The Technicon Ektacytometer: automated exploration of erythrocyte function.

The Ektacytometer is a visco-diffractometric method to preferentially examine the functional properties of erythrocytes. The realization of this method in the form of an automated laboratory instrument, the Technicon Ektacytometer, is described. A suspension of RBC is submitted to a uniform shear stress. The resulting deformation of the cells is seen as an elongation of the diffraction image and expressed as the Elongation Index or EI. EI may be traced on an X-Y recorder as a function of stress, time and of suspending medium osmolality. The osmolality is varied automatically in the viscometer and automatically measured via its conductivity, resulting in an "Osmoscan". The Osmoscan is highly reproducible and requires only 150 microliter of blood and 5 minutes per sample. Its high sensitivity to small changes in erythrocyte properties permits the separation of factors affecting RBC deformability, and provides a measure of the osmotic fragility which correlates very well with the traditional test. Other applications are described, including mechanical fragility assays on whole cells, relaxation times of ghosts and the automatic variation of PO2. Possible future applications are suggested.