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29.P.07 The effect of blocked bronchial airways on particle deposition patterns within airway bifurcations
J. Aerosol Sci.. Vol. 25, Suppl. I, pp. $483-$484, 1994
Copyright(~1994 Elsevier Science Ltd
Pergamon
29
P
07
Prin,~e~'~,, O~,.r,,a,n. A,, r,~h,. . . . . ~, 0021-8502/94 $7.00 + 0.00
THE EFFECT OF BLOCKED BRONCHIAL AIRWAYS ON PARTICLE DEPOSITION PA'VI'ERNS WITHIN AIRWAY BIFURCATIONS
I. B A L ~ S ~ Y
AND W. HOFMANN
Institut for Physik und Biophysik, Universitat Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria
KEYWORDS
Airway Bifurcation; Particle Deposition; Airway Blockage INTRODUCTION
Experimental observations and theoretical predictions have revealed local inhomogeneities of particle deposition within bronchial bifurcation models (BaltsMzy and Hofinann, 1993; Gradon and Orlicki, 1990; Kim and Iglesias, 1989; Martonen and Hofmann, 1986). Even in a symmetrically dividing bifurcation, partial constriction or total blockage of one of the daughter airways can produce significant asymmetric flow divisions. As a result, local deposition patterns in a diseased lung may be quite different from those in a healthy lung. Such a difference in localized particle deposition has important implications for aerosol therapy and risk assessment. METHODS
The present simulations of particle deposition patterns within bronchial airway bifurcations are based on our recently developed numerical model for the calculation of air velocity fields and aerosol particle trajectories in a three-dimensional bifurcation model (Bal~hgzy and Hofinann, 1993). In this numerical model, airflow is computed by solving the Navier-Stokes equations with a finite difference technique. Trajectories of aerosol particles within the bifurcation are then simulated by considering the simultaneous effects of inertial impaction, gravitational settling, Brownian motion, and interception, utilizing Monte Carlo methods. The geometry of the bronchial bifurcation model corresponds to the dimensions specifically employed in the Kim and Inglesias (1989) experiments, which are similar to the generation 3-4 juncture in Weibel's (1963) Model A. The inspiratory flow rate in the parent airway, Q,~, of 8 L min-1 is equivalent to a respiratory minute volumen of 32 L min-1, which is characterish~ of light activity breathing conditions. Consequently, a parabolic inlet flow profile has been adopted in the parent branch. RESULTS
Consistent with the experimental procedure of Kim and Iglesias (1989), the ratio of the flow rate in daughter airway A, QdA, to that in daughter airway B, QdB, adopts values of I (normal conditions), 2, 3 and 10 (partially blocked airway B), and infinity (totally blocked airway B). Our theoretical predictions of deposition efficiencies agree favorably with the experimentally reported data. For the sake of brevity, however, only the simulations for the totally blocked case will be presented here. The trajectories of 10 and 0.01 pm unit density particles, together with their starting points, are shown in Fig. 1 for the case that daughter airway B is totally blocked. These two particle sizes were selected here to illustrate the separate effects of the impact'i0n and sedimentation (dD = 10 pal) and diffusion (dv = 0.01 pm) mechanisms on the motion of inspired aerosols. The locatitns of the particles at the en'd of each time step are marked by dots; thus the number of steps illustrates their total flight times. AS 25 S.I-GG
$483
$484
1. BAL/~SHAZY and W. HOFMANN
For both particle sizes, only ,,5 dp = 10 prn Daughter - . ~ dp =0.01 pm Daughfer-A one particle is able to exit the bifurcation, while the remai, ~ ning particles deposit on the bifurcation walls. The corresponding deposition patterns for 1000 trajectories Y [i. . . . . are displayed in Fig. 2. Inhalation of 10 tun particles produces an intense hot spot at the carinal ridge. In addition, Daughter- B a second region of enhanced deposition can be obsc=rved at a given depth in daughter airway B. On the other hand, 12 lol tld....O ' 7 i:'6 9 " d0S=001. 9 7 3 ~- 2 deposition of 0.01 ~an z particles is less concentrated, though deposition is still 6 1 8 enhanced at the dividing spur. ?8 .-} t T 1" 1 These differences in the --2 16 a4 52 70 88 t8 X X shapes and locations of Number of slep~ (1-1meof a step: 3xlO'5 s) Numberof steps: ITimeo~a step: 3x10"5sl deposition hot spots can be 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 46 97 11749 64 1559 62 68 65 132 50 75874 515 2131 279 102 127 144 152 ascribed to the respective deposition mechanisms operating at 10 and 0.01 ~'n Fig. 1: Computed trajectories of 10 and 0.01 I~m unit density particles particle sizes, i.e., impaction and their initial positions at the inlet of the parent airway for the case for large particles and con- that daughter airway B is totally blocked at its end. vective diffusion and secondary flows for ultrafine d.=O.OI~ pro'titles.
