Gastrointestinal transit time: An in vitro study of parameters controlling the mean relative residence times of particles in a laminar fluid flowin

Abstract

Several factors which may influence gastrointestinal residence time have been studied in vitro. The relative mean residence time tp/t0, where tp is the mean residence time of the particles and t0 is the mean residence time of the fluid, has been determined for barium sulphate, bismuth subcarbonate, talc, magnesium carbonate, kaolin and latex particles in a horizontal tube. Dimensional analysis leads to the following relationship: tp/t0 = f (dp2gΔρ{variant}/μ ν = f (Re/Fr), where dp is the particle diameter, g is the acceleration due to gravitation, Δρ{variant} is the density difference between particles and fluid, μ is the fluid viscosity and ν is the average flow velocity. The ratio Re/Fr may be interpreted as the ratio of the gravitational force Fg to the drag force Fd on a particle. The experimental results showed that the ratio Re/Fr is a good correlating group and that in the range of Re/Fr from 0 to 400, tp/t0 increases rapidly with increasing Re/Fr. At large Re/Fr values, tp/t0 remains almost constant. From the dependency of tp/t0 on Re/Fr, it is concluded that while Δρ{variant} can have a significant effect on tp/t0, this effect can be compensated for by a change in the viscosity of the fluid. © 1988.