A non-invasive method for estimating lung function

Conventional methods for monitoring lung function usually require complex gas analysers and the co-operation of the patient. Therefore, they are not compatible with the crowded environment of the Intensive Care Unit (ICU) or operating theatre, where the patient co-operation is usually impossible. However, it is precisely these patients that would benefit the most from 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.