Preprint / Version 1

Real-Time Expert-System Identification of Blood Pressure Measurement Accuracy During Renal Dialysis Treatment


  • Paul Stewart University of Cumbria
  • Jill Stewart University of Cumbria U.K.
  • Rebecca Noble University of Nottingham UK
  • Daniela Viramontes-Horner University of Nottingham UK
  • Maarten Taal University of Nottingham UK
  • Nicholas Selby University of Nottingham UK



real-time, measurement accuracy, hypotension, expert system, dialysis, blood pressure measurement


Abstract — Objective: Current practice relies on intermit- tent occluding arm cuff measurements to monitor blood pressure during hemodialysis and to detect hypotension. However, systematic reviews report measurement accuracy challenges associated with brachial cuff measurements observed in the general population, and the factors con- tributing to inaccuracy are likely to be accentuated during dialysis treatment. There is currently no formal process to identify unreliable cuff BP measurements, and staff gen- erally rely on ad hoc extra measurements and averaging readings. The objective of the activity described in this paper was to design a computational method to identify unreliable cuff measurements as they are taken and thus provide decision support to practitioners on dialysis units. Reliable intermittent systolic measurements are fundamen- tally important to both the calibration of continuous blood pressure measurements, and methodologies to predict the onset of hypotension.

Methods: Patient studies with concurrent measurements of real-time continuous dialysis line pressure and intermit- tent systolic brachial cuff pressure during typically 4-hour, dialysis treatment sessions, revealed that some cuff mea- surements lay outside the prediction bounds associated with the expected quasi-linear (time-varying) relationship between arterial line and brachial pressure measurements. An AI expert system was designed, which embodies the mathematical relationships predicted by a system model, and a further complex rule-set which is able to discriminate between reliable and unreliable cuff measurements in real time based on sparse intermittent incoming data. The de- veloped system was deployed on an observational patient study during hemodialysis treatments, outputting recom- mendations and justifications for accepting/rejecting cuff measurements. The accepted measurements were fed into a continuous, non-invasive systolic pressure estimator as calibration, enabling the reliability of the decisions made in the arterial line / systolic pressure domain to be verified in the systolic pressure / time domain. Results: Data collected from a prospective, observational patient study exhibited robust identification of unreliable arm cuff measurements, with the system operating as decision support. Continuous, non invasive, SBP predictions exhibited enhanced accu- racy, in a typical example case, reducing mean error from 16.7mmHg to 6.8mmHg

Conclusion: A hybrid hardware/software system has been designed which utilises non-invasive continuous measurement of arterial dialysis line pressure to improve intermittent arm cuff measurements in order by identifying unreliable arm cuff measurements. The expert system com- putational core showed robust operation in accepting or excluding incoming arm cuff measurements. The devised system can support two requirements in future applica- tions. Firstly, offering a repeatable and robust methodology to identify unreliable arm cuff measurements. Secondly to support the development of reliable SBP prediction algo- rithms to enable early intervention to predict hypotensive episodes and enable early intervention to prevent intradia- lytic hypotension.

Abbreviations: cardiovascular disease (CVD); end-stage kidney disease (EKD); intradialytic hypotension (IDH); blood pressure (BP), systolic blood pressure (SBP), di- astolic blood pressure (DBP), Hemodialysis (HD), expert system (ES)

Index Terms—blood pressure measurement, dialysis, expert system, hypotension, measurement accuracy, real- time


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Author Biographies

Paul Stewart, University of Cumbria

Paul G. Stewart Received the BEng (1996) and PhD (2000) degrees in electronic, control and systems engineering from the Department of Automatic Control, University of Sheffield, U.K. and has held posts of Head of Aerospace Engi- neering at Salford University, Founding Head of Engineering and Pro Vice Chancellor Research at Lincoln University, Director of Institute for Sustainable Engineering and the Mel Morris En- dowed Chair in Intelligent Systems at the Univer- sity of Derby, and Founding Research Chair in

Engineering and Advanced Manufacturing at the University of Cumbria. Professor Stewart is Deputy Editor in Chief of Energies Journal, a Fellow of the Higher Education Academy U.K., Senior Member of the Institution of Electronic and Electrical Engineering (Chairman: UK and Republic of Ireland IEEE Industrial Electronics Chapter (2009 – 2010)), Fellow of the Institution of Mechanical Engineers, and a Chartered Engineer.

Jill Stewart, University of Cumbria U.K.

Jill Stewart received an MEng (2001) and PhD (2005) in mechanical engineering from the Wolf- son School of Mechanical Engineering at the University of Loughborough UK. Since then she has held a number of academic posts including Head of School /Department at Lincoln Univer- sity and Sheffield Hallam University. She is the founding Director of the Institute of Engineering, Computing and Advanced Manufacture at the University of Cumbria. Professor Jill is a Fellow of the HIgher Education Academy, a Fellow of

the Institution of Mechanical Engineering and a Chartered Engineer.

