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Videodensitometric Methods for Cardiac Output Measurements  [cached]
Mischi Massimo,Kalker Ton,Korsten Erik
EURASIP Journal on Advances in Signal Processing , 2003,
Abstract: Cardiac output is often measured by indicator dilution techniques, usually based on dye or cold saline injections. Developments of more stable ultrasound contrast agents (UCA) are leading to new noninvasive indicator dilution methods. However, several problems concerning the interpretation of dilution curves as detected by ultrasound transducers have arisen. This paper presents a method for blood flow measurements based on UCA dilution. Dilution curves are determined by real-time densitometric analysis of the video output of an ultrasound scanner and are automatically fitted by the Local Density Random Walk model. A new fitting algorithm based on multiple linear regression is developed. Calibration, that is, the relation between videodensity and UCA concentration, is modelled by in vitro experimentation. The flow measurement system is validated by in vitro perfusion of SonoVue contrast agent. The results show an accurate dilution curve fit and flow estimation with determination coefficient larger than 0.95 and 0.99, respectively.
A Numerical Investigation of Heat Transfer Cardiac Output Measurements  [PDF]
P. Fotheringham,A. R. Gourlay,S. Mckee,S. Andrews
Computational and Mathematical Methods in Medicine , 2005, DOI: 10.1080/10273660500158712
Abstract: Measurement of cardiac output is often investigated using a technique based on hot-film anemometry. Here, we discuss a modification to hot-film anemometry, which involves a cylindrical heating element mounted flush on the surface of a typical Swan-Ganz catheter. In contrast to traditional thermodilution, the method discussed here has the potential to allow continuous monitoring of cardiac output.
Cardiac output measurements using the bioreactance technique in critically ill patients
David Fagnoul, Jean-Louis Vincent, De Daniel Backer
Critical Care , 2012, DOI: 10.1186/cc11481
Abstract: Measurement of cardiac output (CO) requires use of invasive or minimally invasive devices; the use of noninvasive and minimally invasive devices has gained popularity in recent years. The bioreactance technique is a relatively new, continuous, totally non-invasive technique for measuring CO that is easily implemented. This new technique involves analyzing phase shifts of a delivered oscillating current that occur when the current traverses the thoracic cavity [1], and differs from traditional bioimpedance techniques that rely on analysis of changes in signal amplitude. Most validation studies in critically ill patients have shown good correlation and/or agreement of bioreactance values compared with CO values obtained using other devices in patients admitted after cardiac surgery [2-4]. However, validation in critically ill patients is lacking.As part of the internal evaluation of a bioreactance device before its implementation in the unit (evaluation of new non-invasive monitoring systems before introduction in the unit does not require the approval of the ethics committee in our institution), we compared CO values obtained using the bioreactance technique (NICOM system; Cheetah Medical Inc., Portland, OR, USA) with those measured using semi-continuous cardiac output by thermodilution (CCO) with a pulmonary artery catheter (Vigilance, Edwards LifeSciences, Irvine, CA, USA). In 11 patients the CO values were compared at study inclusion and each time a relevant change in hemodynamics and/or in therapeutics (for example, fluid challenge, inotrope or vasopressor infusions) was observed (Table 1).We recorded bioreactance CO (average of five values over a 5-minute period) just after obtaining the pulmonary artery catheter CCO (average of five CCO values over a 5-minute period). We collected 141 pairs of measurements (3 to 23 per patient); the duration of monitoring was at least 3 hours but never exceeded 24 hours. The pulmonary artery catheter CCO values ranged from 3.9
Cardiac Output Measurements in Septic Patients: Comparing the Accuracy of USCOM to PiCCO  [PDF]
Sophia Horster,Hans-Joachim Stemmler,Nina Strecker,Florian Brettner,Andreas Hausmann,Jitske Cnossen,Klaus G. Parhofer,Thomas Nickel,Sandra Geiger
Critical Care Research and Practice , 2012, DOI: 10.1155/2012/270631
Abstract: USCOM is an ultrasound-based method which has been accepted for noninvasive hemodynamic monitoring in various clinical conditions (USCOM, Ultrasonic cardiac output monitoring). The present study aimed at comparing the accuracy of the USCOM device with that of the thermodilution technique in patients with septicemia. We conducted a prospective observational study in a medical but noncardiological ICU of a university hospital. Septic adult patients (median age 55 years, median SAPS-II-Score 43 points) on mechanical ventilation and catecholamine support were monitored with USCOM and PiCCO ( ). Seventy paired left-sided CO measurements (transaortic access?=?COUS-A) were obtained. The mean COUS-A were 6.55?l/min (±2.19) versus COPiCCO 6.5?l/min (±2.18). The correlation coefficient was . Comparison by Bland-Altman analysis revealed a bias of ?0.36?l/min (±0.99?l/min) leading to a mean percentage error of 29%. USCOM is a feasible and rapid method to evaluate CO in septic patients. USCOM does reliably represent CO values as compared to the reference technique based on thermodilution (PiCCO). It seems to be appropriate in situations where CO measurements are most pertinent to patient management. 