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Title: Non-invasive monitoring of peripheral perfusion : an exploration of non-invasive peripheral perfusion monitoring for applications in research & healthcare
Author: Blaxter, Laurence
ISNI:       0000 0004 5988 9529
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2015
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The need for real-time, prognostic perfusion data has been widely recognised in clinical practice and academia. Perfusion, the volumetric blood low to tissue, is an important tool for haemodynamic monitoring, since perfusion adequacy is vital to tissue health. Perfusion can serve as both a diagnostic indicator and a fundamental research tool. However, lack of a low cost, easily applied, and non-invasive sensor technology capable of measuring peripheral perfusion in absolute volumetric units is clearly a major factor preventing the widespread clinical use of perfusion monitoring. This thesis explores and evaluates potential techniques for the non-invasive measurement of peripheral perfusion in absolute volumetric units. Following a review of applicable technologies, a small selection of complementary optical methods are selected for study based on economic and technology readiness arguments, and a series of volunteer studies conducted to evaluate these using both of the shelf and prototype apparatus. A study of healthy adult and child volunteers demonstrates that Laser Doppler flowmetry (LD) outperforms both pulse oximeter derived Perfusion Index (PI), and a novel Capillary Refill Time (CRT) measurement device by a considerable margin in a cold challenge test. The PI metric had the lowest correlation with temperature, suggesting it is the least effective perfusion analogue of the three. A novel filtering algorithm is presented for removal of artefacts from raw LD flowmetry data. CRT was found to significantly correlate with short period oscillations in LD perfusion. A second study combined CRT with NIRS, allowing tissue haemoglobin concentrations to be estimated. Studies of the palm of healthy volunteers hands using this device, in combination with cooling and/or venous and arterial occlusion, demonstrate both that capillary refill measures blood mobility within the capillary bed, and that NIRS with venous occlusion is an effective method for measurement of absolute perfusion. Although LD was the most effective existing solution, and CRT has potential, only thermal techniques and NIRS with venous occlusion allow practical, low cost quantification of absolute perfusion. Development of a thermal diffusion sensor is recommended.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: RC Internal medicine