Implementation of Charged ParticlesDeposition in Stochastic Lung Model and  Calculation of Enhanced Deposition           D...
This presentation will cover• Background of the study• Overview of the published work• Conclusions                        ...
Background    Aerosols• A system of solid or liquid particles   Dust      Smoke  suspended in air or other gaseous  envir...
Charged Particles• The Boltzmann equilibrium charge distribution represents the  charged distribution of an aerosol in cha...
Lung deposition calculations-Importance• Evaluating the efficiency of dose  deliverance i.e. how much and how long  will p...
Deposition FractionOriginal aerosol                Aerosol inhale   DF =                     Inhaling  Deposition fraction...
Human LungHead airway (HA)Air is inspired through nose or mouthdown to larynx and rest of the lung.Tracheaobronchial (TB)B...
Lung deposition mechanisms   Major:   • Diffusion   • Sedimentation   • Inertial Impaction   Minor:   • Interception   • E...
Factors that effect deposition1. Aerosol properties•   Size distribution (MMD, AMD. etc)•   Concentration•   Particle hygr...
Stochastic Lung Dosimetry Model- IDEAL• Deposition fractions and distribution within airways generations  are modeled by t...
Objectives of the study1. to implement charge particle deposition in the stochastic   human lung model (TB and Al regions)...
Charged Particles deposition ModelTracheobronchial (TB) region•   Enhanced deposition in TB region is obtained by implemen...
Results• Particle sizes   – Unit density monodisperse charge particles of 0.3, 0.6 and 1 µm diameter.• Flow rates   – For ...
Results (continued..)Enhanced deposition in TB and Al regions as function of loadedparticle charges. Deposition is calcula...
Results (continued..)Enhanced deposition of 0.6 µm     The effect of breath hold times onparticles in the lung airway     ...
Results (continued..)Enhanced deposition within the TB and Al regions as function ofparticle charge loading. The depositio...
Results (continued..)Enhanced deposition within the TB and Al regions as function ofloaded particle charges at various tid...
Results (continued..)   Enhancement factors
Conclusion• The enhanced deposition of charged particles in the Al region is  up to five times higher than in the TB regio...
Implementation of Charged Particles Deposition in Stochastic Lung Model and Calculation of Enhanced Deposition
Implementation of Charged Particles Deposition in Stochastic Lung Model and Calculation of Enhanced Deposition
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Implementation of Charged Particles Deposition in Stochastic Lung Model and Calculation of Enhanced Deposition

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Freshly generated aerosols in workplace atmosphere may have charges well above the Boltzmann equilibrium (Forsyth et al. 1998). Similarly, aerosols produced by commercial metered dose inhalers can produce elementary charges up to several ten thousands (Kwok et al. 2005). In-vivo and in-vitro experiments have shown enhanced deposition in the lung due to electro-statically charged particles. Enhanced deposition due to charged particles in the lung is mainly caused by the image charge force (Yu, 1985). Several models have been developed to predict the effect of charged particles deposition in the lung with good agreement with the experimental data (Melandri et al. 1983; Yu 1985; Hashish et al. 1994). In the present study, enhanced deposition in the human lung due to charged particles has been estimated using the stochastic airway generation model IDEAL.

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Implementation of Charged Particles Deposition in Stochastic Lung Model and Calculation of Enhanced Deposition