1. Introduction Thermodilution cardiac output measurements have been routinely performed as part of intensive care practice since the introduction of the balloon-directed, thermistor-tipped pulmonary artery catheter in the 1970s [1–3]. Introduced by Swan and Ganz, the pulmonary artery catheter (PAC) became to be the gold standard for more than two decades [1, 2]. However, arrhythmia, infection, and possible pulmonary artery disruption have always been concerns related to the use of a PAC and led to a growing interest in the development of noninvasive hemodynamic monitoring devices [4–6]. One less invasive thermodilution-based technique consists of the pulse-induced cardiac output device (PiCCO) but exclusively ultrasound-based devices as the USCOM monitor are entirely non-invasive methods for measuring CO [7–13]. Beside accuracy and the method-related risks, another crucial criterion consists of the time required for the determination of CO [14]. USCOM is a feasible, continuous-wave Doppler-based method which noninvasively measures CO in a fast and economical way. The present study aimed at comparing the accuracy of the USCOM device with that of the thermodilution technique (PiCCO) in septic patients. 2. Materials and Methods Seventy adult, predominantly and mechanically ventilated, patients were investigated in this observational study. All patients suffered from septic
Comparison of uncalibrated arterial waveform analysis in cardiac surgery patients with thermodilution cardiac output measurements
Michael Sander, Claudia D Spies, Herko Grubitzsch, Achim Foer, Marcus Müller, Christian von Heymann
Critical Care , 2006, DOI: 10.1186/cc5103
Abstract: Data from 30 patients were analysed during this prospective study. COPAC, COTranspulm, and COWave were determined in all patients at four different time points prior, during, and after CABG surgery. The COPAC and the COTranspulm were measured by triple injection of 10 ml of iced isotone sodium chloride solution into the central venous line of the PAC. Measurements of COWave were simultaneously taken at these time points.The overall correlation showed a Spearman correlation coefficient between COPAC and COWave of 0.53 (p < 0.01) and 0.84 (p < 0.01) for COPAC and COTranspulm. Bland-Altman analysis showed a mean bias and LOAs of 0.6 litres per minute and -2.2 to +3.4 litres per minute for COPAC versus COWave and -0.1 litres per minute and -1.8 to +1.6 litres per minute for COPAC versus COTranspulm.Arterial waveform analysis with an uncalibrated algorithm COWave underestimated COPAC to a clinically relevant extent. The wide range of LOAs requires further evaluation. Better results might be achieved with an improved new algorithm. In contrast to this, we observed a better correlation of thermodilution COTranspulm and thermodilution COPAC measurements prior, during, and after CABG surgery.Advanced haemodynamic monitoring is indicated only in selected patients. In cardiac surgical patients, perioperative haemodynamic management is often guided by cardiac output (CO) measurement using the pulmonary artery catheter (PAC). The use of the PAC, however, has been decreasing over the last years in surgical and cardiac surgical patients as the benefit of guiding therapy is doubtful. Furthermore, its usage might even be associated with increased morbidity [1]. Other randomised studies did not provide clear evidence of benefit or harm by managing critically ill patients with a PAC [2,3]. Only some studies showed beneficial effect by guiding the therapy by PAC-derived data [4]. Therefore, alternative strategies have been developed to measure CO. Aortic transpulmonary thermodilution (
Lack of agreement between esophageal doppler cardiac output measurements and continuous pulse contour analysis during off-pump cardiac surgery
H. Paarmann,J. Fassl,H. Kiefer,J. Ender
Applied Cardiopulmonary Pathophysiology , 2010,
Abstract: Objective: Transesophageal echo-Doppler cardiac output as well as arterial pulse contour analyses cardiac output are increasingly used for cardiac output monitoring. No data are available whether both techniques may be used interchangeably in patients undergoing cardiac surgery. Design: Prospective, observational study Setting: Operating rooms of a university affiliated hospital. Patients: 30 patients undergoing elective coronary artery bypass grafting surgery.Interventions: NoneMeasurements: 900 paired cardiac output measurements were obtained by pulse contour analysis following transpulmonary thermodilution equilibration by the PiCCO system (PiCCO, Pulsion, Munich, Germany) and by the HemoSonic esophageal doppler monitor (HemoSonic 100; Arrow International, Reading, PA). Measurements were performed within the first hour after induction of anesthesia. Results: Bland-Altman analysis of the complete data set showed a mean difference (bias) of - 0.12 l/min (95% CI -0.06 to -0.18) with limits of agreement + 1.8 l/min to -1.6 l/min (upper 95% CI 1.78 to 1.98; lower 95% CI -1.74 to -1.54), the percentage error was + 37% to -44.5%. Transesophageal echo-Doppler cardiac output closely correlated (r = 0.75, p < 0.0001) with pulse-contour analyses cardiac output. Conclusions: Several studies have shown the accuracy of calibrated pulse contour cardiac output measurements in patients undergoing cardiac surgery. Thus, the present data question the reliability of transesophageal echo-Doppler derived cardiac output measurements in this setting and may have implications for using transesophageal echo-Doppler during goal-directed hemodynamic optimization.
