UNILATERAL HYPOXIC PULMONARY VASOCONSTRICTION IN THE DOG, PONY AND MINIATURE SWINE

The hypoxic pulmonary vasoconstrictor response to unilateral hypoxia was analyzed in pentobarbital anesthetized dogs (n = 5), miniature swine (n = 5), and ponies (n = 5). The left and right lungs (LL, RL) were separately ventilated with the LL exposed to inspired oxygen concentrations (CI(O2)) of 100%, 12%, 8% or 4%, while the RL always received a CI(O2) = 100%. Pulmonary blood flow distribution was measured using 15-mu-m radioactive microspheres. LL PA(O2), and percent pulmonary blood flow diversion (%FD) were calculated at each CI(O2). At CI(O2) of 4% there were significant differences (P greater-than-or-equal-to 0.05) between the %FD responses of each species (mean +/- S.E): the %FD(swine) (95.1 +/- 1.3) > %FD(pony) (76.0 +/- 4.6) > %FD(dog) (50.1 +/- 9.4). For all species, the %FD was inversely related to the level of regional hypoxia, but there were marked species differences in the magnitude and sensitivity of hypoxic pulmonary vasoconstriction with the swine being the strongest responder, the pony intermediate, and the dog the weakest responder.