IMPROVEMENTS IN CALCULATION OF RENAL RESISTANCE TO BLOOD FLOW. CHARTS FOR OSMOTIC PRESSURE AND VISCOSITY OF BLOOD

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Abstract
The similarity between blood flow and the flow of plastic solids, as described by Bingham, is used to substitute a variable in place of a static value for the yield pressure in the application of Poiseuille''s Law to the kidney. An expression for post-arteriolar resistance (defined precisely) is added to those for arteriolar resistance so that total renal resistance to blood flow can be computed, if desired. A method is elaborated by which serum protein of any albumin-globulin ratio can be quickly converted by means of a formula or published chart into an osmotically equivalent conc. of serum protein of A:G ratio 2.20. A 2d chart then provides the systemic osmotic pressure of blood (or plasma) for the osmotically equivalent conc. of standard serum protein and also the osmotic pressure of the blood concentrated in the glomerulus by ultrafiltration to the degree indicated by the inulin-to-diodrast clearance ratio. These 2 values simplify and improve the calculation of renal resistance to blood flow. A chart for blood viscosity, as affected by the serum protein conc. and the hematocrit, permits the ready calculation of renal resistance with allowance for the viscosity of the sub- ject''s blood. While the charts for osmotic pressure and viscosity of blood have been designed primarily to aid in studying renal function, they have wider applicability wherever blood viscosity and osmotic pressure are required without direct measurement.