The ratio f describes the relationship between the whole body hematocrit and the venous hematocrit (see 02.10.05). The whole body hematocrit can be used to calculate a patient's whole body red cell mass (RCM). Balga et al evaluated the impact of various values of f on the calculated RCM. The authors are University Hospital in Bern, Switzerland.


f =

= (whole body hematocrit) / (venous hematocrit)


Subjects for study: males from 7.9 to 88.4 and females from 15.5 to 80.5 years of age

Values of f



low end of range






high end of range




The mean value for men and women was 0.911


calculated red cell volume in liters =

= (f ratio) * (venous hematocrit) * (plasma volume in L) / (1 - ((f ratio) * (venous hematocrit)))


The plasma volume can be measured after intravenous infusion of 125I-labelled albumin.


total blood volume in liters =

= (plasma volume) + (red cell volume in liters)


To calculate the red cell mass (RCM) the density of erythrocytes is multiplied by the red blood cell volume.


density of whole blood: 1.055

density of plasma: 1.027

demsity of erythrocytes 1.096


On page 27 the authors reference an f value of 0.864. If this is multiplied by the density of whole blood (1.055) then the value of 0.911 is returned, which is the mean value for f.


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