Intrapulmonary Gas Mixing in Panacinar- and Centriacinar-Induced Emphysema in Rats

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Abstract
We studied ventilation distribution using the single-breath washout technique in rats with two types of induced emphysema: panacinar-like (by instilled elastase) and centriacinar-like (by inhaled CdCl 2 combined with oral intake of b -aminopropionitrile). Morphologically, panacinar and centriacinar groups presented a similar degree of airspace enlargement, which was irregularly distributed and also accompanied by fibrosis only in the centriacinar group. In terms of mechanical properties, the centriacinar group presented lower end-expiratory flows and lower compliance than the panacinar group. The ventilation distribution patterns were also different between both groups. Single-breath washout phase III slopes, reflecting mainly diffusion-convection-dependent inhomogeneities in rat lungs, were largest in the centriacinar group. The SF 6 -He slope difference, which was reversed in both emphysema groups with respect to the control group, could be attributed mainly to He slope changes in the panacinar group and to SF 6 slope changes in the centriacinar group. In addition, the respective He and SF 6 slope decrease as a function of end-inspiratory breath-hold time, was only dif- ferent from the control group in the centriacinar group. The observed ventilation distribution pat- terns can be explained by interacinar elastic changes in the panacinar group and severe interacinar structural alterations in the centriacinar group. Rubio ML, Sánchez-Cifuentes MV, Peces-Barba G, Verbanck S, Paiva M, González Mangado N. Intrapulmonary gas mixing in panacinar- and centriacinar - induced emphysema in rats.