Estimation of isogravimetric capillary pressure by a filtration method in skeletal muscle and lung.

Pre- to postcapillary resistance ratios (Ra/Rv) and isogravimetric capillary pressures (Pc,i) were estimated using a modified filtration method and compared with estimates obtained by application of traditional isogravimetric techniques in isolated rat hindquarters and canine lungs. Pc,i's and Ra/Rv's were estimated using both methods in rat hindquarters perfused with whole blood or an artificial plasma and in blood-perfused canine lung. In each of the three experimental conditions studied, the modified filtration method yielded the same Pc,i and Ra/Rv as the isogravimetric technique. Maximal vasodilation of the rat hindquarter with papaverine reduced Ra/Rv approximately fourfold to a level which was not different from that obtained in hindquarters perfused with artificial plasma, although Pc,i was unchanged. These results indicate that the more easily applied modified filtration method provides an excellent measurement of Ra/Rv and Pc,i in whole organ studies.