New Aspects on the Mechanism of Autoregulation of Blood Flow
The term autoregulation as used here denotes the ability of an isolated organ to keep the blood flow relatively constant in spite of changes of perfusion pressure. In previous communications pertaining to a system theory analysis of autoregulation (1,2,3,4,5, 6) we reported observations on periodic spontaneous fluctuations of the perfusion flow (v)of isolated rat kidneys, isolated rat hearts, isolated hind limbs and isolated mesentery showing periodicities in the range of 25 sec. (6). These fluctuations which were only observed when the arterial pressure was maintained at values higher than 80–100 mm Hg (i.e. in the range of autoregulation) did not appear as proper sinusoidal oscillations with defined shapes and constant periodicity. Instead, irregular increases and decreases of the flow (v) of varying periodicity were observed (fig.1). A more detailed study of these irregular periodic changes, seemed to promise information on the nature of the underlying pro-cess. Especially so since similar periodicities were previously reported from other circulatory areas and from smooth muscle preparations (3, 7–13). For this purpose we have applied the method of time series analysis consisting in the determination of autocorrelation and power spectral density functions.
KeywordsPerfusion Pressure Power Density Spectrum Pressure Step Power Spectral Density Function Circulatory Area
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