Tissue heterogeneity in the mouse lung: effects of elastase treatment.
We developed a network model in an attempt to characterize heterogeneity of tissue elasticity of the lung. The model includes a parallel set of pathways, each consisting of an airway resistance, an airway inertance, and a tissue element connected in series. The airway resistance, airway inertance, and the hysteresivity of the tissue elements were the same in each pathway, whereas the tissue elastance (H) followed a hyperbolic distribution between a minimum and maximum. To test the model, we measured the input impedance of the respiratory system of ventilated normal and emphysematous C57BL/6 mice in closed chest condition at four levels of positive end-expiratory pressures. Mild emphysema was developed by nebulized porcine pancreatic elastase (PPE) (30 IU/day x 6 days). Respiratory mechanics were studied 3 wk following the initial treatment. The model significantly improved the fitting error compared with a single-compartment model. The PPE treatment was associated with an increase in mean alveolar diameter and a decrease in minimum, maximum, and mean H. The coefficient of variation of H was significantly larger in emphysema (40%) than that in control (32%). These results indicate that PPE treatment resulted in increased time-constant inequalities associated with a wider distribution of H. The heterogeneity of alveolar size (diameters and area) was also larger in emphysema, suggesting that the model-based tissue elastance heterogeneity may reflect the underlying heterogeneity of the alveolar structure.
Ito
Satoru
S
Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
Ingenito
Edward P
EP
Arold
Stephen P
SP
Parameswaran
Harikrishnan
H
Tgavalekos
Nora T
NT
Lutchen
Kenneth R
KR
Suki
Béla
B
D000403:Airway Resistance / Q000187:drug effects; D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D004548:Elasticity / Q000187:drug effects*; D016014:Linear Models; D008168:Lung / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D010196:Pancreatic Elastase / Q000494:pharmacology*; D011175:Positive-Pressure Respiration; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000502:physiology; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000187:drug effects; D013552:Swine
D010196:Pancreatic Elastase