AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 5 1004-R1011, Copyright © 1989 by American Physiological Society
Influence of lung inflation reflex on vascular capacitance in the systemic circulation
E. Y. Cheng, J. Kay, S. Hoka, Z. J. Bosnjak, R. L. Coon, J. L. Seagard and J. P. Kampine
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, 53226.
The effects of sustained lung inflation on systemic vascular capacitance
(SVC), systemic vascular resistance (SVR), and cardiac sympathetic efferent
nerve activity (SENA) were investigated in anesthetized dogs. By use of a
total cardiopulmonary bypass, the lungs were inflated to tracheal pressures
of 10, 15, and 20 mmHg. Tracheal pressures of 10, 15, and 20 mmHg increased
system vascular capacitance by 1.4, 3.1, and 4.3 ml/kg and decreased
systemic vascular resistance by 0.11, 0.15, and 0.16 mmHg.kg.min-ml-1,
respectively, at low carotid sinus pressure (CSP) of 41 mmHg. SENA showed a
concomitant decrease. Bilateral vagotomy attenuated the change in SVR by
69%, SVC by 62%, and SENA by 97% when lungs were inflated to a tracheal
pressure of 20 mmHg at a low CSP. These results indicate that lung
inflation causes a reflex induced increase in SVC as well as a decrease in
both SVR and SENA. The lung inflation reflex is mediated primarily through
vagal afferent nerve fibers with a small contribution from other afferent
nerve pathways.
