A comparison of pulmonary arterial occlusion algorithms for estimation of pulmonary capillary pressure

Using the arterial occlusion method, we compared five literature-based esti mates of pulmonary capillary pressure (Ppc) with the corresponding double o cclusion pressures (Pdo) in anesthetized dogs whose chests had been closed after sternotomy for instrumentation. Arterial occlusions were performed wi th a balloon-tipped pulmonary artery catheter that housed pressure transduc ers immediately proximal and distal to the balloon. Separation of the proxi mal and distal pressure waveforms during balloon inflation allowed us to pr ecisely define the moment of occlusion. We fit a monoexponential curve to p ressure data beginning 200 ms after the onset of occlusion and a biexponent ial curve to data beginning at the instant of occlusion, with data obtained over a range of vascular states (control, serotonin infusion, histamine in fusion). In addition, we investigated the use of sampling of the raw data t o estimate capillary pressure. Three of the five literature-based estimates of Ppc yielded values similar to Pdo. The optimal (least average differenc e from Pdo) interpolation/extrapolation time points of the curve fits varie d, depending on the type of curve fitting and the state of the pulmonary va sculature. We also determined that a close approximation of Pdo may be deri ved from the raw data, as an alternative to exponential curve fitting.