Summary
The “mechanical oscillator” technique for the measurement of the density of fluids is based on the influence of mass on the natural frequency of a mechanical oscillator. The practical application of this principle was worked out by Kratky et al. (1969) and Leopold (1970). It is demonstrated in this study that the method permits the continuous high-precision measurement of the density of flowing blood in anesthetized animals. The accuracy is 10−5 g/ml, the maximum sampling rate 20/min.
As found in rabbits and cats during the control state, physiological blood density changes related to spontaneous blood pressure variations are up to 2·10−4 g/ml. The method can be combined with i.v. injections of isotonic and iso-oncotic solutions to determine cardiac output and blood volume on the basis of a “density dilution” principle. Since the density of the interstitial fluid is lower than that of blood, fluid shifts through the capillary walls can be detected. The effects of hypertonic glucose and of hyperoncotic dextran have been examined. Changes in the density of the arterial blood appear within 10 s after i.v. injection of these fluids. Similarly, density changes result from hemorrhage and reinfusion. During and after i.v. administration of vasoactive drugs (noradrenaline, angiotensin II, acetylcholine), marked transient changes in blood density are seen which obviously reflect the effects of fluid shifts through the capillary walls. During hemorrhagic hypotension we found periodic variations in the blood density synchronous with spontaneously occurring Mayer waves. The new method seems to be a promising tool for investigations on physiological and pathological capillary fluid dynamics.
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References
Altmann, Ph. L., Dittmer, D. S.: Respiration and Circulation. Biological Handbooks. Bethesda, Md.: FASEB (1970)
Gaziùta, S., Scott, J. B., Swindall, B., Haddy, J. F.: Resistance responses to local changes in plasma osmolality in three vascular beds. Am. J. Physiol.220, 384–391 (1971)
Grega, G. J., Haddy, F. J.: Forelimb transcapillary fluid fluxes and vascular resistances in catecholamine shock. Am. J. Physiol.220, 1448–1462 (1971)
Haddy, F. J., Scott, J. B., Grega, G. J.: Peripheral circulation: fluid transfer across the microvascular membrane. In: Cardiovascular Physiology II (A. C. Guyton, A. W. Cowley, eds.) Baltimore, London, Toronto: University Parks Press (1976)
Järhult, J.: Osmolar control of the circulation in hemorrhagic hypotension. Acta Physiol. Scand., Suppl.423 (1976)
Kaiser, A. S., Diana, J. N.: Effect of angiotensin and norepinephrine on capillary pressure and filtration coefficient in isolated dog hindlimb. Microvasc. Res.7, 207–228 (1974)
Kratky, O., Leopold, H., Stabinger, H.: Dichtemessung an Flüssigkeiten und Gasen auf 10−6 g/cm3 bei 0.6 cm3 Präparatvolumen. Z. angew. Physik.27, 273–277 (1969)
Kratky, O., Leopold, H., Stabinger, H.: The determination of the partial specific volume of proteins by the mechanical oscillator technique. In Methods in Enzymology (Hirs and Timasheff, eds.) Vol. XXVII Part D. New York: Academic Press (1973)
Leopold, H.: Die digitale Messung der Dichte von Flüssigkeiten. Elektronik,19, 297–302 (1970)
Mellander, S., Johansson, B.: Control of resistance, exchange and capacitance functions in the peripheral circulation. Pharmacol. Rev.20, 117–196 (1968)
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Kenner, T., Leopold, H. & Hinghofer-Szalkay, H. The continuous high-precision measurement of the density of flowing blood. Pflugers Arch. 370, 25–29 (1977). https://doi.org/10.1007/BF00707941
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DOI: https://doi.org/10.1007/BF00707941