STARLING RESISTOR VS, DISTENSIBLE VESSEL MODELS FOR EMBOLIC PULMONARY-HYPERTENSION

We investigated whether the Starling resistor model (Mitzner et al. J. Appl. Physiol. 51: 1065-1071, 1981) or a distensible vessel model (Ha worth et al. J. Appl. Physiol. 70: 15-26, 1998) best describes pulmona ry vascular pressure-flow (Q) relationships in embolic pulmonary hyper tension. Mean pulmonary arterial pressure (P-pa)-Q plots at constant l eft atrial pressure (P-la) and P-pa-P-la plots at constant Q were inve stigated in seven dogs before and after 500-mu m glass bead pulmonary embolism. Embolization to a mean angiographic obstruction of 78% incre ased the slope and extrapolated pressure intercept (P-i) of P-pa-Q plo ts and increased the inflection point of P-pa-P-la plots, above which an increase in P-la is transmitted to P-pa in a ratio of similar to 1: 1. The Starling resistor and the distensible vessel model provided a r easonably good fit to the P-pa-Q and P-pa-P-la coordinates before and after embolism. However, contrary to the prediction of the Starling re sistor model, no correlation was found between the inflection point of P-pa-P-la plots and P-i. We therefore conclude that an increased clos ing pressure is unlikely to contribute to embolic pulmonary hypertensi on.