Development of novel methods for non-invasive measurement of cardiac output and lung volume during anaesthesia

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In Australia approximately 2 million anaesthetic procedures are performed annually. Approximately one patient in 20,000 dies during or shortly after an anaesthetic from complications related to the anaesthetic itself, and as many as one in 170 suffers severe complications. Mortality and severe morbidity are often ultimately associated with lack of oxygen in the tissues. Oxygen is transported from the lungs to the tissues by the blood. The oxygen content of arterial blood is monitored by pulse oximetry during every anaesthetic, but blood flow is not. Cardiac output is measured in only a very small proportion of anaesthetised patients using intravenous catheters that pass through the heart to the lungs. This procedure is invasive and is associated with significant morbidity and mortality. At present there is no easy way to monitor cardiac output non-invasively during anaesthesia. Our proposed research project, currently underway in conjunction with an industrial partner, is aimed at the development of a reliable, rapidly repeating, non-invasive method for monitoring total cardiac output and lung volume in every patient who has an anaesthetic. The purpose of the new monitor is to ensure that potential problems with oxygen supply to the tissues are detected and corrected promptly. Our new monitoring technique is computer-controlled, can function without intervention by the anaesthetist and has very few side-effects. It can be added to any anaesthetic machine. Such a measurement technique is likely to have an impact on anaesthesia similar to that of pulse oximetry in the 1980's, and, if suitably adapted, is likely to find applications in other fields, such as intensive care, sports medicine, the respiratory function laboratory and in veterinary medicine.