Clouds and “throat hit”: Effects of liquid composition on nicotine emissions and physical characteristics of electronic cigarette aerosols

Electronic cigarettes (ECIGs) heat and vaporize a liquid mixture to produce an inhalable aerosol that can deliver nicotine to the user. The liquid mixture is typically composed of propylene glycol (PG) and vegetable glycerin (VG), in which are dissolved trace quantities of flavorants and, usually, nicotine. Due to their different chemical and thermodynamic properties, the proportions of PG and VG in the liquid solution may affect nicotine delivery and user sensory experience. In social media and popular culture, greater PG fraction is associated with greater “throat-hit,” a sensation that has been attributed in cigarette smokers to increased presence of vapor-phase nicotine. VG, on the other hand, is associated with thicker and larger exhaled “clouds.” In this study, we aim to investigate how PG/VG ratio influences variables that relate to nicotine delivery and plume visibility. Aerosols from varying PG/VG liquids were generated using a digitally controlled vaping instrument and a commercially available ECIG, and analyzed for nicotine content by GC-MS. Particle mass and number distribution were determined using a six-stage cascade impactor and a fast particle spectrometer (TSI EEPS), with tightly controlled dilution and sampling biases. A Mie theory model was used to compute the aerosol scattering coefficients in the visible spectrum. Decreasing the PG/VG ratio resulted in a decrease in total particulate matter (TPM) and nicotine yield (R² > 0.9, p < .0001). Measured particle count median diameter ranged between 44 and 97nm, and was significantly smaller for PG liquids. Although the particle mass concentration was lower, aerosols produced using liquids that contained VG had an order of magnitude greater light scattering coefficients. These findings indicate that PG/VG ratio is a strong determinant of both nicotine delivery and user sensory experience.

Copyright © 2017 American Association for Aerosol Research     

Transport phenomena governing nicotine emissions from electronic cigarettes: Model formulation and experimental investigation

Electronic cigarettes (ECIGs) electrically heat and aerosolize a liquid-containing propylene glycol (PG), vegetable glycerin (VG), flavorants, water, and nicotine. ECIG effects and proposed methods to regulate them are controversial. One regulatory focal point involves nicotine emissions. We describe a mathematical model that predicts ECIG nicotine emissions. The model computes the vaporization rate of individual species by numerically solving the unsteady species and energy conservation equations. To validate model predictions, yields of nicotine, total particulate matter, PG, and VG were measured while manipulating puff topography, electrical power, and liquid composition across 100 conditions. Nicotine flux, the rate at which nicotine is emitted per unit time, was the primary outcome. Across conditions, the measured and computed nicotine flux were highly correlated (r = 0.85, p < .0001). As predicted, device power, nicotine concentration, PG/VG ratio, and puff duration influenced nicotine flux (p < .05), while water content and puff velocity did not. Additional empirical investigation revealed that PG/VG liquids act as ideal solutions, that liquid vaporization accounts for more than 95% of ECIG aerosol mass emissions, and that as device power increases the aerosol composition shifts towards the less volatile components of the parent liquid. To the extent that ECIG regulations focus on nicotine emissions, mathematical models like this one can be used to predict ECIG nicotine emissions and to test the effects of proposed regulation of factors that influence nicotine flux.

Copyright © 2017 American Association for Aerosol Research     

Prototype e-cigarette and the capillary aerosol generator (CAG) comparison and qualification for use in subchronic inhalation exposure testing

Our objective was to evaluate the suitability of using a capillary aerosol generator (CAG) instead of using e-cigarette devices in 90-day or longer inhalation studies. Aerosol characteristics for both the CAG (which uses heat to produce a condensation aerosol) and e-cigarette generators have been previously reported, but a side-by-side comparison with the identical formulation has not been reported. Aerosols from both devices were analyzed immediately after generation for chemicals in the formulation (propylene glycol [PG], glycerin, water, and nicotine), selected carbonyls (acetaldehyde, acrolein, and formaldehyde) by ultra-performance liquid chromatography with ultraviolet detection (UPLC-UV), and a chemical fingerprint analysis using gas chromatography-mass spectroscopy (GC-MS). Aerosol capture methods for chemical analysis included Cambridge filter pads or two impingers in series each containing solution to trap and stabilize selected carbonyl compounds. Particle size distribution (cascade impactor) and exposure port uniformity (gravimetric) was measured in four rodent inhalation exposure chambers under inhalation study conditions. The aerosol of both generators contained the same known and unknown chemicals. Similar levels of compounds in the formula except for PG were detected in the aerosol of both generators. CAG produced more consistent particulate aerosol than e-cigarette generator and had lower levels of carbonyls primarily due to lower levels of formaldehyde. Exposure port concentrations were consistent and closer to target values with the CAG compared to the e-cigarette aerosol generator. CAG was easier to operate on a daily basis although more difficult to maintain because it required daily cleaning compared to single-use e-cigarettes. CAG was determined to be suitable for use in 90-day or longer inhalation studies.

