A Wearable Technology Revisited for Cardio-Respiratory Functional Exploration: Stroke Volume Estimation From Respiratory Inductive Plethysmography

International audienceThe objective of the present study is to extract new information from complex signals generated by Respiratory Inductive Plethysmography (RIP). This indirect cardio-respiratory (CR) measure is a well-known wearable solution. The authors applied time-scale analysis to estimate cardiac activity from thoracic volume variations, witnesses of CR interactions. Calibrated RIP signals gathered from 4 healthy volunteers in resting conditions are processed by Ensemble Empirical Mode Decomposition to extract cardiac volume signals and estimate stroke volumes. Averaged values of these stroke volumes (SVRIP) are compared with averaged values of stroke volumes determined simultaneously by electrical impedance cardiography (SVICG). There is a satisfactory correlation between SVRIP and SVICG (r=0.76, p<0.001) and the limits of agreement between the 2 types of measurements (±23%) satisfies the required criterion (±30%). The observed under-estimation (-58%) is argued. This validates the use of RIP for following stroke volume variations and suggests that one simple transducer can provide a quantitative exploration of both ventilatory and cardiac volumes

Comparison of Two Methods for Noninvasive Determination of Stroke Volume During Orthostatic Challenge

Background: The real time, beat-by-beat, non-invasive determination of stroke volume (SV) is an important parameter in many aerospace related physiologic protocols. In this study, we compared simultaneous estimates of SV calculated from peripheral pulse waveforms with a more conventional non-invasive technique. Methods: Using a prospective, randomized blinded protocol, ten males and nine females completed 12-mm tilt table protocols. The relative change (%(Delta)) in beat-to-beat SV was estimated non-invasively from changes in pulse waveforms measured by application of infrared finger photoplethysmography (IFP) with a Portapres(Registered TradeMark) blood pressure monitoring device and by thoracic impedance cardiography (TIC). The %(Delta) SV values were calculated from continuous SV measurements in the supine posture and over the first 10 s (T1), second 10 s (T2), and 3.5 minutes (T3) of 80deg head-up tilt (HUT). Results: The average %(Delta) SV measured by IFP at T1 (-11.7 +/- 3.7 %) was statistically less (P or = 0.322) than the average %(Delta) SV measured by TIC at T2 (-21.8 +/- 2.5 %), and T3 (-22.6 +/- 2.9 %). Correlation coefficients (r(sup 2)) between IFP and TIC were 0.117 (T1), 0.387 (T2), and 0.7 18 (T3). Conclusion: IFP provides beat-to-beat (real time) assessment of %(Delta) SV after 20 sec of transition to an orthostatic challenge that is comparable to the commonly accepted TIC. Our data support the notion that IFP technology which has flown during space missions can be used to accurately assess physiological status and countermeasure effectiveness for orth static problems that may arise in astronauts after space flight. While the peripherally measured IFP response is slightly delayed, the ease of implementing this monitor in the field is advantageous

Physiologic and Clinical Principles behind Noninvasive Resuscitation Techniques and Cardiac Output Monitoring

Clinical assessment and vital signs are poor predictors of the overall hemodynamic state. Optimal measurement of the response to fluid resuscitation and hemodynamics has previously required invasive measurement with radial and pulmonary artery catheterization. Newer noninvasive resuscitation technology offers the hope of more accurately and safely monitoring a broader range of critically ill patients while using fewer resources. Fluid responsiveness, the cardiac response to volume loading, represents a dynamic method of improving upon the assessment of preload when compared to static measures like central venous pressure. Multiple new hemodynamic monitors now exist that can noninvasively report cardiac output and oxygen delivery in a continuous manner. Proper assessment of the potential future role of these techniques in resuscitation requires understanding the underlying physiologic and clinical principles, reviewing the most recent literature examining their clinical validity, and evaluating their respective advantages and limitations

