Dynamic response of local pulmonary blood flow to alveolar gas tensions: experiment.
The purpose of this study was to investigate the mechanism that causes a damped oscillatory response of local pulmonary blood flow to local hypoxia. The left lower lobe (LLL) of 10 anesthetized dogs was ventilated independently but synchronously with the rest of the lungs. Blood flow to the LLL as a proportion of total flow (QLLL/QT) was measured during the on-transient of the hypoxic response when LLL inspirate was changed from O2 to N2. There was a damped oscillatory response of QLLL/QT to hypoxia (34 of 40 trials). In contrast, the off-transient was always monotonic. There was no enhancement of the steady state or dynamic hypoxic response with repeated challenges. Local alveolar hypercapnia caused a damped oscillatory response in the presence of local hypoxia (15 of 20 trials), but there was no response in the presence of local hyperoxia. We conclude that 1) the dynamic pulmonary vascular response to O2 and CO2 are not additive because the response to CO2 is attenuated by hyperoxia and 2) the damped oscillatory response that occurs during hypoxia is the result of changes of local alveolar CO2 per se.
Paradowski
L J
LJ
Department of Medicine, State University of New York, Buffalo 14215.
Grant
B J
BJ
D000818:Animals; D004285:Dogs; D000860:Hypoxia / Q000503:physiopathology*; D008168:Lung / Q000098:blood supply*; D010100:Oxygen / Q000494:pharmacology*; D011652:Pulmonary Circulation / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*
D010100:Oxygen