The International Journal of Artificial Organs

Proportional integral feedback control of ultrafiltration rate in hemodialysis

Sabrina Casper, Doris Fuertinger, Leticia M Tapia Silva, Lemuel Rivera Fuentes, Stephan Thijssen, Peter Kotanko


Background: Most hemodialysis patients without residual kidney function accumulate fluid between dialysis session that needs to be removed by ultrafiltration. Ultrafiltration usually results in a decline in relative blood volume (RBV). Recent epidemiological research has identified RBV ranges that were associated with significantly better survival. The objective of this work was to develop an ultrafiltration controller to steer a patient's RBV trajectory into these favorable RBV ranges.

Methods: We designed a proportional-integral feedback ultrafiltration controller that utilizes signals from a device that reports RBV. The control goal is to attain the RBV trajectory associated with improved patient survival. Additional constraints such as upper and lower bounds of ultrafiltration volume and rate were realized. The controller was evaluated in in silico and ex vivo bench experiments, and in a clinical proof-of-concept study in two maintenance dialysis patients.

Results: In all tests, the ultrafiltration controller performed as expected. In the in silico and ex vivo bench experiments, the controller showed robust reaction toward deliberate disruptive interventions (e.g. signal noise; extreme plasma refill rates). No adverse events were observed in the clinical study.

Conclusions: The ultrafiltration controller can steer RBV trajectories toward desired RBV ranges while obeying to a set of constraints. Prospective studies in hemodialysis patients with diverse clinical characteristics are warranted to further explore the controllers impact on intradialytic hemodynamic stability, quality of life, and long-term outcomes.

Keywords: Automated feedback system; artificial kidney; closed-loop controller; hemodialysis; relative blood volume; ultrafiltration rate feedback control.


About the Author

Stephan Thijssen, MD

Vice President, Applied and Basic Research

Prior to coming to New York, Stephan worked in the Nephrology Department at the University Hospital Homburg, Germany. He joined RRI in 2005. Stephan brings more than one and a half decades of research experience to the RRI team, covering laboratory research, clinical research, epidemiology research, and mathematical modeling. He has written and published an extensive number of scholarly articles in leading national and international peer-reviewed scientific journals and published several book chapters. 

Dr. Peter Kotanko, MD

RRI Research Director

SVP, Corporate Research & Development

Peter Kotanko, MD, is Research Director at the Renal Research Institute (RRI), New York. Prior to joining RRI, from 1997 to 2007 he served as vice chair of a department of internal medicine at an academic teaching hospital in Graz, Austria. Prior to moving to Graz in 1989, he worked from 1982 to 1989 in the Department of Physiology and the University Clinic of Internal Medicine in Innsbruck, Austria. From 1995 to 1996 he trained in nephrology at the Hammersmith Hospital, London, United Kingdom.