Copyright © 2016 American Association for Aerosol Research     

Electronic cigarette-generated aldehydes: The contribution of e-liquid components to their formation and the use of urinary aldehyde metabolites as biomarkers of exposure

Electronic cigarettes (e-cigarette) have emerged as a popular electronic nicotine delivery system (ENDS) in the last decade. Despite the absence of combustion products and toxins such as carbon monoxide (CO) and tobacco-specific nitrosamines (TSNA), carbonyls including short-chain, toxic aldehydes have been detected in e-cigarette-derived aerosols up to levels found in tobacco smoke. Given the health concerns regarding exposures to toxic aldehydes, understanding both aldehyde generation in e-cigarette and e-cigarette exposure is critical. Thus, we measured aldehydes generated in aerosols derived from propylene glycol (PG): vegetable glycerin (VG) mixtures and from commercial e-liquids with flavorants using a state-of-the-art carbonyl trap and mass spectrometry. To track e-cigarette exposure in mice, we measured urinary metabolites of 4 aldehydes using ULPC-MS/MS or GC-MS. Aldehyde levels, regardless of abundance (saturated: formaldehyde, acetaldehyde???unsaturated: acrolein, crotonaldehyde), were dependent on the PG:VG ratio and the presence of flavorants. The metabolites of 3 aldehydes – formate, acetate, and 3-hydroxypropyl mercapturic acid (3-HPMA; acrolein metabolite) – were increased in urine after e-cigarette aerosol and mainstream cigarette smoke (MCS) exposures, but the crotonaldehyde metabolite (3-hydroxy-1-methylpropylmercapturic acid, HPMMA) was increased only after MCS exposure. Interestingly, exposure to menthol-flavored e-cigarette aerosol increased the levels of urinary 3-HPMA and sum of nicotine exposure (nicotine, cotinine, trans-3′-hydroxycotinine) relative to exposure to a Classic Tobacco-flavored e-cigarette aerosol. Comparing these findings with aerosols of other ENDS and by measuring aldehyde-derived metabolites in human urine following exposure to e-cigarette aerosols will further our understanding of the relationship between ENDS use, aldehyde exposure, and health risk.

© 2018 American Association for Aerosol Research     

Differential diffusion analyzer

In this article, a proof of concept of a new measurement instrument, differential diffusion analyzer (DDA), is established. The DDA enables the measurement of the size distribution of sub-10 nm aerosol particles, and it can also be used as a size classifier to separate a certain particle size from a size distribution for subsequent analysis. The developed technique is based on the diffusion separation of different size particles. Thus, the main advantage of the DDA compared to other methods is that particle charging is not required. Simulated and experimentally measured transmission efficiencies show that the diffusion-based differential size classification is a feasible concept, and moreover, shows that particle size is inversely proportional to the square root of the total flow rate.

Copyright © 2017 American Association for Aerosol Research     

Preliminary investigation of a water-based method for fast integrating mobility spectrometry

A water-based condensational growth channel was developed for imaging mobility-separated particles within a parallel plate separation channel of the Fast Integrated Mobility Spectrometer (FIMS). Reported are initial tests of that system, in which the alcohol condenser of the FIMS was replaced by a water-based condensational growth channel. Tests with monodispersed sodium chloride aerosol verify that the water-condensational growth maintained the laminar flow, while providing sufficient growth for particle imaging. Particle positions mapped onto particle mobility, in accordance with theoretical expectations. Particles ranging in size from 12 nm to 100 nm were counted with the same efficiency as with a butanol-based ultrafine particle counter, once inlet and line losses were taken into account.

