface macrophages obtained by bronchoalveolar lavage) in a newly constructed particle deposition chamber with the goal to eventually identify particle components that are responsible for cell responses leading to adverse health effects. In addition, monolayers of the alveolar epithelial cell line A549 were used in an alveolar epithelial repair model. The lung cells were examined for morphological, biochemical, and physiological changes after exposure to SOA. Analyses of the lung cells after exposure to SOA are ongoing. First data give evidence for a moderate increase of necrotic cell death as measured by lactate dehydrogenase release and for effects on the alveolar epithelial wound repair mainly due to alterations of cell spreading and cell migration at the edge of the wound. Thus, these first results indicate that SOA, in concentrations comparable to environmental concentrations, may induce distinct effects in lung cells.
There are strong data supporting using the use of aerosolized antibiotics for the treatment of Gram-negative infections in patients with cystic fibrosis (CF). The regular use of aerosol tobramycin or colistin can decrease exacerbations of lung disease, decrease bacteria counts, and improve pulmonary function in persons with CF and Pseudomonas aeruginosa airway infection. Bronchiectasis is caused by reoccurring or continuous presence of bacteria in association with airway obstruction. Although CF is the most common cause of childhood bronchiectasis, there are many other causes. Because secretions in the bronchiectasis airway are similar to the pus found in the CF airway, and because pulmonary complications and progression of disease in non-CF bronchiectasis is similar to CF bronchiectasis, many centers treat patients with bronchiectasis using aerosolized tobramycin solution for inhalation (TSI). There have been only a few small studies of aerosolized antibiotics to treat pseudomonas infection in subjects with non-CF bronchiec.tasis. Unlike the CF experience, there does not seem to be an improvement of pulmonary function after treatment with aerosol tobramycin in this population despite a decreased sputum bacterial density and a trend toward a decrease in risk of hospitalization. Furthermore, the risk of adverse events such as bronchospasm may be more common in adults with non-CF bronchiectasis than reported in the CF population.
Pressurized metered-dose inhalers (pMDIs) and nebulizers are routinely employed for aerosol delivery in mechanically ventilated patients. A significant proportion of the aerosol deposits in the ventilator circuit and artificial airway, thereby reducing the inhaled drug mass. Factors influencing aerosol delivery during mechanical ventilation differ from those in spontaneously breathing patients. The English language literature on aerosol delivery during mechanical ventilation was reviewed. Marked variations in the efficiency- of drug delivery with pMDIs and nebulizers occur due to differences in the technique of administration. Careful attention to five factors, viz., the aerosol generator, aerosol particle size, conditions in the ventilator circuit, artificial airway, and ventilator parameters, is necessary to optimize aerosol delivery during mechanical ventilation. Factors influencing drug delivery during NPPV are not well understood, and the efficiency of aerosol delivery in. this setting is lower than that during invasive mechanical ventilaiton. With an optimal technique of administration the efficiency of aerosol delivery during mechanical ventilation is similar to that achieved during spontaneous breathing. Further research is needed to optimize aerosol delivery during NPPV.
Mucociliary clearance is an important primary innate defense mechanism that protects the lungs from deleterious effects of inhaled pollutants, allergens, and pathogens. Mucociliary dysfunction is a common feature of chronic airway diseases in humans. The mucociliary apparatus consists of three functional compartments, that is, the cilia, a protective mucus layer, and an airway surface liquid (ASL) layer, which work in concert to remove inhaled particles from the lung. A synopsis of clinical and pathological observations in patients with cystic fibrosis, primary ciliary dyskinesia, asthma, and chronic bronchitis indicates that abnormalities in each compartment of the mucociliary system can compromise mucus clearance and cause chronic airway disease. However, the mechanisms that lead to deficient mucus clearance are still incompletely understood. Genetically engineered mice with defects in individual elements of the mucociliary apparatus are powerful tools to study the pathogenesis of mucociliary dysfunction in vivo. In this concise review, I assess the pulmonary phenotypes of mouse models with genetically defined abnormalities in ciliary structure/function, mucus production, and ASL regulation, and discuss the results of these animal studies in the context of current pathogenetic hypotheses for mucociliary dysfunction. Recent data driven from these animal studies point to a critical role of ASL dehydration in the pathogenesis of mucociliary dysfunction and chronic airway disease. In mice with airway-specific overexpression of epithelial Na(+) channels (ENaC), which constitute a rate limiting pathway for absorption of salt and water from airway surfaces, ASL depletion caused reduced mucus clearance, and a spontaneous chronic airway disease with mucus obstruction, goblet cell metaplasia, chronic inflammation, reduced bacterial clearance, and high pulmonary mortality. This mouse model of mucociliary dysfunction will allow an in vivo evaluation of novel therapeutic strategies designed to improve mucociliary clearance, and will aid the preclinical development of novel therapies for chronic airway diseases.
