Albert Podgórski

Hydrodynamical model of pulmonary clearance

The theoretical description of the behaviour of a thin liquid film covered with a monomolecular surfactant layer is presented. This film is subjected to oscillatory compressions and tensions. It follows from the solution of this model that a net outflow of liquid from the film takes place. The size of this outflow has been estimated for variable parameters of the model. The optimum value of the displacement as a function of the Ma/Re Sc factor has been found. The model was adapted to the phenomenon of alveoli clearance.

Penetration of Monodisperse, Singly Charged Nanoparticles through Polydisperse Fibrous Filters

The article presents experimental results and theoretical analysis of aerosol nanoparticle penetration through fibrous filters with a broad fiber diameter distribution. Four fibrous filters were produced using the melt-blown technique. The analysis of the filters’ SEM images indicated that they had log-normal fiber diameter distribution. Five kinds of proteins and two types of silica particles were generated by electrospraying and were then classified using a Parallel Differential Mobility Analyzer to obtain well-defined, monodisperse, singly charged challenge aerosols with diameters ranging from 6.3 to 27.2 nm. Particle penetration through the filters was determined using a water-based CPC. Experimental results were compared first with predictions derived from the classical theory of aerosol filtration. It is demonstrated that it is inappropriate to apply it to the arithmetic mean fiber diameter, as this results in turn in a huge underestimation of nanoparticle penetration. A better, but still unsatisfactory agreement is observed when that theory was used together with the pressure drop equivalent fiber diameter or when the Kirsch model of nonuniform fibrous media was applied. We show that the classical theory applied to any fixed fiber diameter predicts a stronger dependence of nanoparticle penetration on the Peclet number as compared to experimental data. All these observations were successfully explained by using our original partially segregated flow model that accounts for the filter fiber diameter distribution. It was found that the parameter of aerosol segregation intensity inside inhomogeneous filters increases with the increase in particle size, when the convective transport becomes more pronounced in comparison to the diffusive one.

Perfluorocarbon compound aerosols for delivery to the lung as potential 19F magnetic resonance reporters of regional pulmonary pO2.

RATIONALE AND OBJECTIVES Perfluorocarbon (PFC) aerosols present the opportunity for simultaneous analysis of lung structure and pulmonary oxygenation patterns. The authors investigated techniques to nebulize neat liquid PFCs for inhalation as a new method of PFC administration and tested the hypothesis that PFC aerosols may be developed for efficient delivery to the lung in an experimental rat model allowing the potential for sequential monitoring of pulmonary status via quantitative fluorine-19 (19F) magnetic resonance (MR) partial pressure of oxygen (pO2) imaging. METHODS Pneumatic aerosol generators were configured to produce a neat liquid PFC perfluorotributylamine (FC-43) aerosol. Perfluorocarbon inhalation breathing protocols for the rat model included: spontaneous direct breathing from an aerosol chamber, and use of a tracheotomy tube to bypass nasal breathing. The PFC aerosol delivery into the rat lung was documented through 19F MR imaging in correlation with high-resolution anatomic proton MR images. Theoretical model calculations for PFC mass deposition were compared with experimental results. RESULTS The pneumatic generator produced a PFC aerosol droplet within the theoretically targeted range (geometric mean particle diameter of 1.2 microns; concentration of approximately 4 x 10(7) droplets per cm3). No measurable aerosol reached the lungs during spontaneous breathing because of the efficient filtering capabilities of the turbinated nasal passages. With tracheotomy, aerosol depositions within the lung were achieved in mass quantities consistent with theoretical expectations; however, the distribution patterns were nonuniform and unpredictable. Oxygen-enhanced 19F imaging was demonstrated. CONCLUSIONS Perfluorocarbon aerosols of controlled size distribution can be produced at sufficient concentration with pneumatic generators for distribution to the terminal pulmonary architecture and visualization using 19F MR imaging. The potential exists for in vivo oxygen-sensitive imaging in the pulmonary system and development of sophisticated experimental animal models of systemic oxygen transport as a function of pulmonary status.

Deactivation of the Pulmonary Surfactant Dynamics by Toxic Aerosols and Gases

Interactions between selected toxic aerosols and gases occurring in the air at the workplace and the pulmonary surfactant (PS) have been studied with two physicochemical techniques in vitro. The Pulsating Bubble Surfactometer (PBS) and the Langmuir-Wilhelmy Balance (LWB) have been used for measurements of dynamic interfacial properties of the PS material after its contact with several gases (sulfur dioxide, nitrogen oxides, ozone, ammonia) and liquids (sulfuric, nitric and hydrochloric acids and ammonium hydroxide), which can be brought into the alveoli with the inhaled air. Surface tension-area relationships for the interface oscillations have been analyzed using qualitative criteria of normalized hysteresis area (HA(N)) and minimum surface tension (sigma(min)). It was demonstrated that, for each analyzed compound, inactivation of the surfactant occurs, but the critical concentrations and doses are compound specific, which suggests the toxic potential of the investigated substances with respect to PS. Possible mechanisms of the interactions between the investigated substances and the surfactant components are discussed. Degradation of the PS dynamical interfacial properties (HA(N) and sigma(min)), important from the physiological viewpoint, observed in our in vitro experiments, suggests a possibility of adverse health effect in the case of a chronic inhalation of toxic gases and aerosols, even at low concentration or after a short exposure to strongly contaminated air. It results in a slowdown of the pulmonary clearance rate and increase of the lung burden for both considered cases.

