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PubMed1991

Drug delivery via aerosol systems: concept of "aerosol inhaled".

The mass of aerosol inhaled is primarily a function of the patient's breathing pattern and the aerosol delivery system. Once inhaled, deposition is governed by factors related to the properties of the aerosol and the individual characteristics of the patient (e.g., particle size distribution, airway geometry, and residence time). This paper will center upon the actual generation and delivery of clinical aerosols by jet nebulizers and assess variability in aerosol delivery. Because of the practical difficulties in predicting nebulizer function from first principles, it will be advocated that nebulizer function be directly measured for each clinical situation. Terms like "nebulizer output", "efficiency", etc. are to be avoided. The following definition is proposed: "aerosol inhaled" represents that quantity of drug actually delivered by a given nebulizer for a defined breathing pattern and period of time. The concept of "aerosol inhaled" allows a direct comparison of the quantity of drug delivered by different nebulizer systems and adjustment of dose of a given therapeutic agent. Bench testing of aerosol systems and measurement of "aerosol inhaled" can be made in the laboratory if careful attention is paid to the relationship between laboratory conditions and actual use, including the particle distribution and the accuracy of a radiolabel in estimating the quantity of drug nebulized.

Administration, Inhalation↗
PubMed2004

Performance of personal inhalable aerosol samplers in very slowly moving air when facing the aerosol source.

While personal aerosol samplers have been characterized primarily based on wind tunnel tests conducted at relatively high wind speeds, modern indoor occupational environments are usually represented by very slow moving air. Recent surveys suggest that elevated levels of occupational exposure to inhalable airborne particles are typically observed when the worker, operating in the vicinity of the dust source, faces the source. Thus, the first objective of this study was to design and test a new, low cost experimental protocol for measuring the sampling efficiency of personal inhalable aerosol samplers in the vicinity of the aerosol source when the samplers operate in very slowly moving air. In this system, an aerosol generator, which is located in the centre of a room-sized non-ventilated chamber, continuously rotates and omnidirectionally disperses test particles of a specific size. The test and reference samplers are equally distributed around the source at the same distance from the centre and operate in parallel (in most of our experiments, the total number of simultaneously operating samplers was 15). Radial aerosol transport is driven by turbulent diffusion and some natural convection. For each specific particle size and the sampler, the aerosol mass concentration is measured by weighing the collection filter. The second objective was to utilize the new protocol to evaluate three widely used aerosol samplers: the IOM Personal Inhalable Sampler, the Button Personal Inhalable Aerosol Sampler and the 25 mm Millipore filter holder (closed-face C25 cassette). The sampling efficiencies of each instrument were measured with six particle fractions, ranging from 6.9 to 76.9 micro m in their mass median aerodynamic diameter. The Button Sampler efficiency data demonstrated a good agreement with the standard inhalable convention and especially with the low air movement inhalabilty curve. The 25 mm filter holder was found to considerably under-sample the particles larger than 10 micro m; its efficiency did not exceed 7% for particles of 40-100 micro m. The IOM Sampler facing the source was found to over-sample compared with the data obtained previously with a slowly rotating, freely suspended sampler in a low air movement environment. It was also found that the particle wall deposition in the IOM metallic cartridge was rather significant and particle size-dependent. For each sampler (IOM, Button and C25) the precision was characterized through the relative standard deviation (RSD) of the aerosol concentration obtained with identical samplers in a specific experiment. The average RSD was 14% for the IOM Sampler, 11% for the Button Sampler and 35% for the 25 mm filter cassette. A separate set of experiments, performed with the Simplified Torso showed that in very slowly moving air a personal sampler can be adequately evaluated even when it is not attached to a body but freely suspended (confirming the data reported previously).

Aerosols↗
PubMed2004

Effect of energy on propylene glycol aerosols using the capillary aerosol generator.

The CAG is being developed for pulmonary drug delivery. Liquids are pumped, heated and vaporized by the CAG, whence they nucleate and condense to form aerosols. This study characterized the effect of energy on the aerosolization process. With increasing energy, the CAG produced an increasing fine particle fraction (FPF) until "optimal aerosolization" was achieved between 40 and 45 J; this energy range agreed with that theoretically required to vaporize the dose of PG. Further increases in energy above this optimal range did not improve PG's aerosolization efficiency. Based on the energy, FPF and temperature profiles, it was possible to deduce the nature of the liquid flow-boiling during aerosol generation. The aerosol particle size went through a minimum, as energy was increased through the "optimal range." In the "energy excess" region, where additional energy increased PG vapor temperature and velocity, droplet sizes were increased primarily due to changes in the nucleation rates and supersaturation ratios affecting the nucleation and condensation processes occurring within the vapor jet. The in vitro MMAD of the PG aerosol changed as a function of the applied energy, suggesting that for any pharmaceutical application, the choice of applied energy is critical to deposition profile of the aerosol.

