Effect of aortic balloon inflation on ventilation and brain stem blood flow in piglets.
Increases in brain stem blood flow (BBF) during hypoxia may decrease tissue PCO2/[H+], causing minute ventilation (VE) to decrease. To determine whether an increase in BBF, isolated from changes in arterial PO2 and PCO2, can affect respiration, we obstructed the thoracic aorta with a balloon in 31 intact and 24 peripherally chemobarodenervated, anesthetized, spontaneously breathing newborn piglets. Continuous measurements of cardiorespiratory variables were made before and during 2 min of aortic obstruction. Radiolabeled microspheres were used to measure BBF before and approximately 30 s after balloon inflation in eight intact and five denervated animals. After balloon inflation, there was a rapid increase in mean blood pressure in both the intact and denervated animals, followed within 10 s by a decrease in tidal volume and VE. In the intact animals, the decrease in VE after acute hypertension can be ascribed to a baroreceptor-mediated reflex. After peripheral chemobarodenervation, however, acute hypertension continued to produce a decrease in VE, which cannot be explained by baroreceptor stimulation. In these denervated animals, aortic balloon inflation was associated with an increase in BBF (13.1 +/- 2.7%; P less than 0.05). We speculate that the increase in BBF during hypoxia may contribute to the decrease in ventilation observed after carotid body denervation.
Green
G A
GA
Department of Pediatrics, University of Virginia School of Medicine, Charlottesville 22908.
Darnall
R A
RA
Bierd
T B
TB
Adams
J M
JM
D000818:Animals; D000831:Animals, Newborn; D001011:Aorta / Q000502:physiology*; D001639:Bicarbonates / Q000097:blood; D001794:Blood Pressure; D001933:Brain Stem / Q000098:blood supply*; D002245:Carbon Dioxide / Q000097:blood; D003714:Denervation; D004195:Disease Models, Animal; D006339:Heart Rate; D000860:Hypoxia / Q000503:physiopathology*; D010313:Partial Pressure; D011311:Pressoreceptors / Q000502:physiology; D012016:Reference Values; D012039:Regional Blood Flow; D012119:Respiration; D013116:Spinal Cord / Q000502:physiology; D013552:Swine
D001639:Bicarbonates; D002245:Carbon Dioxide