Copyright © 2017 American Association for Aerosol Research     

Performance of ventilation filtration technologies on characteristic traffic related aerosol down to nanocluster size

Near traffic routes and urban areas, the outdoor air particle number concentration is typically dominated by ultrafine particles. These particles can enter into the nearby buildings affecting the human exposure on ultrafine particles indoors. In this study, we demonstrate an aerosol generation system which mimics the characteristic traffic related aerosol. The aerosol generation system was used to determine the size-resolved particle filtration efficiencies of five typical commercial filters in the particle diameter range of 1.3–240 nm. Two different HEPA filters were observed to be efficient in all particle sizes. A fibrous filter (F7) was efficient at small particle sizes representing the nucleation mode of traffic related aerosol, but its efficiency decreased down to 60% with the increasing particle size. In contrast, the filtration efficiency of an electrostatic precipitator (ESP) increased as a function of the particle size, being more efficient for the soot mode of traffic related aerosol than for the nucleation mode. An electret filter with a charger was relatively efficient (filtration efficiency >85%) at all the observed particle sizes. The HEPA, F7 and electret filters were found to practically remove the particles/nanoclusters smaller than 3 nm. All in all, the filtration efficiencies were observed to be strongly dependent on the particle size and significant differences were found between different filters. Based on these results, we suggest that the particulate filter test standards should be extended to cover the ultrafine particles, which dominate the particle concentrations in outdoor air and are hazardous for public health.

Copyright © 2017 American Association for Aerosol Research     

Unique DNA-barcoded aerosol test particles for studying aerosol transport

Data are presented for the first use of novel DNA-barcoded aerosol test particles that have been developed to track the fate of airborne contaminants in populated environments. Until DNATrax (DNA Tagged Reagents for Aerosol eXperiments) particles were developed, there was no way to rapidly validate air transport models with realistic particles in the respirable range of 1–10 μm in diameter. The DNATrax particles, developed at Lawrence Livermore National Laboratory (LLNL) and tested with the assistance of the Pentagon Force Protection Agency, are the first safe and effective materials for aerosol transport studies that are identified by DNA molecules. The use of unique synthetic DNA barcodes overcomes the challenges of discerning the test material from pre-existing environmental or background contaminants (either naturally occurring or previously released). The DNATrax particle properties are demonstrated to have appropriate size range (approximately 1–4.5 μm in diameter) to accurately simulate bacterial spore transport. Here, we describe details of the first field test of the DNATrax aerosol test particles in a large indoor facility.

Copyright © 2016 American Association for Aerosol Research     

Assessment of a Cylindrical and a Rectangular Plate Differential Mobility Analyzer for Size Fractionation of Nanoparticles at High-Aerosol Flow Rates

An existing differential mobility analyzer (DMA) of cylindrical electrodes and a novel DMA of rectangular plate electrodes are demonstrated for size fractionation of nanoparticles at high-aerosol flow rates in this work. The two DMAs are capable of delivering monodisperse size selected nanoparticles (SMPS σ_g < 1.1) at gas flow rates ranging from 200 slm to 500 slm. At an aerosol flow rate of 200 slm, the maximum attainable particle mean size is of about 20 nm for the cylindrical DMA and of nearly 50 nm for the rectangular plate DMA. The number concentration of the monodisperse nanoparticles delivered by the high-flow DMAs spans from 10⁴ cm^?3 to 10⁶ cm^?3 depending upon the particle mean size and particle size dispersion.

Copyright 2014 American Association for Aerosol Research     

Design and evaluation of an aerodynamic focusing micro-well aerosol collector

Aerosol sampling and identification is vital for the assessment and control of particulate matter pollution, airborne pathogens, allergens, and toxins and their effect on air quality, human health, and climate change. In situ analysis of chemical and biological airborne components of aerosols on a conventional filter is challenging due to dilute samples in a large collection region. We present the design and evaluation of a micro-well (µ-well) aerosol collector for the assessment of airborne particulate matter (PM) in the 0.5–3 µm size range. The design minimizes particle collection areas allowing for in situ optical analysis and provides an increased limit of detection for liquid-based assays due to the high concentrations of analytes in the elution/analysis volume. The design of the collector is guided by computational fluid dynamics (CFD) modeling; it combines an aerodynamic concentrator inlet that focuses the aspirated aerosol into a narrow beam and a µ-well collector that limits the particle collection area to the µ-well volume. The optimization of the collector geometry and the operational conditions result in high concentrations of collected PM in the submillimeter region inside the µ-well. Collection efficiency experiments are performed in the aerosol chamber using fluorescent polystyrene microspheres to determine the performance of the collector as a function of particle size and sampling flow rate. The collector has the maximum collection efficiency of about 75% for 1 µm particles for the flow rate of 1 slpm. Particles bigger than 1 µm have lower collection efficiencies because of particle bounce and particle loss in the aerodynamic focusing inlet. Collected samples can be eluted from the device using standard pipettes, with an elution volume of 10–20 µL. The transparent collection substrate and the distinct collection region, independent of particle size, allows for in situ optical analysis of the collected PM.

