Pulmonary hemodynamics during acute acid-base changes in the intact dog

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Abstract
Pulmonary artery and left atrial pressures were measured through cardiac catheters in anesthetized dogs with controlled ventilation. Cardiac output was determined by the dye-dilution technique. Pulmonary vascular resistance (PVR) was calculated from these data. Intra-pleural, intratracheal, transmural left atrial, and transmural pulmonary artery pressures and pulmonary compliance were measured to assess their effects on PVR. Metabolic alkalosis produced by infusion of NaHCO3 or 2 amino-2-(hydroxymethyl)-1, 3-propanediol resulted in a decrease in PVR, and metabolic acidosis produced by infusion of HC1 resulted in an increase in PVR. There was no consistent change in PVR during experiments in which pH was kept constant by changing ventilation during infusion of acid or base, indicating that PVR is pH dependent. Since changes in cardiac output and transmural vascular pressures were of appropriate direction and magnitude to account for changes in PVR, it could not be concluded that effects were alone due to alterations in vascular tone. PVR was correlated with pH using the classical method for calculating vascular resistance as well as the "waterfall" concept. The effect of PaCO2 on PVR independent of pH changes is unclear, since no relationship was demonstrable using the waterfall concept.