Experimental simulation trial for human lung's flow mechanism ARA - PowerPoint PPT Presentation

ヒトの肺の流れの力学解明に向けた実験的シミュレーション Experimental simulation trial for human lung's flow mechanism ARA 平原裕行 Hi Hiroyu oyuki ki HI HIRAH AHAR Division of Human Support and Production Science 人間支援・生産科学部門 Saitama University 埼玉大学 2016/6/10 1

Get ‘REAL SOLUTION’ ? Or Get ‘ESSENCE’? Promoting Way Conventional Way EFD CFD EFD CFD Check and Review V & V For Inovation 2016/5/09 2

Today’s presentation What we should remove from complex factor ? 1) Irreversible Laminar Flow in Peripheral Lungs Complete viscous (laminar) ! But, something happen. 2) Coanda effect simulation Potential ? or Viscous ? 3

2 23 bifurcations makes intricate structure Oxygen-rich Nasal Pharynx Trachea Bronchi air from cavities environment Oxygen and carbon dioxide Bronchi Bronchioles Alveoli Bronchioles exchange at alveoli Carbon Nasal Trachea Pharynx dioxide-rich cavities air to the environment Fig.2 Delivery of Oxygen and Carbon Dioxide Fig.1 Macroscopic view of a plastic cast of the airways (yellow) the pulmonary In the Respiratory System arteries (red) and veins (blue) of a human lung. (Anatomy Institute of Anatomy, University of Berne, Switzerland) 2016/5/09 4

High-frequency oscillatory ventilation: Mechanisms of gas exchange and lung mechanics J. Jane Pillow, MBBS, FRACP, PhD Crit Care Med 2005 Vol. 33, No. 3 (Suppl.)

General CHANG, H. K. Mechanisms of gas transport during ventilation by high frequency oscillation. J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 56( 3): 553-563, 1984.- 5 flow modes by Chang(1984) Ventilation by high-frequency oscillation (HFO) presents some difficulties in understanding exactly how gas is transported in the lung. However, at a qualitative level, five modes of transport may be identified: 1 ) direct alveolar ventilation in the lung units situated near the airway opening; 2) bulk result of recirculation of convective mixing air among units of in the conducting airways as a inhomogeneousti me constants; 3) convective transport of gases-as a result of the asymmetry between inspiratory and expiratory velocity profiles; 4) longitudinal dispersion caused by the interaction between axial velocities and radial transports due to turbulent eddies and/or secondary swirling motions 5) molecular diffusion near the alveolocapillary membrane. These modes of transport are not mutually exclusive and certainly interact. It is therefore difficult to make quantitative predictions about the overall rate of transport. Qualitatively, it may now be stated with confidence that convective transport in the tracheobronchial tree is very important during HFO as in normal breathing and . that increasing tidal volu .me is more effective than increa sing frequency in improving gas exchange during HFO. To optimi .ze the gas transport efficiency of HFO, future research should focus on identifying the rate-li .miting mode of transport for a given set of geometric and dynamic conditions. FIG. 9. Modes of gas transport during high-frequency oscillation (HFO) and tentative sketch of their zones of dominance. These modes of transport are not mutually exclusive and may interact to achieve observed efficiency in animal or patient studies.

3. GAS FLOW IN BRONCHIOLES INDUCED BY HFOV 3.1 Introduction of HFOV Pendelluft Flow Fig.19 Illustration of Pendelluft mechanism (H. Hirahara) Taylor Coaxial Flow Dispersion Flow Fig.20 Velocity distribution in the bifurcation plane and two cross sections at 7 th generation: (A) end inspiration, (B) end 2016/5/09 7 expiration. Blue, negative axial velocity to the left; Red, positive axial velocity to the right. (Choi et al. 2010)

What parameters should be considered ? Fig.3 Flow regimes of the conducting airway categorized on the basis of a Fig.4 Re , Pe , and Wo numbers for T V =150mL at each generation. dimensionless frequency α 2 (where α is the Womersley number) and a (Hirahara, 2010, J of Fluid and Science Technology) dimensionless stroke length L/a. Jan et al. 2016/5/09 8

Reynolds number is not only similarity parameter, But also momentum diffusion speed ! 𝑆𝑓 = 𝑉𝑀 𝜉 = 𝑉 Convective speed 𝜉/𝑀 = Momentum Diffusion speed 𝜉: viscousity Peclet number is also important, 𝑄𝑓 = 𝑉𝑀 𝛽 = 𝑉 Convective speed 𝛽/𝑀 = Molecular Diffusion speed 9 𝛽: 𝑛olacular diffusion coefficient