Development and Evaluation of an Impedance Cardiographic System to Measure Cardiac Output and Other Cardiac Parameters, 1 July 1968 - 30 June 1969

Impedance cardiographic system to measure cardiac output and cardiovascular function

Thoracic electrical bioimpedance theory and clinical possibilities in perioperative medicine

This article is a short review of thoracic electrical bioimpedance (TEB) theory and clinical capabilities. Cardiac output measurement is used primarily to guide therapy in complex, critically ill patients. Thoracic electrical bioimpedance is one of several noninvasive techniques that have been investigated to measure cardiac output and other hemodynamic parameters. Opinions in current literature continue to be conflicting as to the utility of thoracic electrical bioimpedance to that purpose. There is a limited number of good designed studies but they imply TEB is an accurate and reliable noninvasive method for determining cardiac output/cardiac index and it would be valuable for patients and circumstances in which intracardiac pressures and mixed venous blood samples are not necessary

Impedancia kardiográfia alkalmazása a gyermekaneszteziológiai és intenzív terápiás gyakorlatban

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Assessment of stroke volumeindex with three different bioimpedance algorithms: lack of agreement compared to thermodilution

Objective: The accuracy of bioimpedance stroke volume index (SVI) is questionable as studies report inconsistent results. It remains unclear whether the algorithms alone are responsible for these findings. We analyzed the raw impedance data with three algorithms and compared bioimpedance SVI to transpulmonary thermodilution (SVITD). Design and setting: Prospective observational clinical study in a university hospital. Patients: Twenty adult patients scheduled for coronary artery bypass grafting (CABG). Interventions: SVITD and bioimpedance parameters were simultaneously obtained before surgery (t1), after bypass (t2), after sternal closure (t3), at the intensive care unit (t4), at normothermia (t5), after extubation (t6) and before discharge (t7). Bioimpedance data were analyzed off-line using cylinder (Kubicek: SVIK; Wang: SVIW) and truncated cone based algorithms (Sramek-Bernstein: SVISB). Measurements and results: Bias and precision between the SVITD and SVIK, SVISB, and SVIW was 1.0± 10.8, 9.8± 11.4, and -15.7± 8.2ml/m2 respectively, while the mean error was abundantly above 30%. Analysis of data per time moment resulted in a mean error above 30%, except for SVIW at t2 (28%). Conclusions: Estimation of SVI by cylinder or truncated cone based algorithms is not reliable for clinical decision making in patients undergoing CABG surgery. A more robust approach for estimating bioimpedance based SVI may exclude inconsistencies in the underlying algorithms in existing thoracic bioimpedance cardiography devices

The impedance cardiography technique in medical diagnosis

Background: Thoracic Electrical Bioimpedance (TEB) Technology sometimes called the Impedance Cardiography (ICG). &nbsp;In 1940, the Impedance Cardiography emerged; the studies of this technique are realized to the cardiovascular diseases detection which used hemodynamic parameters measurements based on the skin electrodes contact by injecting a low amplitude alternating signal. The objective of this article is to review the various studies based on this signal type and to present the multiple methods used for the treatment and to have a correct analysis. Methods: This ICG technique consists for applying an electric field longitudinally across a segment of the thorax with amplitude in mean, high frequency and low amplitude current. To analyze the ICG signal, the signal denoising is necessary that’s why a multiple filters are proposed, and the Discrete Wavelet Transform (DWT) denoising is also used. Results: The ICG is considered advantageous compared to other invasive conventional techniques; it gives a good correlation, and solves the Doppler ultrasound and Thermodilution problems. According to the studies, the Daubechies wavelet family (db8) is the best DWT to eliminate the noises. There are several algorithms for the signal characteristic point’s detection. Conclusion: For the purpose of cardiovascular disease diagnosis and monitoring, the non-invasive ICG technique comes to solve the complexity problem for measurement and analyzing heart disease based on the thoracic electrical impedance change assessment that is due to blood velocity and resistivity changes (blood volume changes) in order to estimate several hemodynamic parameters. Keywords: ICG, cardiovascular disease, hemodynamic parameters, diagnosis and monitoring, correct analysis. &nbsp

