MD (Res)Traditional methods of measuring oxygen saturation, e.g. pulse oximetry, depend on
an adequate peripheral circulation and have a 20–30 second lag time before readings
are obtained. This was a series of evaluations of novel optical probes, designed to
measure oxygen saturation using fibreoptic technology directly from internal organs
including the brain, oesophagus and organs with splanchnic circulations. A series of
pilot studies were proposed and research ethics approval obtained to carry out
studies in humans, under general anaesthesia, using these probes. Innovative
reflectance probes were designed specifically for each of the four applications, so as
to obtain potentially useful signals needed for signal processing, analysis and
evaluation.
Signals were successfully obtained from the brain, oesophagus and splanchnic region
in almost all of the patients recruited. Good quality photoplethysmograph signals
were recorded and these were translated into clinically meaningful values of oxygen
saturation comparable to traditional methods of pulse oximetry. Overall, the signals
were prone to movement artefacts as well as occasional interference from surgical
diathermy and other sources. Nonetheless, the probes could prove to be a useful
alternative to conventional external transmittance pulse oximetry methods as well as
providing useful information regarding regional perfusion and oxygenation. The
success of these pilot studies will form the basis of more research in the area and
further development of such probes on the medical engineering front
