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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

(A) Chest pressure t → Pmanualext(t) used as an input for our model to mimic manual chest physiotherapy. Pressure is assumed homogeneous on the thorax, case with Pcp = 20 cmH2O. (B) Relative hydrodynamic resistance r variations during a manipulation with Pcp = 20 cmH2O (blue). The red line corresponds to FRC relative hydrodynamic resistance before the manipulation (r/t = 0s = 1.00), and the black line corresponds to FRC relative hydrodynamic resistance at the end of the manipulation (r/t = 230s = 0.79).
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Figure 4: (A) Chest pressure t → Pmanualext(t) used as an input for our model to mimic manual chest physiotherapy. Pressure is assumed homogeneous on the thorax, case with Pcp = 20 cmH2O. (B) Relative hydrodynamic resistance r variations during a manipulation with Pcp = 20 cmH2O (blue). The red line corresponds to FRC relative hydrodynamic resistance before the manipulation (r/t = 0s = 1.00), and the black line corresponds to FRC relative hydrodynamic resistance at the end of the manipulation (r/t = 230s = 0.79).

Mentions: Manual chest physiotherapy is performed by applying pressures on the chest with hands. The pressures are applied during the expiration phase only and practitioners are guided by chest motion and reaction to their manipulations. Although the hand locations play an important role in chest physiotherapy, our model accounts only for pressures amplitude and time dependence: pressure is applied homogeneously onto the chest. We mimicked chest physiotherapy in our model by altering the ventilation signal during expiration, as shown on Figure 4A:


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) Chest pressure t → Pmanualext(t) used as an input for our model to mimic manual chest physiotherapy. Pressure is assumed homogeneous on the thorax, case with Pcp = 20 cmH2O. (B) Relative hydrodynamic resistance r variations during a manipulation with Pcp = 20 cmH2O (blue). The red line corresponds to FRC relative hydrodynamic resistance before the manipulation (r/t = 0s = 1.00), and the black line corresponds to FRC relative hydrodynamic resistance at the end of the manipulation (r/t = 230s = 0.79).
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: (A) Chest pressure t → Pmanualext(t) used as an input for our model to mimic manual chest physiotherapy. Pressure is assumed homogeneous on the thorax, case with Pcp = 20 cmH2O. (B) Relative hydrodynamic resistance r variations during a manipulation with Pcp = 20 cmH2O (blue). The red line corresponds to FRC relative hydrodynamic resistance before the manipulation (r/t = 0s = 1.00), and the black line corresponds to FRC relative hydrodynamic resistance at the end of the manipulation (r/t = 230s = 0.79).
Mentions: Manual chest physiotherapy is performed by applying pressures on the chest with hands. The pressures are applied during the expiration phase only and practitioners are guided by chest motion and reaction to their manipulations. Although the hand locations play an important role in chest physiotherapy, our model accounts only for pressures amplitude and time dependence: pressure is applied homogeneously onto the chest. We mimicked chest physiotherapy in our model by altering the ventilation signal during expiration, as shown on Figure 4A:

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