Respired gas measurements with diode lasers

The uptake of oxygen and excretion of carbon dioxide by the lungs gives a measure of the body s metabolism. Measurements of these gases are required for monitoring clinical procedures such as anaesthesia, and are also necessary in experimental medicine, where the aim is to understand their involvement in biological regulation. The problem in such measurements is that they need to be direct and fast, so that changes during the breath cycle can be accurately monitored. This proposal seeks to introduce novel methods of laser absorption into a clinical setting by adapting present techniques used in a physical chemistry laboratory so that they can be applied in medical monitoring and investigation.

New technologies will be developed for the measurement of the changes in oxygen, water vapour and carbon dioxide in respired gas. The methods, using sensitive and selective laser absorption techniques, will offer significant advantages over existing instrumentation, and will allow effectively instantaneous analysis directly within the respired gas stream. This will have applications in a number of clinical and research areas where existing technologies are unsatisfactory.