Cuffless Blood Pressure Measurement
: Comparison and Validation Study of the Arterial Waveforms

  • Ghalib Muhammad Waqas Janjua

Student thesis: Doctoral Thesis

Abstract

Hypertension is a silent killer, and one-third of its sufferers are unaware of its presence. Earlier hypertension detection can control cardiovascular morbidity and mortality, and interventions associated with changes in daily lifestyle can cure this disease. The noninvasive assessment of arterial stiffness has great significance for the monitoring of hypertension and related cardiovascular diseases (CVDs). However, the accuracy of current non-invasive assessments is usually poor due to the imprecise sensing of arterial waveforms. This study investigated non-invasive arterial stiffness assessment methods, using a piezoelectric sensor [ballistic pulse pressure (BPP)], compared with the use of the current state-of-the-art sensor, the photoplethysmogram (PPG) sensor, and further validated the BPP sensor against existing gold-standard devices and techniques.
In this study, the viability of a low-cost alternative to tonometric devices was demonstrated, using a BPP sensor that was validated against the current goldstandard tonometric device, with an r 2 value of 0.86. The BPP sensor does not require an operator and is a wearable, low-cost sensor that can accurately assess arterial stiffness, and these advantages are discussed, in detail. Furthermore, this study demonstrated the trackability and responsiveness of BPP arterial waveforms compared with electrocardiogram (ECG) waveforms, using the heart rate variability (HRV) technique. The surrogacy of the BPP waveforms for ECG waveforms was also established when using the HRV technique, with an r 2 value of 0.97. Another significant contribution of this study was the improvement of the pulse transit time (PTT) technique, which is conventionally used during cuffless blood pressure (BP) measurements. PTT measurements based on in-line BPP sensors were found to be more consistent for tracking fiducial parameters than current state-of-the-art in-line PPG sensors.
​​​​​​​Finally, the combination of both the BPP and PPG arterial waveforms resulted in the development of a novel, single-location estimation of arterial stiffness. The co-location of PPG and BPP sensors generated a pressure-volume loop, and the outcomes were reinforced by the phase-lag estimation between waveforms. This study was validated against the SphygmoCor carotid augmentation index, with an r 2 value of 0.71, which may advance modern technology for the early detection of CVD.
Date of AwardJan 2021
Original languageEnglish
SponsorsThis project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 676201.
SupervisorProfessor Jim McLaughlin (Supervisor) & Dewar Finlay (Supervisor)

Keywords

  • Augmentation index (AIx)
  • Finger ballistocardiogram (BPP)
  • Cuff-less blood pressure
  • Electrocardiogram (ECG)
  • Photoplethysmogram (PPG)
  • Pulse wave velocity (PWV)
  • Stiffness index (SI)
  • Reflection index (RI).

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