Introduction

The development of Doppler radar for remote sensing of vital signs, with proof of concept demonstrated for various applications, could offer a platform for unobtrusive, noncontact, yet continuous physiological monitoring systems. Early identification of patient deterioration is important, as it can prevent subsequent cardiopulmonary arrest and reduce mortality. Assessment of cardiopulmonary functions is most often performed with contact sensors when direct access to the subject is available. Monitoring the cardiac state of burn victims can be challenging because it is sometimes difficult to find enough skin on which to apply an electrocardiogram (ECG) electrode. Cardiopulmonary activity is the main parameter used in the study of sleep disorders. Widespread use of microwave technology and digital processors in common household communications devices has driven down costs, making it possible to develop practical radar monitors that cost significantly less than conventional cardiopulmonary assessment instruments.