© 2017 American Association for Aerosol Research     

Assessing the accuracy of complex refractive index retrievals from single aerosol particle cavity ring-down spectroscopy

Cavity ring-down spectroscopy (CRDS) of single, optically manipulated aerosol particles affords quantitative retrieval of refractive indices for particles of fixed or evolving composition with high precision. Here, we quantify the accuracy with which refractive index determinations can be made by CRDS for single particles confined within the core of a Bessel laser beam and how that accuracy is degraded as the particle size is progressively reduced from the coarse mode (>1 μm radius) to the accumulation mode (<500 nm radius) regime. We apply generalized Lorenz–Mie theory to the intra-cavity standing wave to explore the effect of particle absorption on the distribution of extinction cross section determinations resulting from stochastic particle motion in the Bessel beam trap. The analysis provides an assessment of the accuracy with which the real, n, and imaginary, κ, components of the refractive index can be determined for a single aerosol particle.

Published with license by American Association for Aerosol Research     

Modification and laboratory evaluation of a TSI ultrafine condensation particle counter (Model 3776) for airborne measurements

A butanol-type ultrafine condensation particle counter (UCPC, Model 3776, TSI, Inc., Shoreview, MN, USA), which can achieve a 50% detection efficiency diameter (d₅₀) of 2.5 nm using a capillary-sheath structure, was modified and tested in the laboratory for airborne measurements. The aerosol flow rate through the capillary is a key factor affecting the quantification of aerosol particle number concentrations. A pressure-dependent correction factor for the aerosol flow rate was determined using a newly added mass flow meter for the sheath flow and the external calibration system. The effect of particle coincidence in the optical sensing volume was evaluated using an aerosol electrometer (AE, Model 3068B, TSI, Inc.) as a reference. An additional correction factor for the coincidence effect was derived to improve the quantification accuracy at higher concentrations. The particle detection efficiency relative to the AE was measured for mobility diameters of 3.1–50 nm and inlet absolute pressures of 101–40 kPa. The pressure dependence of the d₅₀ value, asymptotic detection efficiency, and shape of the particle detection efficiency curve is discussed, along with simple theoretical calculations for the diffusion loss of particles and the butanol saturation ratio in the condenser.

© 2017 American Association for Aerosol Science     

A New Clean Air Delivery Rate Test Applied to Five Portable Indoor Air Cleaners

Air pollution has been recognised as one of the major risk factors for the global burden of disease. In modern society the majority of the exposure occurs indoors where people spend most of their time. Indoor air quality may be improved with portable air cleaners utilizing various cleaning techniques, such as filtration, electrostatic precipitation, and ionization. The objective of this study was to quantify air cleaner particle removal by particle size resolved clean air delivery rates (CADR). This was obtained by utilizing particle concentration measurements and indoor aerosol modeling. Our test protocol was applied to five air cleaners designed for household and office use. For particles with diameters above 100 nm and at the chosen settings, the CADR was around 40 m³/h for an ion generator, around 70 m³/h for an electrostatic precipitator, and ranging from 100 to almost 300 m³/h for the three filter-based air cleaners. Similar performances were obtained for ultrafine particles, except for the ion generator that performed better in this size range.

Copyright 2014 American Association for Aerosol Research     

Application of centrifugal filter to aerosol size distribution measurement

In the present work, the centrifugal filter proposed by the authors was applied to classify aerosol particles followed by the detection of total mass or number concentrations so as to measure the size distribution of aerosol particles. The structure and operating condition of the centrifugal filter were optimized in order to attain sharp separation curves with various cut-off sizes between 0.3 and 10 μm. The aerosol penetrating the centrifugal filter at various rotation speeds was measured with a photometer to determine the total mass concentration. The virtue of this system is that the cut-off size is varied just by scanning the rotation speed of filter and that it can be applied to the measurement of high concentration aerosols without dilution by choosing an appropriate filter medium. As a result, the centrifugal filter was successfully applied to measure the size distribution of solid particles in size ranging from 0.3 to 10 μm.

