Limits...
Stress distribution in a three dimensional, geometric alveolar sac under normal and emphysematous conditions.

de Ryk J, Thiesse J, Namati E, McLennan G - Int J Chron Obstruct Pulmon Dis (2007)

Bottom Line: Using the model numerical analysis of the stress distribution in normal conditions could be compared with those resulting in emphysematous conditions.When internal alveolar pressure was increased along with the adjustment of the material properties to represent a weakening of one wall in the acinus, increased stress resulted at the perimeters of the weakened area.It was also found that under the proposed simulated emphysematous conditions, a significant disruption in the stress distribution within the acinus model occurred at low, rather than high, lung volumes.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.

ABSTRACT
Pulmonary emphysema is usually the result of chronic exposure to cigarette smoke in at risk individuals. To investigate the hypothesis that lung damage in emphysema results from coincident weakening in the structural properties of the tissue and increased mechanical forces--as one explanation of the continued development of pulmonary emphysema after smoking cessation--we developed a three dimensional, geometric dodecahedron-based acinar model. Using the model numerical analysis of the stress distribution in normal conditions could be compared with those resulting in emphysematous conditions. Finite element analysis was used to evaluate the model at a number of lung inflation levels, using quasi-static loading of the alveolar pressure. When internal alveolar pressure was increased along with the adjustment of the material properties to represent a weakening of one wall in the acinus, increased stress resulted at the perimeters of the weakened area. In particular this increased stress was localized at the junction points of the internal alveolar septa. It was also found that under the proposed simulated emphysematous conditions, a significant disruption in the stress distribution within the acinus model occurred at low, rather than high, lung volumes. This is supportive of the physiological observation that destruction of the diseased tissue can occur under less stress than those existing in the normal state.

Show MeSH

Related in: MedlinePlus

The stacked rhombic dodecahedron alveolar sac model displayed from four different angles: an oblique view (A), a base view with a −15 degree x-axis rotation (B), a base view with a 15 degree x-axis rotation (C), and a base view with a 45 degree x-axis rotation (D).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2692121&req=5

f1-copd-2-81: The stacked rhombic dodecahedron alveolar sac model displayed from four different angles: an oblique view (A), a base view with a −15 degree x-axis rotation (B), a base view with a 15 degree x-axis rotation (C), and a base view with a 45 degree x-axis rotation (D).

Mentions: The desired alveolar sac model featured a central rhombic dodecahedron surrounded by twelve adjoining dodecahedra. The walls of the central polyhedron were then removed to form a central open space connecting the surrounding dodecahedra. One of the external walls was also removed to create an opening to simulate the connection of a small airway to the alveolar sac (Figure 1).


Stress distribution in a three dimensional, geometric alveolar sac under normal and emphysematous conditions.

de Ryk J, Thiesse J, Namati E, McLennan G - Int J Chron Obstruct Pulmon Dis (2007)

The stacked rhombic dodecahedron alveolar sac model displayed from four different angles: an oblique view (A), a base view with a −15 degree x-axis rotation (B), a base view with a 15 degree x-axis rotation (C), and a base view with a 45 degree x-axis rotation (D).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2692121&req=5

f1-copd-2-81: The stacked rhombic dodecahedron alveolar sac model displayed from four different angles: an oblique view (A), a base view with a −15 degree x-axis rotation (B), a base view with a 15 degree x-axis rotation (C), and a base view with a 45 degree x-axis rotation (D).
Mentions: The desired alveolar sac model featured a central rhombic dodecahedron surrounded by twelve adjoining dodecahedra. The walls of the central polyhedron were then removed to form a central open space connecting the surrounding dodecahedra. One of the external walls was also removed to create an opening to simulate the connection of a small airway to the alveolar sac (Figure 1).

Bottom Line: Using the model numerical analysis of the stress distribution in normal conditions could be compared with those resulting in emphysematous conditions.When internal alveolar pressure was increased along with the adjustment of the material properties to represent a weakening of one wall in the acinus, increased stress resulted at the perimeters of the weakened area.It was also found that under the proposed simulated emphysematous conditions, a significant disruption in the stress distribution within the acinus model occurred at low, rather than high, lung volumes.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.

ABSTRACT
Pulmonary emphysema is usually the result of chronic exposure to cigarette smoke in at risk individuals. To investigate the hypothesis that lung damage in emphysema results from coincident weakening in the structural properties of the tissue and increased mechanical forces--as one explanation of the continued development of pulmonary emphysema after smoking cessation--we developed a three dimensional, geometric dodecahedron-based acinar model. Using the model numerical analysis of the stress distribution in normal conditions could be compared with those resulting in emphysematous conditions. Finite element analysis was used to evaluate the model at a number of lung inflation levels, using quasi-static loading of the alveolar pressure. When internal alveolar pressure was increased along with the adjustment of the material properties to represent a weakening of one wall in the acinus, increased stress resulted at the perimeters of the weakened area. In particular this increased stress was localized at the junction points of the internal alveolar septa. It was also found that under the proposed simulated emphysematous conditions, a significant disruption in the stress distribution within the acinus model occurred at low, rather than high, lung volumes. This is supportive of the physiological observation that destruction of the diseased tissue can occur under less stress than those existing in the normal state.

Show MeSH
Related in: MedlinePlus