Hemodynamic control systems are identified during closed-loop operation. Spontaneous fluctuations in instantaneous heart rate and arterial blood pressure are measured continuously during normal sinus rhythm in the conscious dog and during electrically induced atrial fibrillation in the anesthetized dog. A symmetric closed-loop model is identified in which the feedforward path represents the arterial baroreflex and the feedback path represents the lumped mechanical properties of the left ventricle and the arterial system. The direct method of closed-loop identification is implemented with a recursive generalized-least-squares algorithm. The effect of heart rate on blood pressure is identified as a stable, first-order system with a positive gain. The effect of blood pressure on heart rate is identified as a stable, second- or third-order system with a negative gain. The structure of these systems and their estimated time constants, in part, are consistent with a priori knowledge of the input impedance of the aorta and the arterial baroreflex, respectively. Closed-loop identification of dynamic relationships between fluctuating hemodynamic variables thus may provide new, minimally invasive methods for studying hemodynamic control systems.
|Original language||English (US)|
|Number of pages||4|
|State||Published - Jan 1 1986|
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