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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.

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The external view of the alveolar sac model for the different disease states investigated at a mid lung volume of 60% total lung capacity. The states were: normal conditions (A), normal material properties with an elevated internal pressure (B), one simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysematous wall and elevated internal pressure (D). It can be seen from these external views that the stress distribution on the outer wall is disrupted for both emphysema models.
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f5-copd-2-81: The external view of the alveolar sac model for the different disease states investigated at a mid lung volume of 60% total lung capacity. The states were: normal conditions (A), normal material properties with an elevated internal pressure (B), one simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysematous wall and elevated internal pressure (D). It can be seen from these external views that the stress distribution on the outer wall is disrupted for both emphysema models.

Mentions: It was possible to rotate the alveolar sac such that the simulated emphysematous area was at the back of the model and the airway opened at the top. In this orientation a cross-section could be obtained which revealed the internal stresses within the alveolus. The increased magnitude of stress on the internal walls, caused by the weaker emphysematous region and the elevated internal alveolar pressure, is highly evident in Figure 5. The introduction of emphysematous conditions within the model has also resulted in a large maximum stress region at the junction point between the internal wall and the emphysematous area. This observation is in accordance with the physiological pattern of tissue destruction in emphysema in which the alveolar septa junctions are the primary locations of tissue breakdown.


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 external view of the alveolar sac model for the different disease states investigated at a mid lung volume of 60% total lung capacity. The states were: normal conditions (A), normal material properties with an elevated internal pressure (B), one simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysematous wall and elevated internal pressure (D). It can be seen from these external views that the stress distribution on the outer wall is disrupted for both emphysema models.
© Copyright Policy
Related In: Results  -  Collection

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

f5-copd-2-81: The external view of the alveolar sac model for the different disease states investigated at a mid lung volume of 60% total lung capacity. The states were: normal conditions (A), normal material properties with an elevated internal pressure (B), one simulated emphysematous alveolar wall with normal pressure (C), and finally a simulated emphysematous wall and elevated internal pressure (D). It can be seen from these external views that the stress distribution on the outer wall is disrupted for both emphysema models.
Mentions: It was possible to rotate the alveolar sac such that the simulated emphysematous area was at the back of the model and the airway opened at the top. In this orientation a cross-section could be obtained which revealed the internal stresses within the alveolus. The increased magnitude of stress on the internal walls, caused by the weaker emphysematous region and the elevated internal alveolar pressure, is highly evident in Figure 5. The introduction of emphysematous conditions within the model has also resulted in a large maximum stress region at the junction point between the internal wall and the emphysematous area. This observation is in accordance with the physiological pattern of tissue destruction in emphysema in which the alveolar septa junctions are the primary locations of tissue breakdown.

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