Administration, Inhalation↗
PubMed1982

Clinical aerosols. I. Characterization of aerosols and their diagnostic uses.

Characterization of an aerosol is of major importance for the understanding of its pathogenic, diagnostic, or therapeutic effect. The parameters necessary for such characterization as well as the methods for obtaining them are reviewed. The factors that determine site of deposition in the human lung are discussed. Further, we have reviewed methods employed to produce aerosols for diagnostic, therapeutic, and clinical research uses. Basic and relatively simple knowledge of aerosol characterization can increase the usefulness of clinical aerosols. Using this knowledge, general principles for aerosol administration are developed. Finally, the application of aerosols in the diagnosis of respiratory diseases is presented; these aerosols include contrast agents, radioactive aerosols, and bronchospastic agents.

Acetylcholine↗
PubMed1985

Drug absorption from inhalation aerosols administered by positive-pressure ventilation. I: Administration of a characterized, solid disodium fluorescein aerosol under a controlled respiratory regime to the beagle dog.

An apparatus and novel method is described for administration of well-characterized inhalation aerosols, under strictly controlled respiratory regimes, direct to the respiratory tract (RT) of the beagle dog by positive-pressure ventilation. The method enables the study of systemic absorption kinetics of compounds delivered as inhalation aerosols as a function of the aerosol particle size and respiratory variables provided their intrinsic pharmacokinetics are linear. Aerosol characteristics are determined by sampling the aerosol at a point close to its entry to the endotracheally intubated animal. The chosen positive-pressure ventilatory regime, which is monitored as airway pressure and exhaled volume versus time, can be held constant for the aerosol administration period. The methodology is illustrated by administration of a solid polydispersed aerosol of disodium fluorescein. Resultant plasma concentrations (C) were determined as a function of time by sampling from an indwelling venous cannula. The pharmacokinetic analysis of resultant C versus time data, together with that from an intravenous control experiment, is described to determine the amount absorbed as a function of time. Following aerosol administration according to the chosen respiratory regime, fluorescein was rapidly absorbed from the RT. The methodology will enable systematic variation of the particle size and positive-pressure respiratory regime in order to determine effects on drug absorption kinetics.

Absorption↗
PubMed2004

Perfluorocarbon species and nebulizer type influence aerosolization rate and particle size of perfluorocarbon aerosol.

PURPOSE: Aerosolization of perfluorocarbons (PFC) has been proven beneficial in vivo. The present in vitro study was performed to investigate, how PFC-aerosolization is affected by type of nebulizer and PFC properties. MATERIALS AND METHODS: Aerosolization rate was studied of 4 different PFC that were nebulized using 3 different jet nebulizers (operating at different flows: 4.1; 7.1; 13 l/min) and one ultrasonic nebulizer. Distribution of aerosol particle size was determined with a laser diffraction device. RESULTS: Between the studied nebulizers, considerable differences in the aerosolization rate were found. Aerosolization rate was significantly lower for PFOB (0.48-1.24 mL/min), when compared with PF 5080, RM 101 and FC 77 (1.33-4.75 mL/min). The ultrasonic nebulizer did not generate an aerosol but rather PFC vapor. Lowest mass median diameter (MMD) was found for PFOB and varied between the jet nebulizers from 2.2 and 3.7 microm, with a small range in particle size (maximum of 7.3 microm). FC 77 had highest MMD (3.5 to 9.2 microm) and greatest range of particle size of up to 13 microm. CONCLUSIONS: Our in vitro data show that aerosolization rate depends mainly on density of PFC and the flow of nebulizer. Particle size distribution is affected by PFC properties. Our result may explain controversial results of published in vivo studies.

Administration, Inhalation↗
PubMed2004

On-road exposure to highway aerosols. 1. Aerosol and gas measurements.

