Analysis of Diffusion Limitations on a Catheter Imbedded in Body Tissues
Accurate in vivo measurement of dissolved gases in body fluids and tissues has been a goal of biomedical research for many years. Until recently this search had been attended with relatively little success. Recently, however, Folkman and co-workers (1967) demonstrated that a catheter made of Medical Silastic could measure dissolved blood gases in vivo. Unfortunately, the size of the catheter required surgical insertion. Ernst and O’Steen (1970) developed a catheter of the same material which could be inserted through a 14 gauge hypodermic needle, and they showed that it could be used for in vivo monitoring of blood gases. These investigators also reported measurements taken after insertion into the peritoneal cavity of a dog and one of their observations of particular interest was that the partial pressure of oxygen in the peritoneal cavity declined from 110 mm Hg to 7 mm in 5 minutes when the dog was changed from breathing air to breathing pure nitrogen. It is of interest to inquire as to how much of the time lag they observed was due to equilibration in the tissues and how much was due to the mass transfer resistance of the catheter wall.
KeywordsPeritoneal Cavity Fiber Bundle Catheter Lumen Blood Perfusion Rate Artificial Internal Organ
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