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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.


Evolution of mucus distribution in the bronchi during the manipulation, with Pcp = 20 cmH2O. The blue bars correspond to the surface of bronchi lumen area relatively to bronchi initial surface. The green bars correspond to the surface fraction of bronchi lumen area obstructed by secretions. At the end of manipulation, secretions have been globally motioned upward the tree, however some secretions have been pushed deeper in the lung, see generation 11–13.
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Figure 6: Evolution of mucus distribution in the bronchi during the manipulation, with Pcp = 20 cmH2O. The blue bars correspond to the surface of bronchi lumen area relatively to bronchi initial surface. The green bars correspond to the surface fraction of bronchi lumen area obstructed by secretions. At the end of manipulation, secretions have been globally motioned upward the tree, however some secretions have been pushed deeper in the lung, see generation 11–13.

Mentions: Secretions distribution in the tree are motioned from one generation to the next, and because manipulation pressures are applied during expiration, mucus tends to go up the tree, at least for moderate pressures amplitude, see Figure 5C. The mechanism is as follow: during pressure application, secretions are moving upward in the tree from one generation to the next, and thus fill the upper generations. Lung's recoil from the manipulation and lung opening due to inspiration are correlated to an inlet air flow in the lung, which potentially moves the secretions back into the lower generations. This backward secretions motion depends on how much secretions have accumulated during the pressure application. If the pressure is high, then secretions accumulate a lot in the upper bronchi, reducing drastically air lumen area, and by thus they are more affected by the inward air flow. This is why for high pressures, although there is less secretions in the tree at then end, they are globally deeper after the manipulation than before the manipulation. This phenomenon can be seen on Figure 6 where generations 11–13 have more secretions at the end of the manipulation.


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)

Evolution of mucus distribution in the bronchi during the manipulation, with Pcp = 20 cmH2O. The blue bars correspond to the surface of bronchi lumen area relatively to bronchi initial surface. The green bars correspond to the surface fraction of bronchi lumen area obstructed by secretions. At the end of manipulation, secretions have been globally motioned upward the tree, however some secretions have been pushed deeper in the lung, see generation 11–13.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Evolution of mucus distribution in the bronchi during the manipulation, with Pcp = 20 cmH2O. The blue bars correspond to the surface of bronchi lumen area relatively to bronchi initial surface. The green bars correspond to the surface fraction of bronchi lumen area obstructed by secretions. At the end of manipulation, secretions have been globally motioned upward the tree, however some secretions have been pushed deeper in the lung, see generation 11–13.
Mentions: Secretions distribution in the tree are motioned from one generation to the next, and because manipulation pressures are applied during expiration, mucus tends to go up the tree, at least for moderate pressures amplitude, see Figure 5C. The mechanism is as follow: during pressure application, secretions are moving upward in the tree from one generation to the next, and thus fill the upper generations. Lung's recoil from the manipulation and lung opening due to inspiration are correlated to an inlet air flow in the lung, which potentially moves the secretions back into the lower generations. This backward secretions motion depends on how much secretions have accumulated during the pressure application. If the pressure is high, then secretions accumulate a lot in the upper bronchi, reducing drastically air lumen area, and by thus they are more affected by the inward air flow. This is why for high pressures, although there is less secretions in the tree at then end, they are globally deeper after the manipulation than before the manipulation. This phenomenon can be seen on Figure 6 where generations 11–13 have more secretions at the end of the manipulation.

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.