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Toward the modeling of mucus draining from human lung: role of airways deformation on air-mucus interaction.

Mauroy B, Flaud P, Pelca D, Fausser C, Merckx J, Mitchell BR - Front Physiol (2015)

Bottom Line: Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions.Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs.Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire J. A. Dieudonnée - UMR CNRS 7351, Université de Nice-Sophia Antipolis Nice, France.

ABSTRACT
Chest physiotherapy is an empirical technique used to help secretions to get out of the lung whenever stagnation occurs. Although commonly used, little is known about the inner mechanisms of chest physiotherapy and controversies about its use are coming out regularly. Thus, a scientific validation of chest physiotherapy is needed to evaluate its effects on secretions. We setup a quasi-static numerical model of chest physiotherapy based on thorax and lung physiology and on their respective biophysics. We modeled the lung with an idealized deformable symmetric bifurcating tree. Bronchi and their inner fluids mechanics are assumed axisymmetric. Static data from the literature is used to build a model for the lung's mechanics. Secretions motion is the consequence of the shear constraints apply by the air flow. The input of the model is the pressure on the chest wall at each time, and the output is the bronchi geometry and air and secretions properties. In the limit of our model, we mimicked manual and mechanical chest physiotherapy techniques. We show that for secretions to move, air flow has to be high enough to overcome secretion resistance to motion. Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions. However, pressures too high are efficient up to a point where airways compressions prevents air flow to increase any further. Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs. Also, some secretions might be pushed deeper into the lungs; this effect is stronger for high pressures and for mechanical chest physiotherapy. Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

No MeSH data available.


Related in: MedlinePlus

Dependence of bronchi surface area (normalized) with bronchi transmural pressure. The numbers correspond to the generation index and the red dashed line represents bronchi state at FRC.
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Figure 2: Dependence of bronchi surface area (normalized) with bronchi transmural pressure. The numbers correspond to the generation index and the red dashed line represents bronchi state at FRC.

Mentions: To compute airways diameters, we used data from Lambert et al. (1982). Lambert et al. built data based static relationships of bronchi's airways lumen area vs. their transmural pressure for the seventeenth first generations. Their estimations are given per generation. For an airway belonging to generation z with a transmural pressure ΔP, they proposed that the airway lumen area Sz(Δp) is a sigmoid function of transmural pressure:(1)𝒮z(ΔP)={α0(z)(1−ΔPP1(z))−n1(z)Am(z)when ΔP≤0(1−(1−α0(z))(1−ΔPP2(z))n2(z))         Am(z)when ΔP>0with and . Am represents the maximal possible lumen area. The quantity α0Am is the airway area when transmural pressure is 0. At functional residual regime (FRC, end of normal expiration), the transmural pressure is about 500 Pa. The values used for the different parameters in the previous formulas are detailed in Table 2; the dependence of the bronchi surface area with transmural pressure are plotted on Figure 2.


Toward the modeling of mucus draining from human lung: role of airways deformation on air-mucus interaction.

Mauroy B, Flaud P, Pelca D, Fausser C, Merckx J, Mitchell BR - Front Physiol (2015)

Dependence of bronchi surface area (normalized) with bronchi transmural pressure. The numbers correspond to the generation index and the red dashed line represents bronchi state at FRC.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525672&req=5

Figure 2: Dependence of bronchi surface area (normalized) with bronchi transmural pressure. The numbers correspond to the generation index and the red dashed line represents bronchi state at FRC.
Mentions: To compute airways diameters, we used data from Lambert et al. (1982). Lambert et al. built data based static relationships of bronchi's airways lumen area vs. their transmural pressure for the seventeenth first generations. Their estimations are given per generation. For an airway belonging to generation z with a transmural pressure ΔP, they proposed that the airway lumen area Sz(Δp) is a sigmoid function of transmural pressure:(1)𝒮z(ΔP)={α0(z)(1−ΔPP1(z))−n1(z)Am(z)when ΔP≤0(1−(1−α0(z))(1−ΔPP2(z))n2(z))         Am(z)when ΔP>0with and . Am represents the maximal possible lumen area. The quantity α0Am is the airway area when transmural pressure is 0. At functional residual regime (FRC, end of normal expiration), the transmural pressure is about 500 Pa. The values used for the different parameters in the previous formulas are detailed in Table 2; the dependence of the bronchi surface area with transmural pressure are plotted on Figure 2.

Bottom Line: Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions.Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs.Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire J. A. Dieudonnée - UMR CNRS 7351, Université de Nice-Sophia Antipolis Nice, France.

ABSTRACT
Chest physiotherapy is an empirical technique used to help secretions to get out of the lung whenever stagnation occurs. Although commonly used, little is known about the inner mechanisms of chest physiotherapy and controversies about its use are coming out regularly. Thus, a scientific validation of chest physiotherapy is needed to evaluate its effects on secretions. We setup a quasi-static numerical model of chest physiotherapy based on thorax and lung physiology and on their respective biophysics. We modeled the lung with an idealized deformable symmetric bifurcating tree. Bronchi and their inner fluids mechanics are assumed axisymmetric. Static data from the literature is used to build a model for the lung's mechanics. Secretions motion is the consequence of the shear constraints apply by the air flow. The input of the model is the pressure on the chest wall at each time, and the output is the bronchi geometry and air and secretions properties. In the limit of our model, we mimicked manual and mechanical chest physiotherapy techniques. We show that for secretions to move, air flow has to be high enough to overcome secretion resistance to motion. Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions. However, pressures too high are efficient up to a point where airways compressions prevents air flow to increase any further. Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs. Also, some secretions might be pushed deeper into the lungs; this effect is stronger for high pressures and for mechanical chest physiotherapy. Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

No MeSH data available.


Related in: MedlinePlus