Abstract
Objective: Intradialytic haemodynamic instability is a significant clinical problem, leading to end-organ ischaemia and contributing to morbidity and mortality in haemodialysis patients. Non-invasive continuous blood pressure monitoring is not currently part of routine practice but may aid detection and prevention of significant falls in blood pressure during dialysis. Brachial blood pressure is currently recorded intermittently during haemodialysis via a sphygmomanometer. Current methods of continuous non-invasive blood pressure monitoring tend to restrict movement, can be sensitive to external disturbances and patient movement, and can be uncomfortable for the wearer. Additionally, poor patient blood circulation can lead to unreliable measurements. In this feasibility study we performed an initial validation of a novel method and associated technology to continuously estimate blood pressure using pressure sensors in the extra-corporeal dialysis circuit, which does not require any direct contact with the person receiving dialysis treatment. Method: The paper describes the development of the measurement system and subsequent in vivo patient feasibility study with concurrent measurement validation by Finapres Nova physiological measurement device. Real-time physiological data is collected over the entire period of (typically 4-hour) dialysis treatment. Results: We identify a quasi-linear mathematical function to describe the relationship between arterial line pressure and brachial artery BP, which is confirmed in a patient study. The results from this observational study suggest that it is feasible to derive a continuous measurement of brachial pressure from continuous measurements of arterial and venous line pressures via an empirically based and updated mathematical model. Conclusion: The methodology presented requires no interfacing to proprietary dialysis machine systems, no sensors to be attached to the patient directly, and is robust to patient movement during treatment and also to the effects of the cyclical pressure waveforms induced by the hemodialysis peristaltic blood pump. This represents a key enabling factor to the development of a practical continuous blood pressure monitoring device for dialysis patients.
Highlights
Patients receiving hemodialysis treatment as a result of end-stage kidney disease (ESKD) are at a much higher risk of mortality due to cardiovascular disease (CVD) [1]
A key factor contributing to CVD is intradialytic hypotension, a frequent complication affecting 15% − 50% of treatments which is associated with subsequent vascular access thrombosis, inadequate dialysis dose, cardiac dysfunction and mortality
Arterial line pressure sensor data was analysed for dialysis pump flow by fitting a Fourier model to the continuous venous line pressure signal
Summary
Patients receiving hemodialysis treatment as a result of end-stage kidney disease (ESKD) are at a much higher risk of mortality due to cardiovascular disease (CVD) [1]. A feasibility study based around a novel method for continuously monitoring BP is described which involves the placement of pressure transducers onto the venous and arterial blood lines that connect a patient to a haemodialysis machine during treatment. A. METHOD The aim of this feasibility study is to identify and experimentally derive relationships between the patient’s brachial BP, and the pressures recorded within the extra-corporeal blood lines to and from the dialysis machine. The pump frequency can be derived from a real-time positive pressure sensor sited in the venous air trap by the application of Fourier analysis By this method, any reasonably well-behaved function can be written in terms of trigonometric or exponential functions. All data streams are time synchronised via a common real-time clock
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