Sinoaortic deafferentation reduces intrapulmonary shunt in dogs with oleic acid lung injury

Hypoxic stimulation of the peripheral chemoreceptors has been reported to inhibit hypoxic pulmonary vasoconstriction. To evaluate the pathophysiological importance of this observation, we investigated the effects of surgical peripheral chemoreceptor denervation on pulmonary vascular tone and gas exchange in 17 pentobarbital-anesthetized dogs with oleic acid pulmonary edema. Pulmonary arterial pressure-cardiac index (Ppa/Q) plots, blood gases, and intrapulmonary shunt measured by the SF6 method were obtained at base line, after peripheral chemodenervation (n = 9) or after sham operation (n = 8), and again after 0.09 ml.kg-1 intravenous oleic acid. Over the range of Q studied (2-5 l.min-1.m-2), Ppa/Q plots were best fitted as first-order polynomials in most dogs in all experimental conditions. Chemoreceptor denervation increased Ppa at the lowest Q, while sham operation did not affect the Ppa/Q plots. Oleic acid increased Ppa over the entire range of Q and increased intrapulmonary shunt. This latter was measured at identical Q during the construction of the Ppa/Q plots. Chemoreceptor-denervated dogs, compared with sham-operated dogs, had the same pulmonary hypertension but lower intrapulmonary shunt (36 +/- 4 vs. 48 +/- 5%, means +/- SE, P less than 0.04) and venous admixture (43 +/- 4 vs. 54 +/- 3%, P less than 0.02). We conclude that in intact dogs chemoreceptor denervation attenuates the rise in intrapulmonary shunt after oleic acid lung injury. Whether this improvement in gas exchange is related to an enhanced hypoxic pulmonary vasoconstriction is uncertain.