Quantitative analysis of the Landis method

Abstract

Landis developed the single capillary micro-occlusion method for the determination of the capillary filtration coefficient, Lp. More recently, several modified versions of Landis's original procedure have been introduced in an attempt to measure Lp with greater ease and accuracy. Each of the techniques assumes that the capillary is a uniformly cylindrical indistensible tube. Since recently obtained experimental data have demonstrated that the capillary is compliant, a distributed mathematical model of the capillary was developed to reveal the extent to which capillary distensibility influences the measurement of Lp at different sites along the capillary. After assigning physiologic values to this modeled capillary, including Lp and the capillary wall's modulus of elasticity, Landis's method and two of its modified versions were performed on the modeled capillary, with each yielding values for Lp at 10 different locations along the capillary. Comparison of these 10 computed Lp values with the corresponding Lp values defined in the modeled capillary demonstrates that capillary distensibility can introduce significant error into the measurement of Lp.