Phonocardiography. I. General principles and problems of standardization

Human Vital Signs Detection Methods and Potential Using Radars: A Review

Continuous monitoring of vital signs, such as respiration and heartbeat, plays a crucial role in early detection and even prediction of conditions that may affect the wellbeing of the patient. Sensing vital signs can be categorized into: contact-based techniques and contactless based techniques. Conventional clinical methods of detecting these vital signs require the use of contact sensors, which may not be practical for long duration monitoring and less convenient for repeatable measurements. On the other hand, wireless vital signs detection using radars has the distinct advantage of not requiring the attachment of electrodes to the subject's body and hence not constraining the movement of the person and eliminating the possibility of skin irritation. In addition, it removes the need for wires and limitation of access to patients, especially for children and the elderly. This paper presents a thorough review on the traditional methods of monitoring cardio-pulmonary rates as well as the potential of replacing these systems with radar-based techniques. The paper also highlights the challenges that radar-based vital signs monitoring methods need to overcome to gain acceptance in the healthcare field. A proof-of-concept of a radar-based vital sign detection system is presented together with promising measurement results.

Hemodynamic Correlates of the Various Components of the First Heart Sound

Previous studies in this laboratory having demonstrated that AV valve closure is not directly responsible for the rapid vibrations of the first heart sound, the mechanism of production of this "sound" was studied further in 30 experiments in dogs. The experiments were performed with multiple pressure catheterization, and intracardiac phonocatheterization, and were compared with external phonocardiograms and electrocardiograms. In 10 experiments, the first derivatives of the left and right ventricular pressures were also recorded. In four experiments, direct epicardial and arterial sound tracings were obtained.

These experiments revealed that three groups of vibrations, or components, were often visible in the external phonocardiogram, and in intracardiac and epicardial tracings. The first component follows the onset of left ventricular pressure rise and closure of the mitral valve but coincides with the rapid rise of the first derivative of LV pressure. The second component has no relationship with right heart events, occurs before aortic valve opening, and coincides with the sudden change of course of the first derivative of LV pressure. The third component occurs slightly after aortic valve opening, and seems related to sudden increase of aortic wall tension. It is probably the physiological equivalent of the aortic "ejection sound." Thus, the first two components are both left ventricular in origin while the third is of aortic origin.