Copyright © 2017 American Association for Aerosol Research     

Spatial aerosol flow maldistribution: A design flaw confounding the proper calibration and data interpretation of stages “0” and “1” of the Andersen eight-stage nonviable cascade impactor

We introduced monodisperse calibrant particles into an eight-stage non-viable Andersen cascade impactor (ACI) operated at 28.3 L/min and separately quantified the particle mass captured under each of the four concentric rings of nozzles on stages 0 and 1, the entry and succeeding stages of this impactor. On both stages, we found that each ring of nozzles has a particle capture efficiency behavior that differs from the others, and the fraction of calibrant particles deposited under each of the individual rings of nozzles depended on the particle size. We believe this behavior derives primarily from a radial flow velocity non-uniformity associated with recirculation zones introduced by the 110° expansion angle of the inlet cone. Because of these recirculation zones, the inertia of particles larger than about 5 µm aerodynamic diameter will cause their point-wise local concentration to differ from the concentration at the inlet entry. This concentration maldistribution continues to stage 1 primarily because of the annular collection plate at stage 0. The influence of the inlet cone aerodynamics on the performance of both stages means that the size of particles deposited on these plates will be uncertain unless the aerosol transport entering the impactor associated with calibration using monodisperse particles exactly simulates the in-use aerosol flow conditions. The degree of realism necessary in the calibration method has heretofore not been discussed in published calibrations of the ACI, introducing uncertainty in the size interpretation of the particle mass collected on stages 0 and 1 in practical applications of this impactor.

Copyright © 2017 American Association for Aerosol Research     

Single Particle Measurements of the Optical Properties of Small Ice Crystals and Heterogeneous Ice Nuclei

Dust aerosol and ice crystals are two major types of nonspherical particles in the atmosphere which have significant roles in cloud-aerosol interactions and the radiative budget. The presence of dust and ice often coincide in the atmosphere because dust particles are efficient ice nuclei. The size and composition dependence of the scattering properties of dust and ice are needed to assess their individual contributions to the optical scattering of sunlight. Here we present a new measurement technique used to determine the single particle forward scattering, backscattering, and depolarization ratio (at a wavelength of 680 nm) for representative nonspherical atmospheric particles. The Texas A&M University Continuous Flow Diffusion Chamber (CFDC) was used as an ice crystal generator to produce ice crystals via both homogenous and heterogeneous nucleation mechanisms under well-controlled laboratory conditions. Optical scattering properties of mineral dusts and small ice crystals (0.6 μm to 50 μm optical diameter) were measured by the Droplet Measurement Technologies, Inc. (DMT) Cloud Aerosol Spectrometer with Polarization (CASPOL). Significant differences between the optical properties of single dusts and ice particles of the same size were observed. Differences between the optical signatures of homogeneously and heterogeneously nucleated ice crystals were not statistically significant. Our results suggest that atmospheric ice crystals can be identified and quantified independently from the dust particles on which they form based on analysis of their backscatter and depolarization signals.

Copyright 2014 American Association for Aerosol Research     

Molecular-resolution simulations of new particle formation: Evaluation of common assumptions made in describing nucleation in aerosol dynamics models

Aerosol dynamics models that describe the evolution of a particle distribution incorporate nucleation as a particle formation rate at a small size around a few nanometers in diameter. This rate is commonly obtained from molecular models that cover the distribution below the given formation size – although in reality the distribution of nanometer-sized particles cannot be unambiguously divided into separate sections of particle formation and growth. When incorporating nucleation, the distribution below the formation size is omitted, and the formation rate is assumed to be in a steady state. In addition, to reduce the modeled size range, the formation rate is often scaled to a larger size based on estimated growth and scavenging rates and the assumption that also the larger size is in a steady state. This work evaluates these assumptions by simulating sub-10 nm particle distributions in typical atmospheric conditions with an explicit molecular-resolution model. Particle formation is included either (1) dynamically, that is, the whole size range starting from single vapor molecules is modeled explicitly or (2) implicitly by using an input formation rate as is done in aerosol models. The results suggest that while each assumption can affect the outcome of new particle formation modeling, the most significant source of uncertainty affecting the formation rates and resulting nanoparticle concentrations is the steady-state assumption, which may lead to an overprediction of the concentrations by factors of approximately from two to even orders of magnitude. This can have implications for modeling and predicting atmospheric particle formation.

