Potentiation of Lobar Hypoxic Pulmonary Vasoconstriction by Intermittent Hypoxia in Dogs

Publisher Website
Google Scholar
Abstract
The hypothesis that lobar hypoxic pulmonary vasoconstriction (HPV) would be potentiated by repeated vasoconstriction (HPV) challenges was studied. In 16 open-chested pentobarbital-anesthetized dogs, repetitive selective hypoxia of the left lower lobe (LLL) (group I = LLL N ventilation, n = 8; group II = LLL absorption atelectasis, n = 8) caused the percentage decrease in the electromagnetically measured fraction of the cardiac output perfusing the LLL (.ovrhdot.QLLL/.ovrhdot.Qt) to become progressively greater (increased LLL HPV) through the first 3 hypoxic challenges in group I and through the first 4 hypoxic challenges in group II. In 4 dogs in each group, after 8 sequential hypoxic challenges with the initial standard method were performed, the alternative method was performed 3 times. There was no significant difference between the 8th LLL HPV response and the subsequent three. The mechanism of blood flow decrease to atelectatic lung is probably the same as for N-ventilated lung, namely, by HPV. To maximize HPV in the nonventilated lung during one lung ventilation, several repeated intermittent cycles of deflation-inflation to the lung should be performed during the initiation of one lung ventilation.