Development and clinical application of impedance pneumography technique

Assessment of the lung function is essential in the diagnosis and management of respiratory disease such as asthma. However, conventional spirometry requires difficult manoeuvres from the subject and is thus unsuitable for young children and infants. This renders the diagnosis of childhood asthma often qualitative, time-consuming and clinically challenging. However, information relating to the lung function can be derived from restful tidal breathing (TB) as well. Traditionally TB has been recorded in short intervals in laboratory conditions with obtrusive instrumentation using a face mask or a mouth piece. The principal aim of this thesis was to develop a noninvasive and convenient, yet highly accurate method for recording TB over extended time periods for clinical purposes, especially in young children. The measurement methodology developed within this thesis is based on impedance pneumography (IP), where breathing is recorded through the respiratory variations of the electrical impedance of the thorax. This is established by placing four skin electrodes on the upper body and connecting them to a recording device. The main focus was in ensuring the accuracy of the IP-derived tidal flow recording as compared to direct measurement from the mouth. This was established by attenuating the distortive cardiac oscillations (CGO) of the impedance signal and by optimising the locations of the skin electrodes. The complete method was then validated in healthy adults during respiratory loading (n=17) and in preschool children with wheezing disorder (n=20). The CGO attenuation was realised through an ensemble averaging based signal processing algorithm. The algorithm takes into account the respiratory modulation of the CGO waveform thus enabling efficient CGO attenuation while preserving the respiratory component of the signal unchanged. The newly proposed electrode configuration provides consistently more linear impedance to lung volume ratio than those previously established in the literature. The complete method integrating these developments provided highly accurate TB flow signal during normal and altered respiratory mechanics (loading) in adults and during induced bronchoconstriction in young children. It may be concluded that in this thesis significant improvements were realised with the IP technique. These improvements were experimentally validated in two studies and the integrated system was found to consistently provide an accurate respiratory flow signal. The method may have clinical implications for the diagnosis of respiratory diseases especially in non-cooperative subjects, such as young children

Sports medicine and rehabilitation : clinical and experimental studies : review articles

• Arak, A. Quality of Life After Coronary Bypass Surgery • Audova, M. Electrotherapy: A Part of Rehabilitation of Hand and Leg Fractured Patients • Eller, A., Tein, T., Pintsaar, A. First experience of arthroscopy: success, difficulties, complications • Jaksman, S., Vedru, J., Vider, J. On the Proper Cuff Pressure for Venous Occlusion • Kaljumäe, Ü., Airaksinen, O., Turunen, H., Hänninen, O. Knee Antagonist Muscle Coactivity During Fatiguing Exercise • Karu, T., Kaljumäe, Ü., Slavin, G., Hänninen, О. Computing Aerobic and Anaerobic Load Periods From Heart Rate Records in Runner • Kullus, R., Laane, E., Saks, K., Pokk, T. Oxygen Uptake and Noninvasive Hemodynamic Assessment in Patients With Coronary Heart Disease • Landõr, A., Karu, T., Ojamaa, M. Standards for Evaluating Morphologic and Physical Capacity Indices in Men • Landõr, A., Täil, S., Ignatjeva, N., Savi, T. Fittness, Physical Activity and Serum Cholesterol of Men of Different Age Groups • Maaroos, J. Children in Competitive Sports • Ojamaa, M., Viigimaa, M., Ulst, K., Altraja, E. Myocardial Perfusion Imaging and Coronary Angiography in the Diagnosis of Coronary Artery Disease • Vedru, J. Electrical Impedance Methods for the Measurement of Stroke Volume in Man: State of Arthttp://tartu.ester.ee/record=b1077866~S1*es