Abstract
It is possible to separately measure two areas of resistance in the pulmonary circulation: proximal resistance (RP), or the resistance from a point at which pulmonary arterial pressure is measured to the vessels acting as Starling resistors, and distal resistance (RD), or the resistance from the Starling resistor vessels to a point at which pulmonary venous pressure is measured. A model has been set up in the near term fetal goat utilizing a Starling resistor concept of the pulmonary circulation and requires that the circulation to a portion of the left lung be isolated and perfused at a constant flow. Resistance in the different segments are calculated from figures derived in the experimental procedure previously reported in the Fed. Pro. 29:775-6, 1970. Previous work has demonstrated that the drop in resistance which occurs with expansion of the lung and with increased PaO2 occurs in both RP and RD. During hypoxia in the newborn both RP and RD increase. In the unventilated lung bradykinin infusion into the pulmonary artery (60–240 η.g./min.) produced a significant decrease in the RP to 52% of control values, no change in RD, and a decrease in the pressure tending to close the Starling resistor vessles (Ps). In the ventilated lung, there was a significant decrease in the RP (64% of control values) with no changes in either RD or Ps. These data indicate that bradykinin has an immediate and direct effect on the pulmonary vasculature and significantly reduces its resistance to flow. This effect is mediated through the resistance vessels proximal to the area of the Starling resistor.
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Eitzman, D., Gilbert, R., Hessler, J. et al. Effect of bradykinin on the pulmonary vascular resistance in the term fetus. Pediatr Res 5, 427–428 (1971). https://doi.org/10.1203/00006450-197108000-00236
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DOI: https://doi.org/10.1203/00006450-197108000-00236