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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.


(A) Volume of secretions expelled at the end of the manipulation as a function of the pressure amplitude. (B) Relative hydrodynamic resistance of the tree at the end of manipulation as a function of the pressure amplitude. (C) Mean secretions position in the tree as a function of the pressure amplitude. Mean position is expressed in generation index.
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Figure 5: (A) Volume of secretions expelled at the end of the manipulation as a function of the pressure amplitude. (B) Relative hydrodynamic resistance of the tree at the end of manipulation as a function of the pressure amplitude. (C) Mean secretions position in the tree as a function of the pressure amplitude. Mean position is expressed in generation index.

Mentions: We investigated the role of pressure Pcp amplitude on mucus motion and distribution and on hydrodynamic resistance changes. Smaller chest pressures induce smaller air velocities and thus smaller shear stresses in the bronchi. As a consequence, the stress threshold that has to be overcome for secretions to be mobilized is only reached in highly obstructed bronchi. But the motion is quickly stopped when a new equilibrium between air flow and secretions distribution is reached. In particular, for chest pressures lower than 16.5 cmH2O, we do not observe in the model any secretions going out of the lung, see Figure 5A. This does not mean however that secretions distribution has not been affected, as shown on Figure 5B. An important point is that by performing the manipulation, secretions are moving in such a way that their distribution always decreases the total hydrodynamic resistance of the tree, down to a value corresponding to an equilibrium between secretions and air flows. The first steps of the manipulations are the more efficient, as shown on Figure 4B. The higher the pressure, the lowest is the tree hydrodynamic resistance at the end of the manipulation. The first conclusion is then that the manipulations decrease the hydrodynamic resistance of the patient, which may lead to an improvement of patient breathing quality, even if no secretions get out of the tree.


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)

(A) Volume of secretions expelled at the end of the manipulation as a function of the pressure amplitude. (B) Relative hydrodynamic resistance of the tree at the end of manipulation as a function of the pressure amplitude. (C) Mean secretions position in the tree as a function of the pressure amplitude. Mean position is expressed in generation index.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: (A) Volume of secretions expelled at the end of the manipulation as a function of the pressure amplitude. (B) Relative hydrodynamic resistance of the tree at the end of manipulation as a function of the pressure amplitude. (C) Mean secretions position in the tree as a function of the pressure amplitude. Mean position is expressed in generation index.
Mentions: We investigated the role of pressure Pcp amplitude on mucus motion and distribution and on hydrodynamic resistance changes. Smaller chest pressures induce smaller air velocities and thus smaller shear stresses in the bronchi. As a consequence, the stress threshold that has to be overcome for secretions to be mobilized is only reached in highly obstructed bronchi. But the motion is quickly stopped when a new equilibrium between air flow and secretions distribution is reached. In particular, for chest pressures lower than 16.5 cmH2O, we do not observe in the model any secretions going out of the lung, see Figure 5A. This does not mean however that secretions distribution has not been affected, as shown on Figure 5B. An important point is that by performing the manipulation, secretions are moving in such a way that their distribution always decreases the total hydrodynamic resistance of the tree, down to a value corresponding to an equilibrium between secretions and air flows. The first steps of the manipulations are the more efficient, as shown on Figure 4B. The higher the pressure, the lowest is the tree hydrodynamic resistance at the end of the manipulation. The first conclusion is then that the manipulations decrease the hydrodynamic resistance of the patient, which may lead to an improvement of patient breathing quality, even if no secretions get out of the tree.

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.