Figure 417

The mass-transfer area coefficient (MTAC). The MTAC represents the clearance rate by diffusion in the absence of ultrafiltration and when the solute accumulation in the dialysis solution is zero [34-39]. MTAC is equal to the product of peritoneal membrane permeability (P) and effective peritoneal membrane surface area (S). Thus, when both capillary blood and dialysate flows are infinite, the clearance rate is directly proportional to the effective peritoneal surface area and inversely proportional to the overall membrane resistance. However, infinite blood and dialysate flows cannot be achieved, and the maximum clearance rate is unattainable. The closest measurable value, the MTAC, was introduced. The MTAC represents an instantaneous clearance without being influenced by ultrafiltration and solute accumulation in the dialysate. The MTAC is measured over a test exchange during which at least two blood and dialysate samples are obtained at different dwell times. The precision of the measurement is enhanced with more data points. The MTAC is seldom used clinically; however, it is a very useful research tool.

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