Why we will not use CT data ? 1. The Weibel’s lung model is symmetric and relatively simple, it helps to diminish the disturbance of over-complex structure, to get more general and representative gas flow phenomena. 2. The weibel’s lung model facilitates not only numerical simulation but also PIV experiment. 2016/5/09 10 Fig.5 Bifurcating structure of human lung based on Weibel’s model

Why the bronchioles is target ? (below G18) 1. Almost all researchers focus on upper-airway flow above G10. What happens at the distal region? 2. HFOV adopts fast and shallow oscillatory ventilation, the small tidal volume cannot reach the respiratory zone at each oscillation. How can HFOV be effective in ventilation? How can fresh gas reach the distal region? only by molecular diffusion? Or by some progressive delivery? 2016/5/09 11 Fig.6 Illustration of main research region and reachable area of single tidal volume of HFOV

What happens in High frequency respiration ? Normal  HVOV  Super-HFOV Conventional Ventilation High Frequency Super-High Frequency Or Normal Breathing Oscillatory Ventilation Oscillatory Ventilation 100Hz… f About 10Hz About 0.2Hz 5ml 10ml… T V About 50ml About 500ml V T (constant) = f × T V Basic principle: 2016/5/09 12

Numerical modeling Inlet Outlets Dimensions of mother to grand-daughter tubes from G18 to G20 (left) and volume mesh (right) 2016/5/09 13

Fundamental condition of CFD Governing Equations Boundary conditions for inlet Boundary conditions for outlets Boundary conditions for peripheral wall Rigid wall with non-slip condition without molecular diffusion without turbulent model

Gas exchange in ‘Normal Breath’ at different position Fig.8 Lagrangian particles setting Fig.9 Setting for VOF Fig.10 Setting for VOF calculation by 2 fluids calculation with 4 fluids at different locations (Molecular diffusion neglected) (Molecular diffusion neglected) 2016/5/09 15

Gas exchange in ‘Normal Breath’ at different position Fig.11 Particle fluctuations in G18-G20 by CV (sinusoidal, 0.2Hz, 500mL) in 5 seconds 2016/5/09 16

Gas exchange in ‘Normal Breath’ at different position VOF calculation for Normal Breath (sinusoidal, 0.2Hz, 500mL) in 5 seconds 17 2016/5/09

Gas exchange in ‘Normal Breath’ 5 seconds later Gas redistribution due to large TV 2016/5/09 18

Fig.22 Lagrangian particles at the same locations of Fig.23 Setting for VOF Fig.24 Setting for VOF calculation with 2 fluids calculation with 4 fluids VOF interfaces in Fig.12 (Molecular diffusion neglected) (Molecular diffusion neglected) 2016/5/09 19

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV 2016/5/09 20 Fig.25 Particle fluctuations in G18-G20 by HFOV (sinusoidal, 10Hz, 50mL) in 5 seconds

3-D View of Lagrangian tracking Redistribution of massless particles caused by raking effect in G18 with HFOV(Sinusoidal, 10Hz, 50ml) in 3 cycles (0.3seconds) 2016/5/09 21

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV Fig.26 VOF calculation for HFOV (10Hz, 50mL, sinusoidal) in 5 seconds 2016/5/09 22

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV 0 second 0.3 seconds 1 second 5 seconds Fig.27 VOF calculation for HFOV (10Hz, 50mL, sinusoidal) in 5 seconds 2016/5/09 23

Normal HFOV VS VS Fig.28 Comparison of gas rearrangement in G18-G20 with CV (sinusoidal, 0.2Hz, 500mL) and HFOV (sinusoidal, 10Hz, 50mL) in 5 seconds

Conclusion 1 HFOV rakes the gas near the central-axis downwards and the peripheral gas upwards much more than CV does, which is named raking effect here, it features similar effect of the coaxial counter-flow. Conclusion 2 A significant difference between raking effect and counter-flow is that raking effect doesn’t apparently involve flows in two opposite directions simultaneously. Raking effect can be seen due to irreversibility as a time- average effect in laminar flow within a tiny space where viscous force is dominant. 2016/5/09 25

Micro-PIV(Particle Image velocimetry) Measurement PIV experiment in Real Scale ! 2016/5/09 26

Phase locked ensemble averaged profiles 1 2 3 4 Fig.48 Experiment result of velocity vectors in one cycle No obvious coaxial counter-flow as with small lung model and HFOV (Sinusoidal, 10Hz, 50ml) 1.When inhaling velocity maximizes. 2.When exhaling velocity maximizes. 2016/5/09 27 same as CFD 3.End of inhalation. 4.End of exhalation.

Lagrangian tracking shows the ‘ raking effect’ (2) (1) Fig.49 Experiment result of particle tracks in one cycle with small lung model and HFOV (Sinusoidal, 50ml, 10Hz(1) /20Hz (2)) 2016/5/09 28