109gl
' '"i'
dTl=Opm ' ~
s=~
,N=512
Oooo)
Daught~r-~x ~ /''/ (1000) ( d
ACKNOWLEDGEMENTS
This project was funded by the Austrian Fends zur FOrdortmg der wissenschaftlichen Forschung through Project P8956-MED and through Lise-Meitner-Stipendium M00051-MED for Irnre Bal~Mzy. X
X'
Fig. 2: Spatial inspiratory deposition patterns of 10 and 0.01 ~tm unit density particles for the case that daughter airway B is blocked at its end (N = number of particles deposited). REFERENCES
Bal~Mzy, I., W. Hofmann (1993) Particle deposition in airway bifurcations: I. Inspiratory flow, .J. Aerosol Sci. 24, 745-772. Gl"adon, L., D. Orlicki (1990) Deposition of inhaled aerosol particles m a generation of the traehcobronchial tree, J. AerosolSci. 21, 3-19. Kim, C.S,, A.J. Iglesias (1989) Deposition of inhaled particles in bifurcating airway models: I. Inspiratory deposition,.J. Aerosol Med. 2, 1-14. Martonen, T.B., W. Holinann (1986) Factors to be considered m a dosimclry model for risk assessment of inhaled particles, Radiat. Prot Desire. 15, 225-232. Weib¢l, E.R. (1963) Morphometry o f the Human Lung,, Springer Verlag, Heidelberg.
Copyright(~1994 Elsevier Science Ltd
Pergamon
29
P
07
Prin,~e~'~,, O~,.r,,a,n. A,, r,~h,. . . . . ~, 0021-8502/94 $7.00 + 0.00
THE EFFECT OF BLOCKED BRONCHIAL AIRWAYS ON PARTICLE DEPOSITION PA'VI'ERNS WITHIN AIRWAY BIFURCATIONS
I. B A L ~ S ~ Y
AND W. HOFMANN
Institut for Physik und Biophysik, Universitat Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria
KEYWORDS
Airway Bifurcation; Particle Deposition; Airway Blockage INTRODUCTION
Experimental observations and theoretical predictions have revealed local inhomogeneities of particle deposition within bronchial bifurcation models (BaltsMzy and Hofinann, 1993; Gradon and Orlicki, 1990; Kim and Iglesias, 1989; Martonen and Hofmann, 1986). Even in a symmetrically dividing bifurcation, partial constriction or total blockage of one of the daughter airways can produce significant asymmetric flow divisions. As a result, local deposition patterns in a diseased lung may be quite different from those in a healthy lung. Such a difference in localized particle deposition has important implications for aerosol therapy and risk assessment. METHODS
The present simulations of particle deposition patterns within bronchial airway bifurcations are based on our recently developed numerical model for the calculation of air velocity fields and aerosol particle trajectories in a three-dimensional bifurcation model (Bal~hgzy and Hofinann, 1993). In this numerical model, airflow is computed by solving the Navier-Stokes equations with a finite difference technique. Trajectories of aerosol particles within the bifurcation are then simulated by considering the simultaneous effects of inertial impaction, gravitational settling, Brownian motion, and interception, utilizing Monte Carlo methods. The geometry of the bronchial bifurcation model corresponds to the dimensions specifically employed in the Kim and Inglesias (1989) experiments, which are similar to the generation 3-4 juncture in Weibel's (1963) Model A. The inspiratory flow rate in the parent airway, Q,~, of 8 L min-1 is equivalent to a respiratory minute volumen of 32 L min-1, which is characterish~ of light activity breathing conditions. Consequently, a parabolic inlet flow profile has been adopted in the parent branch. RESULTS
