Abhandlungen zur Mechanik der Flüssigkeiten

Müller, Aloys

doi:10.1007/bf02119188

Archiv für Kreislaufforschung

1939

DOI: 10.1007/bf02119188

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Abhandlungen zur Mechanik der Flüssigkeiten

Aloys Müller

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Cited by 8 publications

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“…It is evi-dent that at any given c, /r is considerably lower in the case of mammalian blood. Thus, Miiller (10) found that rubber discs of axis ratio (thickness/ diameter) = 0.18 in aqueous glycerol would only flow with great difficulty at 30% concentration in a rigid tube 5 times the diameter of the discs. Even at c = 0.8, the relative viscosity of the dog's blood shown in Fig.…”

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confidence: 99%

The Microrheology of Red Blood Cell Suspensions

Goldsmith

1968

The Journal of General Physiology

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The general problem of microrheology is to predict the macroscopic flow properties of a material from a detailed description of the behavior of its constituent elements. This approach has been used to study suspensions of human red cells in plasma or Ringer's solution flowing steadily in rigid tubes 8-25 times the red cell diameter by observing individual cell motions under the microscope. The results have been compared with those previously obtained with model particles under similar conditions. In very dilute suspensions single red cells rotated in orbits similar to those of rigid discs at low flow rates, but, in common with model deformable particles, were observed to migrate away from the tube wall. Linear rouleaux of red cells rotated as rodlike particles and were flexible, bending during their rotational orbits in a manner similar to that of filaments of nylon or Dacron. Transparent concentrated suspensions were produced by preparing ghost cells reconstituted in biconcave form in plasma. In these, the motions of some unhemolyzed red cells were followed. The erythrocyte velocity profiles were blunted at concentrations above 20 %; the cell paths were erratic because of frequent radial displacements, especially at the tube periphery, with the particles being markedly deformed and oriented parallel to the flow. Finally, the difference in flow pattern in large and small vessels is discussed and some relevant model experiments are described.To the rheologist, vertebrate blood is a very concentrated suspension of deformable, disclike particles which circulates in distensible vessels whose sizes range from less than 1 to 3000 red cell diameters. As shown by measurements of the viscosity, blood possesses a remarkable fluidity when compared to other model particle suspensions of spheres and discs. This appears to be due in large measure to the deformability of the red cell, which has been seen to change shape during flow in the capillaries (1, 2) and, as described below, to deform also in large vessels owing to collisions with neighboring particles (3). Fig. 1 compares the relative viscosity, -, (viscosity of suspension/viscosity of pure suspending phase), of a number of model dispersions with that of blood as a function of the volume concentration, c, of suspended particles. It is evi-5 s

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confidence: 99%

The Microrheology of Red Blood Cell Suspensions

Goldsmith

1968

The Journal of General Physiology

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Die plasmatische Infiltration der Aortenwand

Jipp

1964

Klin Wochenschr

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Influence of catheter position on blood pressure values in the pulmonary artery of the dog

et al. 1973

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In measuring pulmonary arterial pressure with special catheters in 19 dogs, anesthetized with morphine-urethane, mean pressure differences of 2.2 _ 0.7 (.~---Sx) mmHg (= 9 ~ of lateral pressure) were obtained between lateral pressure and total pressure at normal flow rates, and of 9.1 _+2.7 mmHg (= 19~/0 of lateral pressure) at maximal flow rates. The transition from laminar to turbulent flow alters the relation between catheter measured kinetic energy and kinetic energy calculated by electromagnetically measured flow. There was, however, nosignificant difference between lateral pressure and downstream pressure for V~VK and ~" ~ VK. This is incompatible with Burton's statement to the effect that downstream pressure is significantly lower than lateral pressure, and that this fact results in serious consequences for calculation and interpretation of pulmonary vascular resistance and distensibility of the pulmonary vascular bed. In experiments on models, local turbulences at the catheter opening pointing d~wnstream could be demonstrated and are believed to cause this phenomenon.Blood pressure measurement in the heart and main vessels by means of catheters is now a routine procedure in cardiology. Catheterization of the right heart and puhnonary artery, in particular, is usually performed without undue technical difficulties and is of great importance for the diagnosis of cardiac valvular lesions and the estimation of pulmonary vascular resistance. Therefore it is reasonable to investigate the reliability of blood pressure measurements obtained in this way.Pressure is static energy per unit volume, as represented by the side pressure in a vessel (= lateral pressure). Depending upon the catheter position in a fluid, the measured pressure values can be expected to differ from the true lateral pressure. Burton (1969) states that measuring pulmonary artery pressure in the usual way as downstream pressure results in an error of up to 52 % of true lateral pressure. If this is true, all conclusions based on conventional pressure measurement would be misleading.The discrepancy between current teaching (which assumes considerable distensibility of the pulmonary vascular bed, Carlill et al. 1967, Wagner 1929, Wezler 1953, Williams 1954 and Burton's statement initiated our systematic investigations on the hydrodynamic model and on animals described in this paper. *) Supported by the Deutsche Forschungsgemeinschaft

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Abhandlungen zur Mechanik der Flüssigkeiten

Cited by 8 publications

References 9 publications

The Microrheology of Red Blood Cell Suspensions

The Microrheology of Red Blood Cell Suspensions

Die plasmatische Infiltration der Aortenwand

Influence of catheter position on blood pressure values in the pulmonary artery of the dog

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