Flexible fibrous particle behaviour in the carrier gas flow around cylindrical obstacle

Abstract An equation of motion of a deformable fibrous particle accounting for the effects of inertia and gravity on its trajectory is presented. It is shown how the initial shape, orientation and slenderness of the particle as well as the transporting gas velocity affect the particle behaviour. The introductory results demonstrate that after an initial disturbance and change in shape the particle quickly accommodates to the flow along the gas streamlines. The deposition efficiency of such particles is smaller than that of rigid fibrous or spherical ones with the same mass.

Experimental study on fibrous particle deposition in the human nasal cast

Abstract The main purpose of this paper is an experimental study of a glass fiber deposition in a nasal cast. The geometrical structure of the cast chamber corresponded to the actual shape of a head airways. A three-dimensional tomographic picture of the head airways of a healthy human adult was used as the basis for preparing the cast. The cast consisted of two longitudinal sections what make possible the observation of the deposits after particular experiments. The total and regional—for four defined regions—deposition of fibers with diameter 0.8μm and aspect ratio β=10, 20 and 40 was measured. Using an image memory system analysis the characteristic orientation of deposits at particular region of the cast was determined.

Assessment of the Pulmonary Toxicity of Inhaled Gases and Particles With Physicochemical Methods

Physicochemical techniques used for evaluating the pulmonary surfactant (PS) quality are discussed as methods useful in assessing toxicity of inhaled gases and particles. Two standard devices, Langmuir-Wilhelmy film balance and pulsating bubble apparatus, are presented in detail, and the measured results of interaction between sulfuric acid and 2 models of PS materials are analyzed. The evident decrease in surface activity of the pulmonary surfactant after its contact with the acid at concentrations approaching 0.001 M may be considered as an indicator of the adverse effect, which can result in several health problems. The presented approach can be used as a method of assessing pulmonary toxicity of any substances present in the breathing air.

Novel Formulae for Deposition Efficiency of Electrically Neutral, Submicron Aerosol Particles in Bipolarly Charged Fibrous Filters Derived Using Brownian Dynamics Approach

Brownian dynamics (BD) method was employed to calculate the single fiber deposition efficiencies of electrically neutral, submicron aerosol particles in bipolarly charged and non-charged fibrous filters. It was found that a considerable increase in the deposition efficiency can be achieved by increasing the fiber charge density and that it is accompanied by a noticeable shift of the most penetrating particles size towards smaller particles. The results of the BD simulations obtained for various fiber charge densities and various particle diameters allowed us to derive new formulae relating a gain in the deposition efficiency due to action of the electrostatic force to the dimensionless polarization parameter, N σ 0 . These equations are applicable in much wider range of N σ 0 than other correlations available in the literature. A simple approximate rule for recalculating the form of the proposed formulae for another filter packing density was also presented. Theoretically predicted values of the deposition efficiency in bipolar electret filters were compared with our own experimental data as well as with the data available in the literature and a satisfactory agreement, better than in the case of other existing correlations, was obtained.

Optimized response characteristics of an optical particle spectrometer for size measurement of aerosols

Abstract The accuracy of aerosol particle size measurement based on light scattering from single particles depends strongly on the scattering angular range and particle refractive index. The particle size determination suffers frequently from multi-valuedness. Based on the Mie theory of light scattering, light collection angles allowing single-valued aerosol measurement were identified and utilized to design a new optical system with dual light scattering angular ranges. The light collecting optics is located co-axially in the forward (10–30°) and backward (150–170°) direction with reference to the illumination beam and allows a simultaneous measurement of both scattered light fluxes. We found that a weighted superposition of these light fluxes results in monotonically increasing response characteristics versus particle size. In this contribution we analyze the performance of the dual optical system in the particle size range from 0.1 up to 10 μm in diameter and show its capability for an accurate particle sizing and an assessment of the complex refractive index of aerosols.

Deposition and retention of ultrafine aerosol particles in the human respiratory system. Normal and pathological cases.

The particle number concentration in ambient air is dominated by nanometersized particles. Recent epidemiological studies report an association between the presence of nanoparticles in inhaled air at the workplace and acute morbidity and even mortality in the elderly. A theoretical model of deposition of 20 nm particles in the human alveolus was formulated. Gas flow structure and deposition rate were calculated for alveoli with different elastic properties of lung tissue. Data obtained in the paper show increased convective effects and diffusional rate of deposition of nanoparticles for alveoli with higher stiffness of the alveolar wall. The retention of deposited particles is also higher in these pathological alveoli. Results of our calculations indicate a possibility of existence of a positive loop of coupling in deposition and retention of nanoparticles in the lung with pathological changes.