On-road experiments were conducted to determine the sensitivities of rats to real-world aerosol. This article summarizes the on-road aerosol and gas measurements and provides background information for the companion paper on the rat exposures. Measurements were carried out over 10 days, 6 h/day, driving a route from Rochester to Buffalo. Aerosol instrumentation used in this study included two scanning mobility particle sizers (SMPS) to determine the aerosol size distribution from 10 to 300 nm, 2 stand-alone condensation particle counters to determine the total aerosol number concentration, and an electrical aerosol detector to determine the aerosol length concentration. A thermal denuder (TD) was used with one of the SMPS instruments to determine the size distribution of the non-volatile fraction. Filter samples were collected and analyzed for elemental carbon, and gas analyzers measured ambient levels of CO, CO(2), and NO. Average daily total aerosol number concentration ranged from 200,000 to 560,000 particles/cm(3). Past studies on urban highways have measured total number concentrations ranging between 10(4) and 10(6) particles/cm(3). The average daily NO concentration ranged from 0.10 to 0.24 ppm and the corresponding CO(2) concentration ranged from 400 to 420 ppm. The average daily geometric number mean particle size determined by the SMPS ranged from 15 to 20 nm. The TD reduced the average SMPS number concentration between 87 and 95% and the SMPS volume between 54 and 83%, suggesting that most of the particles consisted of volatile material. The TD also increased the geometric number mean diameter from 15 to 20 nm to 30 to 40 nm.

Aerosols↗
PubMed2004

Aerosol ion characteristics during the Big Bend Regional Aerosol and Visibility Observational study.

The ionic compositions of particulate matter with aerodynamic diameter < or = 2.5 microm (PM2.5) and size-resolved aerosol particles were measured in Big Bend National Park, Texas, during the 1999 Big Bend Regional Aerosol and Visibility Observational study. The ionic composition of PM2.5 aerosol was dominated by sulfate (SO4(2-)) and ammonium (NH4+). Daily average SO4(2-) and NH4+ concentrations were strongly correlated (R2 = 0.94). The molar ratio of NH4+ to SO4(2-) averaged 1.54, consistent with concurrent measurements of aerosol acidity. The aerosol was observed to be comprised of a submicron fine mode consisting primarily of ammoniated SO4(2-) and a coarse particle mode containing nitrate (NO3-). The NO3- appears to be primarily associated with sea salt particles where chloride has been replaced by NO3-, although formation of calcium nitrate (Ca(NO3)2) is important, too, on several days. Size-resolved aerosol composition results reveal that a size cut in particulate matter with aerodynamic diameter < or = 1 microm would have provided a much better separation of fine and coarse aerosol modes than the standard PM2.5 size cut utilized for the study. Although considerable nitric acid exists in the gas phase at Big Bend, the aerosol is sufficiently acidic and temperatures sufficiently high that even significant future reductions in PM2.5 SO4(2-) are unlikely to be offset by formation of particulate ammonium nitrate in summer or fall.

Aerosols↗
PubMed1987

Development of a sampling and analytical method for measuring the epoxy content of aerosols: II. Application of the method to epoxy-containing aerosols.

Aerosols generated by epoxy spray painting consist of droplets containing partially-cured mixtures of epoxy resins and curing agents, as well as pigments, solvents and diluents. A sampling and analytical method has been developed to measure the epoxy content of these aerosols. The method collects the aerosol in a midget impinger containing dimethyl formamide, which inhibits the curing reaction between the epoxy and curing agent, preserving the unreacted epoxy functional groups present in the aerosol. The impinger contents are analyzed by reacting the epoxy with an excess of bromide generated in situ from tetraethylammonium bromide, and measuring the unreacted bromide in the reaction mixture by normal pulse polarography. The precision and accuracy of the method have been evaluated using a pure epoxy resin as a model compound. The method was applied to aerosols containing mixtures of epoxy resin and amine curing agents in various degrees of cure, to aerosols containing large quantities of nonepoxy compounds, and to aerosols of epoxy surface coatings. The method is capable of precise and accurate measurement of epoxide functionality, and it applicable to the measurement of epoxy-containing aerosols in spray finishing operations.

Aerosols↗
PubMed1996

Aerosol bolus dispersion and aerosol-derived airway morphometry: assessment of lung pathology and response to therapy, Part 1.

review discusses the potential utility of two methods using inhaled aerosols to detect and diagnose lung disease and to evaluate the efficacy of therapy. Aerosol bolus dispersion measures convective gas mixing; aerosol-derived airway morphometry assesses the calibers of airway and airspaces. These two methods are discussed in terms of their ease of use (simplicity and acceptability) and current data regarding their validity, reproducibility, specificity, sensitivity, and detection of lung improvement with therapy. Part 1 of this review focuses upon aerosol bolus dispersion; Part 2(1) focuses upon aerosol-derived airway morphometry. Aerosol bolus dispersion has many features that make it clinically attractive. It is simple to administer and patients can successfully perform the maneuvers. It detects known alterations in the lungs. It is reproducible and has high specificity and sensitivity. However, every lung disease or condition known to be detected by aerosol bolus dispersion is also detected by spirometery, maximal expiratory flow-volume curves, or another conventional lung function test. This, aerosol bolus dispersion appears best reserved as a specialized method to supplement conventional lung function tests and to characterize convective gas transport.

