Comparison of Human Erythrocyte Filterability with Trapping Rate Obtained by Nickel Mesh Filtration Technique: Two Independent Parameters of Erythrocyte Deformability

Background: Erythrocyte deformability is a major determinant of microcirculation in vivo. Although this concept was defined as filterability evaluated by flow-pressure curve constructed during a filtration process of erythrocyte suspension through a nickel mesh filter, the behaviours of erythrocytes during the filtration process are unknown.

Aim: The present study aimed to obtain the better rheological understanding of the behaviours of erythrocytes passing through the nickel mesh filter.

Methods: Blood sample was obtained from 8 apparently healthy subjects after obtaining informed consent. Erythrocyte filterability (%) was calculated as the flow rate of a hematocrit-adjusted erythrocyte suspension relative to that of saline at a filtration pressure of 100 mmH2O in flow-pressure curves obtained by nickel mesh filtration technique. Nickel mesh filters showing specific pore sizes of 6.00 μm (step 1) and 5.31 μm (step 2) were chosen, and two-step filtration protocol was performed. Erythrocytes counts (EC) were performed immediately before (ECpre) and after (ECpost) each filtration, and erythrocyte trapping rate (%) was defined as (ECpre – ECpost) / ECpre. Erythrocyte filterability and trapping rate were correlated in each step for data analysis.

Results: ECpre was always greater than corresponding ECpost in every subject and in both steps. Erythrocyte filterability in the step 1 (91.8 ± 2.1%) was close to that in the step 2 (90.0 ± 10.3%). Likely, the trapping rate in the step 1 (77.8 ± 2.4%) was close to that in the step 2 (79.4 ± 7.0%). Mean filterability in step 1 did not differ from that in step 2 (p = 0.637), and the same was true with respect to the mean trapping rate (p = 0.516). However, individual comparison between the filterability and the trapping rate of both steps demonstrated no correlation.

Conclusions: The present findings indicate that erythrocytes in suspension are trapped substantially by our nickel mesh filter. This trapping rate was not correlated to the erythrocyte filterability obtained by the flow-pressure curve during the nickel mesh filtration. Therefore, the erythrocyte trapping rate should be considered as a hemorheological parameter independent of the erythrocyte filterability.