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 internal view of the alveolar sac model at a lung volume of 60% total lung capacity showing the model sliced through the medial plane to reveal the inner wall of the emphysematous area. The states illustrated are: normal conditions (A), normal with an elevated internal pressure (B), a simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysemic wall and elevated internal pressure (D). These internal views highlight the elevated stress through out the internal emphysematous wall, with particularly high stresses at the wall junction sites.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2692121&req=5

f6-copd-2-81: The internal view of the alveolar sac model at a lung volume of 60% total lung capacity showing the model sliced through the medial plane to reveal the inner wall of the emphysematous area. The states illustrated are: normal conditions (A), normal with an elevated internal pressure (B), a simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysemic wall and elevated internal pressure (D). These internal views highlight the elevated stress through out the internal emphysematous wall, with particularly high stresses at the wall junction sites.

Mentions: A comparison has been made between the stress intensity contour plots of the geometric model under different conditions (Figures 5 and 6). These results demonstrate the stress distribution of the alveolar sac model under normal conditions, normal tissue properties with elevated internal alveolar pressure, and an emphysematous area with no increased internal alveolar pressure and finally, an emphysematous area with increase internal alveolar pressure. The same color scale is used for each set such that they can be directly compared with each other. Figure 5 illustrates the stress distribution on the outer wall of the alveolar sac whereas Figure 6 reveals the stress distribution on the inner wall. Figure 7 allows a close up examination of the elevated stress regions at the alveolar wall junctions in the simulated emphysematous area accompanied by increased alveolar pressure.


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 internal view of the alveolar sac model at a lung volume of 60% total lung capacity showing the model sliced through the medial plane to reveal the inner wall of the emphysematous area. The states illustrated are: normal conditions (A), normal with an elevated internal pressure (B), a simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysemic wall and elevated internal pressure (D). These internal views highlight the elevated stress through out the internal emphysematous wall, with particularly high stresses at the wall junction sites.
© Copyright Policy
Related In: Results  -  Collection

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

f6-copd-2-81: The internal view of the alveolar sac model at a lung volume of 60% total lung capacity showing the model sliced through the medial plane to reveal the inner wall of the emphysematous area. The states illustrated are: normal conditions (A), normal with an elevated internal pressure (B), a simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysemic wall and elevated internal pressure (D). These internal views highlight the elevated stress through out the internal emphysematous wall, with particularly high stresses at the wall junction sites.
Mentions: A comparison has been made between the stress intensity contour plots of the geometric model under different conditions (Figures 5 and 6). These results demonstrate the stress distribution of the alveolar sac model under normal conditions, normal tissue properties with elevated internal alveolar pressure, and an emphysematous area with no increased internal alveolar pressure and finally, an emphysematous area with increase internal alveolar pressure. The same color scale is used for each set such that they can be directly compared with each other. Figure 5 illustrates the stress distribution on the outer wall of the alveolar sac whereas Figure 6 reveals the stress distribution on the inner wall. Figure 7 allows a close up examination of the elevated stress regions at the alveolar wall junctions in the simulated emphysematous area accompanied by increased alveolar pressure.

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