From the Department of Physiology, Faculty of Medical Sciences, Imam Hossein University, Tehran, Islamic Republic of Iran.
Abstract: (4246 Views)
Effects of acute hypercapnia on the cardiovascular system (CYS) were studied
in the anesthetized cat. After surgery the animal was exposed to a gas mixture of
12% CO2 and 25% O2 in nitrogen, and hypercapnia with low levels of arterial pH
(pHa) was produced for 20 minutes. In the second run the same level of
hypercapnia was induced by ventilating the same cat from the above gas mixture
but pHa was kept normal by a slow and continuous infusion of 1HAM (0.5 mM/
kg/min). Results of this study showed that hypercapnia increased aortic flow and
induced peripheral vasodilation. Hypercapnia produced tachycardia in the
presence of arterial acidosis whereas in its absence this response reversed to
bradycardia. Hypercapnia increased mean arterial blood pressure (Pa) by 20%
during low pHa, whereas this increase was only 10% in the absence of arterial
acidosis. Therefore, it is concluded that hypercapnia in conjunction with arterial
acidosis has a much stronger stimulatory influence on the CYS via different
arterial chemoreceptors.