For decades, the monitoring of mixed venous oxygen saturation has been done
invasively using fibre-optic catheters. This procedure is not without risk as
complications may arise from catheterization. This thesis describes an alternative and
novel means of monitoring venous oxygen saturation. The technique outlined involves
inducing regular modulations of the venous blood volume and the associated
measurement of those modulations using an optical sensor. Just as pulse oximetry
utilizes the natural arterial pulse to perform spectral analysis of the peripheral blood in
order to estimate the arterial blood oxygen saturation, the new venous oximetry
technique uses the artificially generated pulse to perform the task of measuring
peripheral venous oxygen saturation.
This thesis explores and investigates the feasibility of this new venous oximetry
technique. A heuristic model was first developed to predict the effects of introducing
an artificially generated pulsatile signal in the venous system. The effect on the
underlying natural arterial pulsation was also examined. Experiments were then
conducted to justify and interpret the model developed. Other experiments were also
conducted to optimize the design of the artificial pulse-based venous oximeter, to
explore the effects of prolonged modulation of the venous system and to establish
evidence that the measurements made were indeed related to venous oxygen
It is concluded that the new venous oximetry technique is indeed feasible and with
further research and development would one day replace the current invasive method.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.