PARTIAL STREAM SAMPLING ASSUMPTION IN INTESTINAL PERFUSION STUDIES

During the past several years, the technique of in vivo intestinal perfusion with partial stream sampling has been increasingly widely used to gather information on intestinal absorptive processes in man. The basic technique involves infusion of test solution through a proximal opening; and aspiration of samples through one or more distal openings a fixed distance apart. Samples are analyzed for test solute concentrations; from such sample data, conclusions are drawn concerning alterations in stream concentrations between the sampling sites. An underlying assumption for the validity of such a method is: that sample concentrations are the same as average stream concentrations. This assumption has not previously been precisely stated. A precise statement of it is given here, together with an analytic proof of conditions necessary and sufficient for its validity. A brief verbal comment is included to clarify the practical meaning of the analytic statement. © 1968 N. Rashevsky.