Noninvasive microwave technique for hemodynamic assessments

Pulmonary edema, accumulation of fluid in the lungs is often measured and analyzed after medical and surgical procedures, since pulmonary edema is commonly linked to cases of congestive heart failure (CHF) and kidney failures. Like pulmonary edema, hemodynamic assessments do not occur until after an acute cardiac episode. Early detection of pulmonary edema and routine monitoring of cardiac functions such as cardiac output (CO) the product of stroke volume and heart rate, would be beneficial for surgical patients as well as others suffering from acute cardiac and pulmonary illnesses. Available diagnostic tools such as the Pulmonary Artery Catheterization are invasive and diagnostic techniques such as Magnetic Resonance Imaging (MRI) or Computerized Active Tomography (CAT) Scans are expensive, cumbersome, and not suitable for continuous monitoring. In addition, techniques such as the double indicator dilution method, the electrical impedance plethysmography, and the re-breathing method are impractical for clinical use because of limitations on sensitivity, consistency, and simplicity [1]. To overcome difficulties with above conventional techniques, an electromagnetic (EM) method has been investigated for this application. Specifically, an EM energy coupler and the associated measurement method have been developed to simultaneously measure breathing rate in addition to the changes in lung water content [2,3]. Specifically, a two-port EM sensor has been developed for animal and phantom experiments [3-5]. In these phantom and animal experiments it is shown that variation of lung water contents and breathing rate can clearly be monitored by the proposed technique.