GAIN-INDUCED OSCILLATIONS IN BLOOD-PRESSURE

''Mayer waves'' are long-period (6 to 12 seconds) oscillations in arte rial blood pressure, which have been observed and studied for more tha n 100 years in the cardiovascular system of humans and other mammals. A mathematical model of the human cardiovascular system is presented, incorporating parameters relevant to the onset of Mayer waves. The mod el is analyzed using methods of Liapunov stability and Hopf bifurcatio n theory. The analysis shows that increase in the gain of the barorefl ex feedback loop controlling venous volume may lead to the onset of os cillations, while changes in the other parameters considered do not af fect stability of the equilibrium state. The results agree with clinic al observations of Mayer waves in human subjects, both in the period o f the oscillations and in the observed age-dependence of Mayer waves. This leads to a proposed explanation of their occurrence, namely that Mayer waves are a gain-induced oscillation.