Thoracic Electrical Bioimpedance Monitoring Research Articles

A novel non invasive measurement of hemodynamic parameters: Comparison of single-chamber ventricular and dual-chamber pacemaker

We carried out a cross sectional study to analyze hemodynamic parameters of single-chamber ventricular pacemaker compared with dual-chamber pacemaker by using thoracic electrical bioimpedance monitoring method (Physio Flow™) - a novel simple non-invasive measurement. A total of 48 consecutive outpatients comprised of 27 single chamber pacemaker and 21 dual chamber were analyzed. We measured cardiac parameters: heart rate, stroke volume index, cardiac output index, estimated ejection fraction, end diastolic volume, early diastolic function ratio, thoracic fluid index, and systemic parameters: left cardiac work index and systemic vascular resistance index. Baseline characteristic and pacemaker indication were similar in both groups. Cardiac parameters assessment revealed no significant difference between single-chamber pacemaker and dual-chamber pacemaker in heart rate, stroke volume index, cardiac index, estimated ejection fraction, end-diastolic volume, thoracic fluid index. There was significantly higher early diastolic function ratio in single-chamber pacemaker compared to dual-chamber pacemaker: 92% (10.2-187.7%) vs. 100.6% (48.7-403.2%); p=0.006. Systemic parameters assessment revealed significantly higher left cardiac work index in single-chamber group than dual-chamber group 4.9 kg.m/m² (2.8-7.6 kg.m/m²) vs. 4.3 kg.m/m² (2.9-7.2 kg.m/m²); p=0.004. There was no significant difference on systemic vascular resistance in single-chamber compared to dual-chamber pacemaker. Single-chamber ventricular pacemaker provides similar stroke volume, cardiac output and left cardiac work, compared to dual-chamber pacemaker. A non-invasive hemodynamic measurement using thoracic electrical bioimpedance is feasible for permanent pacemaker outpatients. (Med J Indones 2008; 17: 25-32)

Reliability and precision of a new thoracic electrical bioimpedance monitor in a lower body negative pressure model.

To evaluate the reliability and precision of measurement in a new thoracic electrical bioimpedance (TEB) monitor. Prospective clinical trial using healthy volunteers. Military tertiary care teaching hospital. Seventy-five healthy adult volunteers taking no medications. Induction of severe preload reduction using a standardized lower-body negative pressure protocol. Measurement of hemodynamic variables using a TEB monitor before, during, and immediately after application of negative pressure. Seventy-five subjects were enrolled and completed the study. Pulse, blood pressure, stroke index, cardiac index, systolic time ratios (STR), and index of contractility were obtained on all subjects undergoing monitoring with the lower body negative pressure (LBNP) device. Hemodynamic measurements were recorded at 15-sec intervals during incremental application of 0, -10, -20, -40, and -60 mm Hg pressure for 10 mins at each pressure. Maximal tolerated LBNP produced reductions in cardiac, stroke, and contractility indices of 50%, 65%, and 45%, respectively. Pulse and STRs increased 44% and 113%, respectively. The precision of measurement (mean +/- 2 SD) for TEB-derived cardiac and stroke index was 16% and 10%, respectively. Repeatability of measurement was assessed by measuring hemodynamic changes after the abrupt cessation of maximal LBNP. There were significant increases in stroke index (p < .001) and decreases in STRs (p < .001) and pulse (p < .001) 3 mins after LBNP. There was no significant difference between initial and post-LBNP cardiac index (p > .05). Regression equations were applied to scattergram plots of stroke index vs. STRs and index of contractility vs. body mass. The use of these plots allowed elimination of values that appeared to be spurious (stroke index vs. STRs) and also raised the question whether the Sramek-Bemstein equation (stroke volume = left ventricular ejection time x volume of electrically participating tissue x dZ/dt/Zo) fully explained all the factors affecting the TEB waveform. This new monitor appears to overcome many of the signal processing problems encountered with previous devices. The results clearly demonstrate that accurate and reliable measurement of bioimpedance waveforms is possible and suggest that the monitor is capable of generating precise hemodynamic data across a wide spectrum of hemodynamic alterations. However, the evidence also indicates that new algorithms may be needed to more fully explain the multiple factors affecting this waveform.

Managing inotrope therapy noninvasively.

Intermittent and continuous outpatient and home inotrope infusions have contributed to a decreased mortality rate and improved quality of life in the patient with end-stage congestive heat failure. Before the advent of noninvasive hemodynamic monitoring, available with thoracic electrical bioimpedance, initial dosage and titration were determined solely with invasively acquired data requiring hospital admission or with patients' subjective data. Thoracic electrical bioimpedance monitoring of patients receiving inotrope therapy provides objective documentation of drug efficacy, developing tolerance, and optimal dosage.