Rebecca Noble, University of Nottingham UK

Rebecca Noble is a research fellow in the Cen- tre for Kidney Research and Innovation (CKRi) in Royal Derby Hospital as a research fellow, pre- viously in the Precision Imaging Beacon at the University of Nottingham. She graduated from The University of Nottingham receiving a Bach- elor of Medicine Bachelor of Surgery (2012) and BMedSci (2010), and achieved Membership to the Royal College of Physicians London and a Postgraduate Certificate in Medical Education with Distinction. Dr Noble’s has a particular in-

terest in mutliparametric MRI and has maintained links with the renal imaging group at The Sir Peter Mansfield Imaging Centre (SPMIC). As well as work in AKI, Dr Noble has also collaborated with SPMIC with work developing sodium MRI and evaluating the impact of dialysis on whole organ sodium levels. Currently Dr Noble is working towards a PhD with the University of Nottingham.

Daniela Viramontes-Horner, University of Nottingham UK

Daniela Viramontes-Horner graduated with honours from the BSc Nutrition and Dietetics, University of Guadalajara, Mexico in 2009, grad- uated with distinction from the MRes Dietet- ics, University of Nottingham in 2015, and was awarded PhD in the Centre for Kidney Re- search and Innovation, University of Nottingham in 2019. Dr. Viramontes-Ho ̈rner worked (2011- 2014) for a Mexican company (developing nutri- tional products for people with kidney disease) in the innovation, research and development

department leading randomised controlled clinical trials related with the effect of symbiotics on gastrointestinal symptoms, nutritional status, inflammation and kidney function in people with chronic kidney disease not on dialysis, as well as in people receiving haemodialysis. She is currently, a research fellow (level 4) working in the Centre for Kidney Research and Innovation, Academic Unit for Translational Medical Sci- ences, School of Medicine, University of Nottingham UK.

Maarten Taal, University of Nottingham UK

Maarten W. Taal received an MBChB in 1987 and MMed in 1997 from the University of Cape Town Medical School, South Africa. After com- pleting his post-graduate training in nephrology at Groote Schuur Hospital, Cape Town, he joined the Laboratory of Kidney and Electrolyte Physiol- ogy at Brigham and Women’s Hospital, Boston, USA under the directorship of Barry M. Bren- ner, MD. His research focused on mechanisms underlying the progression of chronic kidney disease and earned him a Doctor of Medicine

degree from the University of Cape Town in 2003.He subsequently moved to the United Kingdom where he was appointed a Consultant Renal Physician at Derby City General Hospital (now Royal Derby Hospital) in 2002 and Honorary Associate Professor at the University of Nottingham in 2011. He was appointed Professor of Medicine at the University on Nottingham in 2014, where he leads the Centre for Kidney Research and Innovation and was appointed Director of the Academic Unit for Translational Medical Sciences in 2021. He serves as an Editor for “Brenner and Rector’s The Kidney”, Section Editor for “Current Opinion in Nephrology and Hypertension” and Academic Editor for “PLOS Medicine”. He is a Past President of the British Renal Society and current Chair of the International Network of CKD Cohorts (research committee of the International Society of Nephrology).Prof Taal is a Fellow of the Royal College of Physicians and a Fellow of the Association of Physicians of Great Britain and Ireland.

Nicholas Selby, University of Nottingham UK

Micholas M. Selby studied medicine at the University of Nottingham, UK, graduating in 1998, and was appointed a full-time NHS consultant nephrologist at the Royal Derby Hospital in 2009. In 2015 he was appointed Associate Professor of Nephrology at the University of Nottingham, based in the Centre for Kidney Research and Innovation (; Twitter:@CKRIresearch), Royal Derby Hospital Postgraduate Medical School; in March 2020 he

was awarded a personal chair. Prof. Selby is a clinical academic with primary interests in Acute Kidney Injury (AKI), Magnetic Resonance Imaging (MRI) of the kidney and the haemodynamic consequences of dialysis. He led the development of one of the first e-alert systems for AKI in the UK and is CI on several investigator-instigated studies in these areas including AFiRM and MOSAICC. Prof Selby has been awarded peer-reviewed grant funding from NIHR, MRC, the Health Foundation, Kidney Research UK and British Renal Society, and has published over 100 peer-reviewed articles. Prof Selby has several national and international AKI roles, including immediate past chair of the AKI Clinical Study Group and UK Renal Imaging Network that sit within the UK Kidney Research Consortium and the ERA-EDTA Nephrology and Public Policy Committee for AKI. He is currently clinical lead for the Department of Renal Medicine at University Hospitals of Derby and Burton NHS Foundation Trust.