Non-invasive determination of blood pressure waveform from blood flow measurement

Arterial blood pressure can provide vital diagnostic and prognostic information on the state of the cardiovascular system. To date, most clinical non-invasive means of acquiring arterial blood pressure involve occlusive cuff procedures. While these methods provide a safe and reliable reading of systolic, mean, and diastolic pressure values, occlusive cuff methods cannot provide continuous blood pressure monitoring. When long term, continuous monitoring of arterial blood pressure is necessary, an invasive method of blood pressure measurement is often employed (i.e. catheterization). By using an invasive pressure transducer, monitoring can be continuous and the whole pressure waveform may be obtained. Analysis of the continuous pressure waveform can yield valuable information on the state of the cardiovascular system. However, catheterization is a procedure which presents some risks to the patient. The method for the acquisition of arterial blood pressure proposed in this paper is both noninvasive and non-occlusive. Based on the Navier-Stokes and the continuity equations of fluid flow, a transmission line model of a blood vessel is developed. The wave propagation coefficient is found using flow measurements at three sites along the vessel (such flow information can be obtained by non-invasive ultrasound methods.) From these data, the blood pressure waveform can be calculated. This method offers long term, continuous monitoring of the pressure waveform, while providing both the safety of indirect methods and the physiologic information of direct methods. This thesis reports a feasibility study of the procedure.