Consistent with the experimental procedure of Kim and Iglesias (1989), the ratio of the flow rate in daughter airway A, QdA, to that in daughter airway B, QdB, adopts values of I (normal conditions), 2, 3 and 10 (partially blocked airway B), and infinity (totally blocked airway B). Our theoretical predictions of deposition efficiencies agree favorably with the experimentally reported data. For the sake of brevity, however, only the simulations for the totally blocked case will be presented here. The trajectories of 10 and 0.01 pm unit density particles, together with their starting points, are shown in Fig. 1 for the case that daughter airway B is totally blocked. These two particle sizes were selected here to illustrate the separate effects of the impact'i0n and sedimentation (dD = 10 pal) and diffusion (dv = 0.01 pm) mechanisms on the motion of inspired aerosols. The locatitns of the particles at the en'd of each time step are marked by dots; thus the number of steps illustrates their total flight times. AS 25 S.I-GG
$483
$484
1. BAL/~SHAZY and W. HOFMANN
For both particle sizes, only ,,5 dp = 10 prn Daughter - . ~ dp =0.01 pm Daughfer-A one particle is able to exit the bifurcation, while the remai, ~ ning particles deposit on the bifurcation walls. The corresponding deposition patterns for 1000 trajectories Y [i. . . . . are displayed in Fig. 2. Inhalation of 10 tun particles produces an intense hot spot at the carinal ridge. In addition, Daughter- B a second region of enhanced deposition can be obsc=rved at a given depth in daughter airway B. On the other hand, 12 lol tld....O ' 7 i:'6 9 " d0S=001. 9 7 3 ~- 2 deposition of 0.01 ~an z particles is less concentrated, though deposition is still 6 1 8 enhanced at the dividing spur. ?8 .-} t T 1" 1 These differences in the --2 16 a4 52 70 88 t8 X X shapes and locations of Number of slep~ (1-1meof a step: 3xlO'5 s) Numberof steps: ITimeo~a step: 3x10"5sl deposition hot spots can be 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 46 97 11749 64 1559 62 68 65 132 50 75874 515 2131 279 102 127 144 152 ascribed to the respective deposition mechanisms operating at 10 and 0.01 ~'n Fig. 1: Computed trajectories of 10 and 0.01 I~m unit density particles particle sizes, i.e., impaction and their initial positions at the inlet of the parent airway for the case for large particles and con- that daughter airway B is totally blocked at its end. vective diffusion and secondary flows for ultrafine d.=O.OI~ pro'titles.
109gl
' '"i'
dTl=Opm ' ~
s=~
,N=512
Oooo)
Daught~r-~x ~ /''/ (1000) ( d
ACKNOWLEDGEMENTS
This project was funded by the Austrian Fends zur FOrdortmg der wissenschaftlichen Forschung through Project P8956-MED and through Lise-Meitner-Stipendium M00051-MED for Irnre Bal~Mzy. X
X'
Fig. 2: Spatial inspiratory deposition patterns of 10 and 0.01 ~tm unit density particles for the case that daughter airway B is blocked at its end (N = number of particles deposited). REFERENCES
Bal~Mzy, I., W. Hofmann (1993) Particle deposition in airway bifurcations: I. Inspiratory flow, .J. Aerosol Sci. 24, 745-772. Gl"adon, L., D. Orlicki (1990) Deposition of inhaled aerosol particles m a generation of the traehcobronchial tree, J. AerosolSci. 21, 3-19. Kim, C.S,, A.J. Iglesias (1989) Deposition of inhaled particles in bifurcating airway models: I. Inspiratory deposition,.J. Aerosol Med. 2, 1-14. Martonen, T.B., W. Holinann (1986) Factors to be considered m a dosimclry model for risk assessment of inhaled particles, Radiat. Prot Desire. 15, 225-232. Weib¢l, E.R. (1963) Morphometry o f the Human Lung,, Springer Verlag, Heidelberg.