Copyright © 2017 American Association for Aerosol Research     

Estimation of acoustic forces on submicron aerosol particles in a standing wave field

The net acoustic force acting on submicron particles suspended in a gas and exposed to a standing wave field is investigated as a function of particle size, by measuring both the aerosol number density and size distribution in a flow-through resonator. By taking into account all contributions relevant to the net force, this experimental study provides a first estimate for the acoustic radiation force in a size range where molecular effects are expected to be significant. The experiment consists of an electrostatic transducer generating a standing wave in the 50–80 kHz frequency range, with the submicron aerosol particles concentrated at pressure antinodes located across the height of a rectangular channel. A section of the flow is sampled isokinetically and analyzed using a Scanning Mobility Particle Sizer (SMPS), while the nodal patterns are visualized simultaneously using light scattering. The net acoustic force is calculated from their measured displacement along the axis of the 1D standing wave field. The component of this force resulting from radiation pressure is estimated by subtracting contributions from other forces. The results provide the first experimental estimation of the size dependence of the acoustic contrast factor for submicron aerosol particles, demonstrating the possibility of performing acoustic separation for diameters as small as 150 nm.

Copyright © 2018 American Association for Aerosol Research     

Mobility particle size spectrometers: Calibration procedures and measurement uncertainties

Mobility particle size spectrometers (MPSS) belong to the essential instruments in aerosol science that determine the particle number size distribution (PNSD) in the submicrometer size range. Following calibration procedures and target uncertainties against standards and reference instruments are suggested for a complete MPSS quality assurance program: (a) calibration of the CPC counting efficiency curve (within 5% for the plateau counting efficiency; within 1 nm for the 50% detection efficiency diameter), (b) sizing calibration of the MPSS, using a certified polystyrene latex (PSL) particle size standard at 203 nm (within 3%), (c) intercomparison of the PNSD of the MPSS (within 10% and 20% of the dN/dlogDP concentration for the particle size range 20–200 and 200–800 nm, respectively), and (d) intercomparison of the integral PNC of the MPSS (within 10%). Furthermore, following measurement uncertainties have been investigated: (a) PSL particle size standards in the range from 100 to 500 nm match within 1% after sizing calibration at 203 nm. (b) Bipolar diffusion chargers based on the radioactive nuclides Kr⁸⁵, Am²⁴¹, and Ni⁶³ and a new ionizer based on corona discharge follow the recommended bipolar charge distribution, while soft X-ray-based charges may alter faster than expected. (c) The use of a positive high voltage supply show a 10% better performance than a negative one. (d) The intercomparison of the integral PNC of an MPSS against the total number concentration is still within the target uncertainty at an ambient pressure of approximately 500 hPa.

Copyright © 2018 Published with license by American Association for Aerosol Research     

Mathematical modeling and numerical simulation of surfactant delivery within a physical model of the neonatal trachea for different aerosol characteristics

Surfactant aerosol delivery in conjunction with a noninvasive respiratory support holds the potential to treat neonatal respiratory distress syndrome in a safe manner. The objective of the present study was to gain knowledge in order to optimize the geometry of an intracorporeal inhalation catheter and improve surfactant aerosol delivery effectiveness in neonates. Initially, a mathematical model capable of predicting the aerosol flow generated by this inhalation catheter within a physical model of the neonatal trachea was implemented and validated. Subsequently, a numerical study was performed to analyze the effect of the aerosol liquid droplet size and mass flow rate on surfactant delivery and on the required aerosolization time period. Experimental validation of the mathematical model showed a close prediction of the air axial velocity at the distal end of the physical model, with an absolute error between 0.01 and 0.15 m/s. Furthermore, an admissible absolute error between 0.2 and 2 µm was attained in the prediction of the aerosol mean aerodynamic diameter and mass median aerodynamic diameter in this region. The numerical study highlighted the beneficial effects of generating an intracorporeal aerosol with a mass median aerodynamic diameter higher than 4 µm and a surfactant mass flow rate above 8.93 mg/s in order to obtain effective surfactant delivery in neonates with minimal airway manipulation.

Copyright © 2017 American Association for Aerosol Research