Identification of major slow blood pressure oscillations in conscious dogs

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Abstract
All physiological feedback systems (e.g., in arterial pressure control) tend to oscillate in a characteristic manner. Mechanoreceptors can effectively buffer resulting fluctuations in arterial blood pressure. In this study arterial and cardiopulmonary receptors were interrupted in eight conscious foxhounds by sectioning the afferent pathways to the central nervous system. In response, three major peaks were detected in the blood pressure power spectrum: in addition to the well-known rhythms reflecting heart rate and respiration, very slow oscillating waves with a cycle length to 20 .+-. 4 min and a 105-fold higher power than the other two waves were detected. The amplitude of these oscillations could exceed 100 mm Hg. This peak was also identified under control conditions (at a cycle length of 21 .+-. 4 min, n = 6); however, the relative power was > 103-fold less with mechanoreceptors intact (P < 0.001). Thus a major slow oscillating component of arterial pressure control has been identified. Normally, mechanoreceptors buffer the resulting waves of this oscillator. These very strong fluctuations may characterize an important feature of blood pressure regulation.