  1. 1. Implementation of Charged ParticlesDeposition in Stochastic Lung Model and Calculation of Enhanced Deposition Dr. Hussain Majid 1
  2. 2. This presentation will cover• Background of the study• Overview of the published work• Conclusions 2
  3. 3. Background  Aerosols• A system of solid or liquid particles Dust Smoke suspended in air or other gaseous environment called aerosol.  Types Fume Mist  Natural Aerosol - Soil Dust - Sea Salt - Volcanic Dust Clouds Pesticides - Oceanic Sulphates  Anthropogenic Aerosol - Industrial Sulphates - Soot (Black carbon) - Organic particles 3
  4. 4. Charged Particles• The Boltzmann equilibrium charge distribution represents the charged distribution of an aerosol in charge equilibrium with bipolar ions surrounding it.• Freshly generated aerosols in workplace atmosphere may have charges well above the Boltzmann equilibrium (Forsyth et al. 1998) .• Aerosols produced by commercial metered dose inhalers can produce elementary charges up to several ten thousands (Kwok et al. 2005).• In-vivo experimental studies have shown that lung deposition of particles is significantly effected by particle charges (Yu and Chandra 1977, Cohen et al. 1998).• The significance of charged particles deposition may be of more concern for aerosol therapy than for inhalation toxicology. 4
  5. 5. Lung deposition calculations-Importance• Evaluating the efficiency of dose deliverance i.e. how much and how long will particles remain in the lung.• Assessing toxic effects of airborne pollutant depositing in certain regions of the lung.• Estimation for the location of potentially induced cancer due to exposure in radiation environment. 5
  6. 6. Deposition FractionOriginal aerosol Aerosol inhale DF = Inhaling Deposition fraction is the ratio on aerosol inhaled to the total aerosol deposit in the lung. This is affected by the entry point, the orientation of the flow to the entry point, the flow rate and particle size.
  7. 7. Human LungHead airway (HA)Air is inspired through nose or mouthdown to larynx and rest of the lung.Tracheaobronchial (TB)Bronchial tree is the first part of thelung. This part directs air in to the lungEach branch in the tree splits into 2parts Parent Branch BifurcationMajor daughter Minor daughterAlveolar or Pulmonary (Al)Alveoli are located at the end of thebronchial tree and is region where gasexchange occurs. 7
  8. 8. Lung deposition mechanisms Major: • Diffusion • Sedimentation • Inertial Impaction Minor: • Interception • ElectrostaticNaso-pharyngeal:impaction, sedimentation, electrostatic(particles > 1 μm)Tracheo-bronchial:impaction, sedimentation, diffusion(particles < 1 μm)Pulmonary:sedimentation, diffusion (particles < 0.1 μm) 9
  9. 9. Factors that effect deposition1. Aerosol properties• Size distribution (MMD, AMD. etc)• Concentration• Particle hygroscopicity• Gas particle interaction• Chemical reaction• Particle surface charge Particle properties8. Air flow properties• Lung capacity• Breathing frequency• Tidal Volume12.Respiratory tract• Structure of the extrathorcic region• Lung structure and morphology• Models used: Weibel, Raabe, and Horsfield Numbering scheme of asymmetric lung model of Raabe et al. (1974). 10
  10. 10. Stochastic Lung Dosimetry Model- IDEAL• Deposition fractions and distribution within airways generations are modeled by the stochastic lung model-IDEAL• Particles inhaled follow random path in the lung – Random selection of actual path out of millions of possible pathway by tracing histories of a large number of particles• The model uses asymmetric nature of branching pattern of the lung. – Variability of lenghts and diameter of airways are described by log-normal frequency distributions• Analytical (deterministic) formulas are used for computing deposition by diffusion, sedimentation and impaction• Monte Carlo process continues even after deposition of particles within a given airway by decreasing the statistical weight of particles 11
  11. 11. Objectives of the study1. to implement charge particle deposition in the stochastic human lung model (TB and Al regions),2. to predict enhanced deposition for various charged particle at airway generation level and to compare results with previous studies3. to quantify the breathing effects on charged particle deposition and4. to calculate enhancement factors for various breathing conditions.
  12. 12. Charged Particles deposition ModelTracheobronchial (TB) region• Enhanced deposition in TB region is obtained by implementing the following efficiency equation: 1/ 2  8B   πε d 3 t0  ( q − q0 ) ηq =    0 t  where B is the mechanical mobility of the particles, t0 is the is the mean residence time, εo is the electric permittivity of air.Alveolar (Al) region• For the spherical shaped Al region, enhanced deposition is calculated by implementing the following 1/ 3 1  5Bq  2 ηq =   πε t0   d alv  0  where t0 is the particles mean residence time [in sec]. 13
  13. 13. Results• Particle sizes – Unit density monodisperse charge particles of 0.3, 0.6 and 1 µm diameter.• Flow rates – For sitting and light exercise conditions 18 and 50 L min-1 respectively (ICRP 1994).• Tidal volumes – 750 and 1250 mL and breathing cycle times are 5 and 3s respectively.• The effect of breath-hold – 2-8 Seconds• Threshold charge limit – The enhanced deposition due to particle charges q is considered proportional to increase in threshold charge limit (q – q0). 14
  14. 14. Results (continued..)Enhanced deposition in TB and Al regions as function of loadedparticle charges. Deposition is calculated for different particle sizesat oral tidal volume of 1000 cm3 and 15 breaths per minute (Flowrate of 30 L min-1). 15
  15. 15. Results (continued..)Enhanced deposition of 0.6 µm The effect of breath hold times onparticles in the lung airway charged particle deposition for 1.0generations at various particle µm size particles and 100charge loading. elementary charges. 16
  16. 16. Results (continued..)Enhanced deposition within the TB and Al regions as function ofparticle charge loading. The deposition is calculated for differentparticle sizes under sitting (tracheal flow rate 18 L min-1) and lightexercised (Flow rate 50 L min-1) breathing conditions. 17
  17. 17. Results (continued..)Enhanced deposition within the TB and Al regions as function ofloaded particle charges at various tidal volumes. The deposition iscalculated for different particle sizes and fixed breathing frequency of15 min-1. 18
  18. 18. Results (continued..) Enhancement factors
  19. 19. Conclusion• The enhanced deposition of charged particles in the Al region is up to five times higher than in the TB region and reaches a saturation level.• Within the TB-region, enhanced deposition is higher under sitting breathing than under light exercise breathing conditions.• The enhanced deposition increases with increase in VT and flow rate in Al region.• The introduction of pause time during inhalation increases the probability of increased enhanced deposition at targeeted loaction of the respiratory tract.• Hence, by introducing charged particles during inhalation, further control on targeted deposition in the respiratory tract is possible in addition to the already applied modulation of breathing and aerosol parameters.

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