Variations in arterial blood pressure are associated with parallel changes in FlowTrac/Vigileo?-derived cardiac output measurements: a prospective comparison study
Savvas Eleftheriadis, Zisis Galatoudis, Vasilios Didilis, Ioannis Bougioukas, Julika Sch?n, Hermann Heinze, Klaus-Ulrich Berger, Matthias Heringlake
Critical Care , 2009, DOI: 10.1186/cc8161
Abstract: Comparative measurements of cardiac output by FTV (derived from a femoral arterial line; software version 1.14) and IPATD were performed in 16 patients undergoing elective CABG in the period before institution of cardiopulmonary bypass. Measurements were performed after induction of anesthesia, after sternotomy, and during five time points during graft preparation. During graft preparation, arterial blood pressure was increased stepwise in intervals of 10 to 15 minutes by infusion of noradrenaline and lowered thereafter to baseline levels.Mean arterial blood pressure was varied between 85 mmHg and 115 mmHg. IPATD cardiac output did not show significant changes during periods with increased arterial pressure either during sternotomy or after pharmacological manipulation. In contrast, FTV cardiac output paralleled changes in arterial blood pressure; i.e. increased significantly if blood pressure was raised and decreased upon return to baseline levels. Mean arterial blood pressure (MAP) and FTV cardiac output were closely correlated (r = 0.63 (95% confidence interval [CI]: 0.49 - 0.74), P < 0.0001) while no correlation between MAP and IPATD cardiac output was observed. Bland-Altman analyses for FTV versus IPATD cardiac output measurements revealed a bias of 0.4 l/min (8.5%) and limits of agreement from 2.1 to -1.3 l/min (42.2 to -25.3%).Acute variations in arterial blood pressure alter the reliability of the FlowTrac/Vigileo? device with the second-generation software. This finding may help to explain the variable results of studies comparing the FTV system with other cardiac output monitoring techniques, questions the usefulness of this device for hemodynamic monitoring of patients undergoing rapid changes in arterial blood pressure, and should be kept in mind when using vasopressors during FTV-guided hemodynamic optimization.Autocalibrated pressure waveform analysis by the FlowTrac/Vigileo? (FTV) system allows determination of cardiac output (CO) from the arterial pr
Differences of cardiac output measurements by open-circuit acetylene uptake in pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension: a cohort study
Martin Schwaiblmair, Christian Faul, Wolfgang von Scheidt, Thomas M Berghaus
Respiratory Research , 2012, DOI: 10.1186/1465-9921-13-18
Abstract: Single-breath open-circuit C2H2 uptake, thermodilution, and cardiopulmonary exercise testing were performed in 72 PAH and 32 CTEPH patients.In PAH patients the results for cardiac output obtained by the two methods showed an acceptable agreement with a mean difference of -0.16 L/min (95% CI -2.64 to 2.32 L/min). In contrast, the agreement was poorer in the CTEPH group with the difference being -0.56 L/min (95% CI -4.96 to 3.84 L/min). Functional dead space ventilation (44.5 ± 1.6 vs. 32.2 ± 1.4%, p < 0.001) and the mean arterial to end-tidal CO2 gradient (9.9 ± 0.8 vs. 4.1 ± 0.5 mmHg, p < 0.001) were significantly elevated among CTEPH patients.Cardiac output evaluation by the C2H2 technique should be interpreted with caution in CTEPH, as ventilation to perfusion mismatching might be more relevant than in PAH.The assessment of cardiac output is a crucial factor in the risk stratification and management of patients with pulmonary hypertension (PH) as it is directly related to the clinical severity of the disease as well as being one of the most important prognostic factors [1].Several methods have been introduced to measure cardiac output in humans. The thermodilution technique has been validated against the direct Fick method, which represents the "gold standard" when evaluating cardiac output [2]. It is used routinely to assess cardiac output in PH patients. However, the thermodilution method is an invasive technique requiring right heart catheterization of the patient. A reliable non-invasive method to determine the cardiac output would allow serial measurements and, thus, would facilitate the follow-up management of PH patients. Among the non-invasive techniques the acetylene (C2H2) rebreathing method has been validated against different other techniques and has gained wide acceptance [2-4]. A drawback to the method, however, is the build-up of carbon dioxide (CO2) as a result of rebreathing. Therefore, open-circuit methods have been developed [5,6]. C2H2 is a non
