This thesis describes the development and assessment of an optical probe and instrument based on photoplethysmography (PPG) for monitoring of systolic blood pressure on the upper arm. The development procedure steps have included investigation of best probe position above the brachial artery, probe location underneath the occlusion cuff and also assessment of the ability of infrared light to mirror a blood flow related signal from a deeper vascular depth where the brachial artery is found. In addition, a digital PPG instrument has been developed and adapted to requirements from both a technical and clinical perspective. Design of algorithms for automatic blood pressure determination has been performed and used but they are not fully optimised yet. The technique was assessed in a study and the correlation factor, r=o.95. The difference between blood pressure obtained using the PPG method and invasive blood pressure was 3.9 ± 9.1 mmHg (mean± SD), n=19.

The work in this thesis demonstrates that PPG in combination with a specially designed probe can monitor the systolic blootl pressure at the upper arm. A robust algorithm for automatic pressure determination and presentation and a probe permanently integrated within the cuff is a prerequisite for the coming technical development. Recent technological developments facilitate ambulatory monitoring systems within which fields our system is clearly adaptable.