Aerosol mixing resulting from turbulent flows is thought to be a major mechanism of deposition in the upper respiratory tract (URT). Because turbulence levels are a function of gas density, the use of a low-density carrier gas should reduce deposition in the URT allowing the aerosol to reach more peripheral airways of the lung. We performed aerosol bolus tests on 11 healthy subjects to investigate the effect of reduced gas density on regional aerosol deposition in the human lung. Using both air and heliox (80% helium, 20% oxygen) as carrier gas, boluses of 1 and 2 microm-diameter particles were inhaled to five volumetric lung depths (V(p)) between 150 and 1200 mL during an inspiration from residual volume (RV) to 1 liter above functional residual capacity at a constant flow rate of approximately 0.50 L/sec, which was immediately followed by an expiration to RV at the same flow rate. Aerosol deposition and axial dispersion were calculated from aerosol concentration and flow rate measured at the mouth. For 1 microm-diameter particles, deposition was significantly reduced by 29 +/- 28% (mean +/- SD, p < 0.05) when breathing heliox instead of air at shallow V(p) (150 mL) and significantly increased by 11 +/- 9% at deep V(p) (1200 mL). For 2 microm-diameter particles, deposition was significantly higher at V(p) = 500 mL by 6 +/- 7% and the predicted V(p) to achieve 100% deposition was significantly lower with heliox (834 +/- 146 mL) compared to air (912 +/- 128 mL) (p < 0.05). Despite a decrease in deposition at shallow V(p), there was no change in axial dispersion, suggesting that other factors such as radial turbulent mixing result in decreased aerosol deposition. Our results suggested that heliox reduces upper airway deposition of 1 and 2 microm-diameter particles allowing more particles to penetrate and subsequently deposit in the peripheral lung.
Animal models are essential for understanding the fates and effects of inhaled materials, because invasive methods are frequently necessary to provide the desired information. Because of the variability in humans of particle deposition, clearance, and effects, numerous animal models have been used in inhalation studies. Furthermore, humans are not typical mammals in some ways that affect inhalation phenomena. Humans have less fur, longer gestation and life times, simplified nasal structure, and symmetric bronchial branching in relation to other mammals. However, experience, plus the genetic similarity among mammals, underpins the use of animal models. Mammals are varied with respect to their inhaled particle deposition and clearance phenomena. Total inhaled aerosol deposition probability versus particle-size curves are qualitatively similar for various mammals of similar body mass, despite airway anatomy differences. However, more species variation is seen in regional particle deposition curves, complicating aerosol study design. The rates of clearance of deposited slowly dissolving particles are animal species dependent, apparently due to differences in gross, subgross, and cellular respiratory tract biology. Clearance rates for rapidly dissolving particles are not strongly species dependent. Inhalation toxicology studies require several animal species. Rodents are among the most frequently used, but for studies of lung development, diseases, exercise, etc., and for extrapolation to humans, larger mammals are also needed. Fortunately, the research database, and excellent monographs on inhalation phenomena provide ample guidance for study design.
Establishing clear relationships between in vitro and in vivo data for inhaled drug products is an important goal. In vitro aerodynamic particle size distributions (APSDs) are expected to have some predictive power not only for drug deposition, but also for clinical effects. APSD data obtained by cascade impaction have been compared with lung deposition data measured in gamma scintigraphy studies. Whole-lung deposition correlated significantly with fine particle fraction (FPF) across a range of inhaler devices. FPF, defined in terms of aerosol <5.8 microm or <6.8 microm diameter, systematically overestimated lung deposition for virtually all inhalers. Lung deposition showed closer numerical equivalence to the percentage of the aerosol dose smaller than 3 microm diameter. Correlations exist between APSD data and whole-lung deposition, which may allow the greater use of APSD data for comparing inhaler devices. Agreement between in vitro and in vivo data may be improved by measuring APSD in ways that more closely mimic clinical use, including the use of impactor inlets that simulate the human upper airway anatomy. At the present time there are few published data that relate APSD to the clinical response of inhaled drugs in an unambiguous way.
