Evaluation Of Cardiac Output By Bioimpedance Method

This book deals with the possibility of using impedance cardiography for calculation of cardiac output. Kubicek's, Sramek's and Sramek-Bernstein's methods are discussed here. These methods were applied to a data set, obtained by measuring on subjects with implanted pacemakers. The subjects' heart rate was being changed by the programming of pacemakers. Thanks to this procedure the measured data were not affected by artifacts, connected with the heart rate change caused by a body stress, or other influences. An influence of heart rate on a cardiac output value based on the statistical processing of the data set was studied.

Electrical bioimpedance is a method used to determine stroke volume and cardiac output from thoracic tissue resistance to an imposed alternating electric current. The basic rationale for the use of electrical bioimpedance for the measurement of cardiac output is that the procedure is mechanically noninvasive. Information obtained from a review of the litera- ture, responses to a Federal Register notice of this assessment, PHS agencies, and medical specialty groups suggested that despite the obvious potential advantages of electrical bioimpedance, the technique has not been validated in a trail with a statistically satisfactory number of subjects. In addition, the potential electrical effects of long-term monitoring have not been studied, and the precision and accuracy of this technology in severely ill patients has not been compared to standard techniques of measuring cardiac support.

This book, part of the European Society of Intensive Care Medicine textbook series, teaches readers how to use hemodynamic monitoring, an essential skill for today’s intensivists. It offers a valuable guide for beginners, as well as for experienced intensivists who want to hone their skills, helping both groups detect an inadequacy of perfusion and make the right choices to achieve the main goal of hemodynamic monitoring in the critically ill, i.e., to correctly assess the cardiovascular system and its response to tissue oxygen demands. The book is divided into distinguished sections: from physiology to pathophysiology; clinical assessment and measurements; and clinical practice achievements including techniques, the basic goals in clinical practice as well as the more appropriate hemodynamic therapy to be applied in different conditions. All chapters use a learning-oriented style, with practical examples, key points and take home messages, helping readers quickly absorb the content and, at the same time, apply what they have learned in the clinical setting. The European Society of Intensive Care Medicine has developed the Lessons from the ICU series with the vision of providing focused and state-of-the-art overviews of central topics in Intensive Care and optimal resources for clinicians working in Intensive Care.

This is the newest volume in the softcover series "Update in Intensive Care Medicine". It takes a novel, practical approach to analyzing hemodynamic monitoring, focusing on the patient and outcomes based on disease, treatment options and relevance of monitoring to direct patient care. It will rapidly become a classic in the approach to patient monitoring and management during critical illness.

Abstract: OBJECTIVE: The purposes of this study were to determine if relationships existed between cracking pressures of -7, -11, -15, and -19 cm H2O vs. cardiopulmonary physiologic parameters and Borg scale scores for healthy adults and to determine the maximum cracking pressure which does not produce a Borg score greater than 6. DESIGN: The study was designed as single blinded, randomized, and quasi-experimental with repeated measurements. Subjects served as their own controls. SETTING: Laboratory. SUBJECTS: 21 healthy, normotensive, normovolemic volunteers. METHODS: Subjects were continuously observed and monitored using bioimpedance for non-invasive cardiac output and heart rate, respiratory frequency and pulse oximetry. Subjects breathed through an Impedance Threshold Device (ITD) alternating between two-minute intervals of zero resistance and resistances of -7, -11, -15, and -19 cm H2O pressure. For randomization, subjects selected pre-set ITDs from a set of 4. During each level of resistance, maximum changes from baseline of cardiac output (CO), heart rate (HR), blood pressure (BP), respiratory rate (RR) and arterial oxygen saturation (SpO2) were recorded and subjects indicated their subjective feeling of exertion based on a Borg scale score from 1 to 10. RESULTS: There was a statistically significant strong negative correlation between cracking pressures and Borg scale scores (r = -0.814, p