Cardiac output monitoring: an integrative perspective
Jamal A Alhashemi, Maurizio Cecconi, Christoph K Hofer
Critical Care , 2011, DOI: 10.1186/cc9996
Abstract: The aim of this article is to provide a systematic update of the currently available and most commonly used cardiac output monitoring devices. In addition, an integrated approach for the use of these different devices in critically ill patients will be presented taking into consideration the devices' technical characteristics, their performance and typical limitations, and also any additional hemodynamic variables they may offer.When selecting a cardiac output monitoring device for clinical use, different factors play a role (Table 1): Institutional factors may largely limit the choice of the available devices. On the other hand important device-related factors, e.g., invasiveness (Figure 1), may restrict the area of application. Moreover, patient specific conditions may dictate the use of an invasive or a particular minimally-or non-invasive device.The PAC was the clinical standard for cardiac output monitoring for more than 20 years and the technique has been extensively investigated. Its complications are well known and despite developments in recent years, the PAC has a distinct role in patient care. An in-depth review is beyond the scope of this article, but some technical aspects and limitations need to be noted: Cardiac output measurement by intermittent pulmonary artery thermodilution, which is based on the Stewart-Hamilton principle, is considered to be the 'reference cardiac output monitoring standard' against which all new cardiac output measuring devices are compared. However, operator dependence, various patient conditions (e.g., mitral or tricuspid valve insufficiency, shunt) or misplacement of the PAC may influence reliable cardiac output assessment [6]. In contrast, continuous cardiac output assessment may overcome some of theselimitations. Intermittent thermal filament heating induces pulmonary artery temperature changes that are measured via a distal thermistor and matched with the input signal. Based on the cross correlation of in- and output sign
Why measure cardiac output?
Michael R Pinsky
Critical Care , 2002, DOI: 10.1186/cc1863
Abstract: Cardiac output is a primary determinant of global oxygen transport from the heart to the body. Also, because the major function of the cardiovascular system is to supply sufficient amounts of oxygen to meet the metabolic demands of the tissues, it appears reasonable to measure cardiac output in the assessment of cardiovascular insufficiency. Regrettably, numerous studies have shown that neither absolute values for cardiac output nor its change in response to therapy reflect the adequacy of local blood flow or outcome from critical illness [1,2]. Clearly, one may have a cardiac output within the normal range (e.g. 2.5 l/min per m2) and still be in circulatory shock if metabolic demand is increased or blood flow distribution is deranged. Treating septic shock patients with the goal of augmenting cardiac output to high levels (i.e. >3.5 l/min per m2) does not improve survival rates [3,4,5] and may actually increase mortality [6]. Thus, why measure cardiac output?Clearly, a very low cardiac output is detrimental. Critically ill patients who are unable to sustain a cardiac index in excess of 2 l/min per m2, despite aggressive therapy, have a very high mortality rate [4]. In many of these patients the cause of the low cardiac output is inadequate cardiac filling, which is responsive to fluid resuscitation. However, in patients with combined cardiac and respiratory disease, it is often difficult to assess the adequacy of resuscitation without measurement of cardiac output. Furthermore, a recent single center study of septic patients treated in an emergency department [7] documented that rapid early resuscitation with a goal of re-establishing adequate oxygen delivery resulted in a markedly reduced mortality and duration of hospital stay. Thus, at least in some patients, measurement of cardiac output is indicated as an aid to prognosis and diagnosis, and to monitor the adequacy of therapy.If it is useful to measure cardiac output, then it is also important that its measurem
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