The study approaches the investigations of airway morphology of the lung with a new set of imaging and cmputer graphical methods, including confocal imaging, computer-guided image acquisition,visualization and fractal graphics. The key result is that, in contrast to the belief that the design of the conductive part of the lung of smaller mammals can be decribed with a trumpet model, the findings reported here document a strongly monopodial branching pattern with the functional consequence of a variation of dead space between the trachea and the acini. This non-dichotomic structural design finds its continuation within the respiratory units as the necessary requirement for an optimal space filling and dense packing which cannot be achieved by a dichotomic branching only. Based on a computer model, computational physics tightly coupled with computer visualistics enables functional simulation of the lung model regarding gas transport. The predicted variance in the ventilation of acini gives rise to an explanation of the well-known difference between the morphologically predicted and physiologically required diffusion capacity.
1.1 Overview The precise knowledge of the three-dimensional (3-D) assembly of biological structures is still in its origin. As an example, a widely accepted concept and common belief of the structure of the airway network oflung is that of a regular, dichotomous branching pattern, also known as the trumpet model. This model, first introduced by Weibel in 1963, is often used in clinical and physiological applications. However, if this concept of dichotomy is used to model lung, a shape is obtained that is quite different from a real lung. As a matter of fact, many previous quantitative morphological and stereological investigations of lung did not concentrate on the spatial aspect of lung morphology but delivered data in a more statistical fashion. Accordingly, the functional behavior predicted by such a model becomes questionable and indeed, the morphometrically predicted lung capacity exceeds the physiological required capacity by a factor of 1.3 up to a factor of2. This problem has also been termed a paradox, as discussed by Weibel in 1983. In the rare cases where descriptive models of the mammalian bronchial tree exist, monopodial in small mammals, dichotomous in larger ones, the understanding of the historical and/or functional reasons for size-related changes in the general design is not explainable. This investigation is trying to overcome this gap by computer modeling and functional simulation.
Andres Kriete
Computer calculus computer visualistics lung model modeling pneumology radiology visualization