血液透析濾過器における新規な解析モデルとその応用 New Analytical Model and its Applications for Hemodiafilter

血液透析濾過器について，既報の実験データにより十分検証した新規の解析モデルを提案する．当解析モデルでは，溶質の膜透過式の対流項にZydney（1993）の提唱式を，血液側境膜物質移動には修正したRautenbach and Albrecht（1989）式を，透析液側境膜物質移動にはFukuda et al.（1992）式を，また血液および透析液の流動圧損式には重力項を付与したHagen-poiseuille式を適用した．この解析モデルを使って，血液透析濾過器性能への中空糸形状の影響について検討したところ次の結果を得た．小分子量溶質のクリアランス値は中空糸形状の影響を中分子量溶質の場合より強く受ける．すなわち，等膜面積下では中空糸が小径で中空糸長が長いほど中空糸内の血液流速が速くなり大きな値をとる．一方，中分子量溶質では，クリアランス値は中空糸形状には余り依らず，除水量の影響が大であることが明らかとなった．

A new analytical model for predicting the mass transport characteristics in hemodiafiltration was presented, which was consistent with in vitro measurements reported by earlier researchers.In this model, Zydneys equation (1993), modified Rautenbachs equation (1989) and Fukudas equation (1992) were used for convective solute transport, and for boundary-layer solute transport on the blood side and the dialysate side, respectively, and the Poiseuille equation was added as a gravity effect term because of vertical setting of the hemodiafilter.The model was applied to study the influence of hollow fiber membrane geometry on the performance of hemodiafilter, and it was found that the clearance of low molecular weight solute depends on fiber geometry more strongly than that of medium molecular weight solute. That is, for a given membrane surface area, the smaller the diameter of the hollow fiber is, the longer is its length and the faster is the blood flow velocity, resulting in larger clearance of low molecular weight solute.On the other hand, the clearance of medium molecular weight solute depend hardly on fiber geometry, but greatly on ultrafiltration flow rate.