Treffer: A microcomputer based non-invasive cardiopulmonary monitor using a microwave interferometer

With a microwave interferometer the vibrational velocity of the anterior (front), as well as posterior (back) chest wall can be monitored and recorded. The recorded signals are a reflection of the mechanical cardiac activity within the chest cavity, as opposed to Electrocardiogram (ECG) which is a reflection of the electrical cardiac activity. The interferometer recordings are obtained with no physical contact between the instrument and the subject. Moreover, the subject can be fully clothed since microwave energy readily passes through normal dry clothing. A microwave interferometer that is capable of detecting the vibrational velocity of the surfaces of the chest cavity (anterior and posterior) has been described in detail in the thesis. The objective of this research work is to monitor, record and analyze these vibrational characteristics of the chest wall using the microwave interferometer from co-operative healthy, normal subjects, both males as well as females, and thus to evaluate the possibility of using this instrument as a non-invasive and non-contacting cardiopulmonary monitor. The recordings from an ECG are very well understood by doctors and engineers today. By studying the signals obtained from the microwave interferometer with the ECG as a timing reference, and bearing in mind that certain mechanical cardiac events, such as valves opening and closing occur at certain points in the RR interval of the ECG, an attempt has been made to identify a common 'signature' or repetitive vibration pattern of the chest wall in normal, healthy male and female subjects. The interferometer data from one subject is autocorrelated to accentuate those features that are repetitive and also to attenuate the non-repetitive features. High amplitude velocity peaks are noticed at similar times within each cardiac cycle . In order to relate the timing of the peaks in the raw interferometer signal to the timing of certain known events in the cardiac cycle, such as the R wave of the ECG (recorded simultaneously), the ...