Aerosols↗
PubMed1997

Aerosol delivery of liposome-encapsulated ciprofloxacin: aerosol characterization and efficacy against Francisella tularensis infection in mice.

The aerosol delivery of liposome-encapsulated ciprofloxacin by using 12 commercially available jet nebulizers was evaluated in this study. Aerosol particles containing liposome-encapsulated ciprofloxacin generated by the nebulizers were analyzed with a laser aerodynamic particle sizer. Mean mass aerodynamic diameters (MMADs) and geometric standard deviations (GSDs) were determined, and the drug contents of the sampling filters from each run onto which aerosolized liposome-encapsulated ciprofloxacin had been deposited were analyzed spectrophotometrically. The aerosol particles of liposome-encapsulated ciprofloxacin generated by these nebulizers ranged from 1.94 to 3.5 microm, with GSDs ranging from 1.51 to 1.84 microm. The drug contents of the sampling filters exposed for 1 min to aerosolized liposome-encapsulated ciprofloxacin range from 12.7 to 40.5 microg/ml (0.06 to 0.2 mg/filter). By using the nebulizer selected on the basis of most desirable MMADs, particle counts, and drug deposition, aerosolized liposome-encapsulated ciprofloxacin was used for the treatment of mice infected with 10 times the 50% lethal dose of Francisella tularensis. All mice treated with aerosolized liposome-encapsulated ciprofloxacin survived the infection, while all ciprofloxacin-treated or untreated control mice succumbed to the infection (P < 0.001). These results suggest that aerosol delivery of liposome-encapsulated ciprofloxacin to the lower respiratory tract is feasible and that it may provide an effective therapy for the treatment of respiratory tract infections.

Administration, Inhalation↗
PubMed1994

Acute effect of sodium cromoglycate on airway narrowing induced by 4.5 percent saline aerosol. Outcome before and during treatment with aerosol corticosteroids in patients with asthma.

STUDY OBJECTIVE: To investigate the acute effect of sodium cromoglycate on airway responses to 4.5 percent saline aerosol challenge, before and during treatment with inhaled budesonide--a corticosteroid. DESIGN: Open study, with a total of five visits, two before budesonide treatment, and three follow-up visits, two between 5 and 6 weeks and one at more than 11 weeks. SETTING: Referral-based Respiratory Investigation Unit at Royal Prince Alfred Hospital, a major Sydney-based teaching hospital. PATIENTS: Eleven patients with asthma (ten atopic), with a PD20 FEV1 to 4.5 percent saline aerosol challenge and about to commence inhaled budesonide for treatment of their asthma. INTERVENTIONS: The 40 mg of sodium cromoglycate was inhaled before a 4.5 percent NaCl challenge, both before and after regular (36 +/- 9 d) treatment with budesonide (1,000 micrograms/d). The final challenge was repeated in ten subjects after 11 weeks or more of treatment with budesonide. MEASUREMENTS AND RESULTS: Sensitivity to 4.5 percent saline aerosol was measured as the dose of saline aerosol required to induce a 20 percent fall in FEV1 (PD20). Reactivity was measured as the dose-response slope by taking the percent fall in FEV1 and dividing it by the dose required to induce the fall. On the control day the geometric mean PD20 (95 percent CI) for 4.5 percent saline aerosol was 2.8 (1.4 to 5.4) and the dose response slope (DRS) 5.6 (2.9-11.1). An acute dose of sodium cromoglycate reduced sensitivity (PD20) by 8-fold and reactivity (DRS) 12.3-fold. This effect was similar in magnitude to that measured after regular treatment with budesonide alone. When sodium cromoglycate was given during treatment with budesonide, the PD20 was reduced 16-fold and the DRS 42-fold, and this was greater than the reduction with budesonide taken for 3 months (p < 0.03, p < 0.05 respectively). CONCLUSIONS: Sodium cromoglycate inhibits responses to 4.5 percent saline aerosol and has additional benefits to those conferred by aerosol steroids. The mechanism for responsiveness to saline aerosol and efficacy of these drugs may relate to alteration in chloride ion channel regulation by inflammation.

Adolescent↗