The laboratory evaluation of inhalers with facemasks for patient interface is so complex that testing without a facemask is generally undertaken, a practice that has been advocated in one standard. However, the facemask itself can profoundly influence medication delivery. A systematic review of the literature was undertaken to establish the development history of face models for the evaluation of facemasks used with inhalers and accessories. Initial attempts to simulate the facemask-face boundary employed a circular, firm rubber flange plate upon which the facemask was located. However, such models did not represent dead volume accurately, which is particularly important when assessing infant use. Subsequent developments included the creation of more realistic facial features, enabling the aerosol leaving the inhaler to be quantified at the facemask. In one instance (SAINT model), an anatomically correct nasopharyngeal cavity has been combined with a model face, enabling assessment of medication delivery to be extended to the lower respiratory tract. However, it is necessary either to apply sealants or to compress the facemask beyond normal to eliminate leakage with the rigid facial structure that is incomplete above the bridge of the nose. An oral-breathing infant full-face model (ADAM) intended to be used to quantify emitted mass at the patient interface incorporates flexible facial features to overcome this limitation. There is a need to extend the flexible face approach to other models that may be developed in the future for testing facemasks, whether or not they incorporate anatomically correct realizations of the upper respiratory tract.
Accurate prediction of respiratory tract deposition is important in gauging the health risks of ambient bioaerosols and environmental aerosols, as well as in developing pharmaceutical aerosols for drug delivery. The present article highlights recent advances in the prediction of total, extrathoracic, and lung deposition fractions of inhaled aerosols over a broad range of parameters for both oral and nasal breathing. These advances build on recent data from in vivo and in vitro studies that have benefited from recent improvements in high-resolution imaging, rapid prototyping, and computational simulation abilities that have significantly enhanced the current understanding of respiratory tract deposition. It is anticipated that the relatively simple equations for predicting total or whole lung deposition that follow from the recent work discussed herein will allow for improved correlation between respiratory tract deposition and a wide range of health outcomes.
The output and particle size distribution of several series of aqueous solutions were measured to define quantitatively the practical limits of the solution properties acceptable for aerosol production by the aeroneb micropump nebulizer. Aerosol output measurements were made gravimetrically and the particle size distributions were obtained by laser diffractometry. Solution properties were obtained from the literature by interpolation of the best-fit curve of the property plotted as a function of composition. For nonionic solutes, addition of sodium chloride dramatically increased the output rate and also decreased the droplet size at low solute concentrations. Increasing viscosity also caused a significant decrease in output. Cesium chloride displayed increased output rate with concentration due to the rising density. Based on calculations with the number of apertures and oscillatory frequency, low output rates appeared to be a consequence of apertures failing to produce a droplet with each oscillation. Overall, ionic strength, density, surface tension, and viscosity affected the output rate in a manner that can be now empirically predicted.
Different approaches have been employed for in vitro assessment of the aerosol particle size generated by inhalation devices. In this study, aerosols from the Omron MicroAir vibrating mesh (VM) nebulizer were measured by cascade impaction (CI) using the MSP Next Generation Pharmaceutical Impactor (NGI), the ThermoAndersen Cascade Impactor (ACI), and by time-of-flight (TOF) analysis with the TSI 3321 Aerodynamic Particle Sizer Spectrometer (APS). The VM nebulizer was evaluated with sodium fluoride (NaF; 2.5%) and with generic albuterol (0.083%). Aerosol particle size (MMAD), respirable fractions (RF < 5 microm), and fine particle fractions (FPF < 3.3 microm) were determined with each method at room temperature (RT) and 4 degrees C using 50% average relative humidity. By NGI at either RT or 4 degrees C, aerosol particle sizes were similar for both NaF and albuterol (4.3-4.5 microm MMAD) with 55-61% RF and 27-43% FPF. With ACI, the distribution of particles at RT was similar except at the extremes of the dispersion and the MMAD was smaller (3.3 microm MMAD; p = 0.03). At 4 degrees C, particle sizes determined by ACI results were similar to the NGI (MMAD 4.1 microm; p > 0.05). TOF analysis by APS with albuterol gave significantly larger calculated MMAD (cMMAD) than either CI method (7.2 microm; p < 0.001). TOF measurements of nebulized albuterol at RT and 4 degrees C were equivalent. In summary, the results of VM nebulized NaF and albuterol were more consistent and generally equivalent when determined by NGI (at RT and 4 degrees C) and ACI analysis (at 4 degrees C). In contrast, aerosol particle sizes measured by TOF in the APS at both RT and 4 degrees C were larger than results obtained by CI. Differences in aerosol particle distribution obtained by different analysis methods should be considered while evaluating the in vitro performance of VM nebulizers.
