A practical design equation for accurate quantification of CRRT filter design factors and convection effects

Considering the increasing clinical need for continuous renal replacement therapy (CRRT), further improvement in therapeutic efficacy has become an important focus for researchers. Here, we designed nine CRRT filters with various combinations of hollow fiber packing density (PD) and housing shape (effective hollow fiber length (L) and inner housing diameter (D) ratio (L/D ratio)) to evaluate the clearance of middle molecular uremic toxins (MMs) via simulation of an in vitro continuous veno-venous hemodialysis treatment model. We also used Doppler ultrasonography to measure the maximum internal filtration flow rate (Q_IF-Max) as an aid; this approach facilitated an exploration of the impacts of various design factors on convection effects, while revealing the mechanisms influencing MM removal performance. Furthermore, we constructed a multiple linear regression model of design factors and Q_IF-Max, then conducted experimental verification. Finally, we proposed an accurate and practical design equation to quantify the design factors influencing CRRT filters and convection effects: $$, where N/D² and L/D affect Q_IF-Max by 15.0% and 85.0%, respectively. This design equation was able to effectively quantify the convection effects of CRRT filters with different design factors, thereby predicting MM removal performance; this convenient design equation can support the development of CRRT-related products.