A non-invasive method for estimating lung function

Andrew D Farmery and Clive E W Hahn are with Nuffield Department of Anaesthetics, University of Oxford, Oxford, UK. Email: andrew. [email protected] / [email protected] Conventional methods for monitoring lung function usually require complex gas analysers and the cooperation of the patient. Therefore, they are not compatible with the crowded environment of the intensive care unit (ICU) or operating theatre, where patient cooperation is usually impossible. However, it is precisely these patients that would benefit the most from an accurate monitoring of lung function. This paper develops a compact and non-invasive system for the measurement and monitoring of lung function in a clinical setting, such as lung volume, airway dead space volume and pulmonary blood flow. In contrast with conventional methods, the compact apparatus and non-invasive nature of the proposed method allow it to be used in the ICU, as well as in general clinical settings. The system implements a breath-by-breath computer ventilation model using a non-invasive technique, in which a tracer gas is injected into the patient’s inspired breath. Experimental results are shown for both an artificial lung and a healthy volunteer. Our findings show that the proposed technique has several advantages over the conventional method for the estimation of lung function.