The Effect of Changes in Arterial PCO2 on Isogravimetric Capillary Pressure and Vascular Resistances

摘要

One study was designed to determine the effect of a changing arterial pCO2 on capillary permeability and pre- and postcapillary resistances. Experiments were carried out on isolated forelimbs of dogs perfused with blood equilibrated with different CO2 pressures in an isolated lung. Gas mixtures containing 0%, 5%, and 10% CO2 resulted in arterial mean pCO2 values of 12, 48 and 78 mm Hg. Isogravimetric capillary pressure (Pci) was measured using a modified Pappenheimer and Soto-Rivera technique. Results show the mean Pci rising from 13 to 14.7 mm Hg (p = 0.04) after pCO2 was increased from 48 to 78 mm Hg. When the pCO2 was lowered to 12 mm Hg, Pci fell to 10.1 mm Hg (p = 0.016). Precapillary resistance fell with an increased pCO2 and rose with a decreased pCO2. Effects of pCO2 were believed to alter the permeability of the capillaries due to a direct action on the capillary membrane. The observed changes in capillary permeability are interpreted as a protective mechanism opposed to effects of alterations of capillary hydrostatic pressure resulting from changes in blood pCO2. (Author)