Thoracic-Fluid Conductivity in Peripartum Women With Pulmonary Edema

In Brief Objective To measure the level of thoracic-fluid conductivity associated with pulmonary edema in peripartum women by noninvasive thoracic electrical bioimpedance. Methods Between March 1994 and August 1996, 134 women were selected for thoracic electrical bioimpedance monitoring. Among them, 12 had pulmonary edema, 33 had severe preeclampsia, 17 had mild preeclampsia, and 72 were in uncomplicated early labor. Each subject's highest thoracic-fluid conductivity measurement was related to her clinical presentation. The Kruskal-Wallis one-way analysis of variance was used to compare groups' means. A receiver operating characteristic curve was used to identify thoracic-fluid conductivity values associated with pulmonary edema. Results Pulmonary edema was associated with severe preeclampsia in ten cases, urosepsis in one case, and postoperative volume overload in one case. Other than gestational age, there were no significant differences in maternal demographics between groups. Thoracic-fluid conductivity values in women with pulmonary edema (80.6 ± 18.3 kohm−1) were significantly higher than those in women with severe preeclampsia (62.8 ± 16.3 kohm−1), mild preeclampsia (53.3 ± 11.2 kohm−1), or early labor (41.3 ± 6.7 kohm−1). Thoracic-fluid conductivity of at least 65 kohm−1 best identified pulmonary edema (sensitivity 83.3%; specificity 86.9%; positive predictive value 38.5%; negative predictive value 98.1%). Conclusion Preeclampsia was associated with increased thoracic-fluid conductivity stratified between mild and severe disease. Thoracic-fluid conductivity of at least 65 kohm−1 was strongly associated with peripartum pulmonary edema. Women with values above 65 kohm−1 might be candidates for medical intervention even without overt clinical symptoms. Thoracic-fluid conductivity of at least 65 kohm−1 measured by noninvasive thoracic electrical bioimpedance is associated with peripartum pulmonary edema.

Thoracic-fluid conductivity in peripartum women with pulmonary edema

Objective: To measure the level of thoracic-fluid conductivity associated with pulmonary edema in peripartum women by noninvasive thoracic electrical bioimpedance. Methods: Between March 1994 and August 1996, 134 women were selected for thoracic electrical bioimpedance monitoring. Among them, 12 had pulmonary edema, 33 had severe preeclampsia, 17 had mild preeclampsia, and 72 were in uncomplicated early labor. Each subject’s highest thoracic-fluid conductivity measurement was related to her clinical presentation. The Kruskal-Wallis one-way analysis of variance was used to compare groups’ means. A receiver operating characteristic curve was used to identify thoracic-fluid conductivity values associated with pulmonary edema. Results: Pulmonary edema was associated with severe preeclampsia in ten cases, urosepsis in one case, and postoperative volume overload in one case. Other than gestational age, there were no significant differences in maternal demographics between groups. Thoracic-fluid conductivity values in women with pulmonary edema (80.6 ± 18.3 kohm −1) were significantly higher than those in women with severe preeclampsia (62.8 ± 16.3 kohm −1), mild preeclampsia (53.3 ± 11.2 kohm −1), or early labor (41.3 ± 6.7 kohm −1). Thoracic-fluid conductivity of at least 65 kohm −1 best identified pulmonary edema (sensitivity 83.3%; specificity 86.9%; positive predictive value 38.5%; negative predictive value 98.1%). Conclusion: Preeclampsia was associated with increased thoracic-fluid conductivity stratified between mild and severe disease. Thoracic-fluid conductivity of at least 65 kohm −1 was strongly associated with peripartum pulmonary edema. Women with values above 65 kohm −1 might be candidates for medical intervention even without overt clinical symptoms.

A longitudinal study of maternal hemodynamics during normal pregnancy

To investigate the maternal hemodynamic changes that occur during normal pregnancy. Serial hemodynamic investigations were performed throughout normal pregnancy by thoracic electrical bioimpedance monitoring in 50 healthy women. Analysis of variance with repeated measurements was used to evaluate the time course of a number of hemodynamic indies. The mean heart rate (+/- standard error [SE]) increased gradually from 87 +/- 2 beats per minute at 10-18 weeks' gestation to 92 +/- 1 beats per minute at 34-42 weeks' gestation. Mean arterial pressure decreased significantly after 14 weeks' gestation and increased significantly after 29 weeks' gestation. During the third trimester, mean cardiac output and mean stroke volume decreased, and mean systemic vascular resistance increased significantly. The course of cardiac output during the third trimester was not uniform in all women; it increased in nine and decreased in 41 women. A significantly higher mean cardiac output was found in nulliparous women compared with multiparous women (mean difference +/- SE 0.76 +/- 0.33 L/minute). The mean (+/- SE) cardiac output increased significantly from 6 (5.49 +/- 0.16 L/minute) to 12 weeks' postpartum (5.91 +/- 0.19 L/minute). Mean cardiac output and mean stroke volume decreased in late pregnancy. A significant difference in mean cardiac output was observed between nulliparous and multiparous women. Cardiac output usually, but not invariably, declined during the third trimester.

