title: A mathematical model to optimize the drain phase in gravity-based peritoneal dialysis systems.
abstract: Use of patient-specific drain-phase parameters has previously been suggested to improve peritoneal dialysis (PD) adequacy. Improving management of the drain period may also help to minimize intraperitoneal volume (IPV). A typical gravity-based drain profile consists of a relatively constant initial fast-flow period, followed by a transition period and a decaying slow-flow period. That profile was modeled using the equation VD(t) = (V(D0) - Q(MAX) x t) xphi + (V(D0) x e(-alphat)) x (1 - phi), where V(D)(t) is the time-dependent dialysate volume; V(D0), the dialysate volume at the start of the drain; Q(MAX), the maximum drain flow rate; alpha, the exponential drain constant; and phi, the unit step function with respect to the flow transition. We simulated the effects of the assumed patient-specific maximum drain flow (Q(MAX)) and transition volume (psi), and the peritoneal volume percentage when transition occurs,for fixed device-specific drain parameters. Average patient transport parameters were assumed during 5-exchange therapy with 10 L of PD solution. Changes in therapy performance strongly depended on the drain parameters. Comparing 400 mL/85% with 200 mL/65% (Q(MAX/psi), drain time (7.5 min vs. 13.5 min) and IPV (2769 mL vs. 2355 mL) increased when the initial drain flow was low and the transition quick. Ultrafiltration and solute clearances remained relatively similar. Such differences were augmented up to a drain time of 22 minutes and an IPV of more than 3 L when Q(MAX) was 100 mL/min. The ability to model individual drain conditions together with water and solute transport may help to prevent patient discomfort with gravity-based PD. However, it is essential to note that practical difficulties such as displaced catheters and obstructed flow paths cause variability in drain characteristics even for the same patient, limiting the clinical applicability of this model.
authors.affiliation: Renal Division, Baxter Healthcare Corporation, McGaw Park, Illinois 60085, USA. alp_akonur@baxter.com
authors.forename: Alp
authors.initials: A
authors.lastname: Akonur
authors.forename: Ying-Cheng
authors.initials: YC
authors.lastname: Lo
authors.forename: Borut
authors.initials: B
authors.lastname: Cizman
mesh_terms: D001692:Biological Transport; D006112:Gravitation; D006801:Humans; D008962:Models, Theoretical; D010530:Peritoneal Dialysis / Q000379:methods*; D010537:Peritoneum / Q000378:metabolism