Signal Processing the Human Circulatory System for Stability and Regulation

Abstract

During this project the components of the circulatory profile of a patient before a cardiac surgery have been analyzed and compared to the perturbed circulatory profile components of the same patient after having a cardiac surgery. All this data is compared to the usual values of a healthy person as well. The data recorded previous to the surgery, is used as a baseline and compared to the data after the surgery. The data is studied and analyzed in order to create a connection between those two profiles. Making use of the comparison between the two types of data patterns, a characterizing profile and patterns are tried to find to understand the regulation of the circulatory system and try to relate them to control theory techniques. For that purpose frequency and time analysis is performed. At the beginning of the project, the information regarding the different medicines that were applying to the patients after having the surgery, in order to see how the body was reacting to the drugs was expected. But that information has not been available, so it has not be possible to predict when giving certain drugs to the human being, how the body was going to react. For example if a vasodilator was giving to a patient, its effects should be visible in the immediate time period, and based on that and using control theory techniques a model could be made. As the necessary information to perform that model was not given, other features have been analyzed in the available data and control theory has been studied. From the analysis of the results it has been observed that there are some common aspects in all the patients before and after the surgery, for example the low values of the R wave amplitude and the diastolic blood pressure. In the frequency domain how most of the energy is around 0-1Hz as expected, can be seen. In total, the data recorded from 6 patients has been analyzed. All the patients that have collaborated to collect data for this purpose suffer from heart diseases and are considered stable Coronary Artery Bypass Grafting (CABG) patients to standard elective and urgent operation, and are signing a written consent. CABG is a kind of surgery which aim is to improve the blood flow to the heart. All the recordings have been performed at St Olav Hospital Cardiothoracic Intensive Care Unit and a consulting cardiothoracic anesthesiologist is present at all moment. The study has been approved by the Norwegian Regional Ethics Committee and the data is registered in the ClinicalTrial.org database.