Use of cardiac index in pregnancy: Is it justified?

OBJECTIVE: The aim of this study was to test the hypothesis that standardization of cardiac output in pregnancy by correcting for body surface area, and thus obtaining cardiac index, is justified. STUDY DESIGN: Cardiac output was determined by thoracic electrical bioimpedance monitoring in 78 pregnant women; recordings were made at 1-month intervals from the first antenatal visit and a further two were made during the sixth and twelfth weeks after delivery. In a separate group of 10 pregnant women, cardiac output was determined by Doppler echocardiography at 5, 10, 14, 25, and 35 weeks and at 12 weeks post partum. RESULTS: Irrespective of gestational age, the correlation between cardiac output and body surface area was poor, by either thoracic electrical bioimpedance monitoring ( r = 0.015 to 0.39) or Doppler echocardiography ( r = 0.00 to 0.29). Furthermore, strict proportionality between cardiac output and body surface area was in general not the best way of describing the (poor) relation between these two. CONCLUSION: Standardization of cardiac output in pregnancy by correcting for body surface area to compare cardiac performance between individuals and between groups of individuals is not justified.

Systolic and diastolic time intervals in the critically ill patient

The waveform of the first derivative of thoracic electrical bioimpedance was used to calculate systolic time intervals of the cardiac cycle, preejection period/left ventricular ejection time ratio, and diastolic time intervals, isovolumic relaxation period/filling time ratio. Prospective clinical study. Waveforms were examined from 913 normal and abnormal tracings from a thoracic electrical bioimpedance monitor. This monitor was coupled to a two-channel strip-chart recorder that identified preejection period/LV ejection time and isovolumic relaxation period/filling time in 86% of the tracings. Two university-affiliated hospitals and one community hospital. We assessed 100 subjects (ranging in age from 17 to 93 yrs) under various conditions. Data from 15 normal subjects were used as a reference series to define normative values. Preejection period/left ventricular ejection time ratio was 0.35 +/- 0.1 (SD) and was consistent with data from systolic time intervals derived from simultaneous study of the ECG recording, carotid artery tracing, and phonocardiography. The diastolic time ratio (isovolumic relaxation period/filling time) was 0.4 +/- 0.2, in agreement with normal values derived by echocardiography and angiography. In a subgroup of 17 critically ill patients, a correlative study of simultaneously measured thoracic electrical bioimpedance, nuclear stethoscope, and radionuclide ventriculography was conducted. Systolic functions were compared by the ejection fraction derived by preejection period/left ventricular ejection time ratio displayed on the thoracic electrical bioimpedance monitor and by the radionuclide technique, and were found to be 57 +/- 13.8% and 58 +/- 8.6%, respectively (r2 = .49; y = 4.06x + 0.94; p less than .02; n = 17). Increased diastolic time ratios with normal or near-normal systolic time intervals were documented in nine (53%) of 17 critically ill patients with low systolic index. Both systolic and diastolic time intervals can be investigated noninvasively at the bedside by the thoracic electrical bioimpedance technique to provide a better understanding of left heart function.

Systolic time intervals during lower body negative pressure.

ArticleSystolic time intervals during lower body negative pressure.T B Graboys, F J Forlini Jr, and E D MichaelsonT B Graboys, F J Forlini Jr, and E D MichaelsonPublished Online:01 Sep 1974https://doi.org/10.1152/jappl.1974.37.3.329MoreSectionsPDF (956 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByEnabling the assessment of trauma-induced hemorrhage via smart wearable systemsScience Advances, Vol. 6, No. 30Functional effects of cardiac sympathetic denervation in neurogenic orthostatic hypotensionParkinsonism & Related Disorders, Vol. 15, No. 2Reliability and precision of a new thoracic electrical bioimpedance monitor in a lower body negative pressure modelCritical Care Medicine, Vol. 27, No. 9l-Tyrosine ameliorates some effects of lower body negative pressure stressPhysiology & Behavior, Vol. 57, No. 2Human cardiovascular reactions to simulated hypovolaemia, modified by the opiate antagonist naloxoneEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 57, No. 4Effect of Intermittent Positive Pressure Ventilation on Cardiac Systolic Time IntervalsActa Anaesthesiologica Scandinavica, Vol. 20, No. 4 More from this issue > Volume 37Issue 3September 1974Pages 329-32 https://doi.org/10.1152/jappl.1974.37.3.329PubMed4416040History Published online 1 September 1974 Published in print 1 September 1974 Metrics