Mathematical simulation of forced expiration.
Flow limitation during forced expiration is simulated by a mathematical model. This model draws on the pressure-area law obtained in the accompanying paper, and the methods of analysis for one-dimensional flow in collapsible tubes developed by Shapiro (Trans. ASME J. Biomech. Eng. 99: 126-147, 1977). These methods represent an improvement over previous models in that 1) the effects of changing lung volume and of parenchymal-bronchial interdependence are simulated; 2) a more realistic representation of collapsed airways is employed; 3) a solution is obtained mouthward of the flow-limiting site by allowing for a smooth transition from sub- to supercritical flow speeds, then matching mouth pressure by imposing an elastic jump (an abrupt transition from super- to subcritical flow speeds) at the appropriate location; and 4) the effects of levels of effort (or vacuum pressure) in excess of those required to produce incipient flow limitation are examined, including the effects of potential physiological limitation.
Elad
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Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge 02139.
Kamm
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RD
Shapiro
A H
AH
D000402:Airway Obstruction / Q000503:physiopathology; D005541:Forced Expiratory Volume; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D011312:Pressure