Evaluation of the estimated continuous cardiac output monitoring system in adults and children undergoing kidney transplant surgery: a pilot study

Evaluation of the estimated continuous cardiac output (esCCO) allows non-invasive and continuous assessment of cardiac output. However, the applicability of this approach in children has not been assessed thus far. We compared the correlation coefficient, bias, standard deviation (SD), and the lower and upper 95 % limits of agreement for esCCO and dye densitography-cardiac output (DDG-CO) measurements by pulse dye densitometry (PDD) in adults and children. On the basis of these assessments, we aimed to examine whether esCCO can be used in pediatric patients. DDG-CO was measured by pulse dye densitometry (PDD) using indocyanine green. Modified-pulse wave transit time, obtained using pulse oximetry and electrocardiography, was used to measure esCCO. Correlations between DDG-CO and esCCO in adults and children were analyzed using regression analysis with the least squares method. Differences between the two correlation coefficients were statistically analyzed using a correlation coefficient test. Bland–Altman plots were used to evaluate bias and SD for DDG-CO and esCCO in both adults and children, and 95 % limits of agreement (bias ± 1.96 SD) and percentage error (1.96 SD/mean DDG-CO) were calculated and compared. The average age of the adult patients (n = 10) was 39.3 ± 12.1 years, while the average age of the pediatric patients (n = 7) was 9.4 ± 3.1 years (p < 0.001). For adults, the correlation coefficient was 0.756; bias, ?0.258 L/min; SD, 1.583 L/min; lower and upper 95 % limits of agreement for DDG-CO and esCCO, ?3.360 and 2.844 L/min, respectively; and percentage error, 42.7 %. For children, the corresponding values were 0.904; ?0.270; 0.908; ?2.051 and 1.510 L/min, respectively; and 35.7 %. Due to the high percentage error values, we could not establish a correlation between esCCO and DDG-CO. However, the 95 % limits of agreement and percentage error were better in children than in adults. Due to the high percentage error, we could not confirm a correlation between esCCO and DDG-CO. However, the agreement between esCCO and DDG-CO seems to be higher in children than in adults. These results suggest that esCCO can also be used in children. Future studies with bigger study populations will be required to further investigate these conclusions.     

The ability of a new continuous cardiac output monitor to measure trends in cardiac output following implementation of a patient information calibration and an automated exclusion algorithm

A new non-invasive continuous cardiac output (esCCO) monitoring system solely utilizing a routine cardiovascular monitor was developed, even though a reference cardiac output (CO) is consistently required. Subsequently, a non-invasive patient information CO calibration together with a new automated exclusion algorithm was implemented in the esCCO system. We evaluated the accuracy and trending ability of the new esCCO system. Either operative or postoperative data of a multicenter study in Japan for evaluation of the accuracy of the original version of esCCO system were used to develop the new esCCO system. A total of 207 patients, mostly cardiac surgical patients, were enrolled in the study. Data were manually reviewed to formulate a new automated exclusion algorithm with enhanced accuracy. Then, a new esCCO system based on a patient information calibration together with the automated exclusion algorithm was developed. CO measured with a new esCCO system was compared with the corresponding intermittent bolus thermodilution CO (ICO) utilizing statistical methods including polar plots analysis. A total of 465 sets of CO data obtained using the new esCCO system were evaluated. The difference in the CO value between the new esCCO and ICO was 0.34?±?1.50 (SD) L/min (95?% confidence limits of ?2.60 to 3.28?L/min). The percentage error was 69.6?%. Polar plots analysis showed that the mean polar angle was ?1.6° and radial limits of agreement were ±53.3°. This study demonstrates that the patient information calibration is clinically useful as ICO, but trending ability of the new esCCO system is not clinically acceptable as judged by percentage error and polar plots analysis, even though it’s trending ability is comparable with currently available arterial waveform analysis methods.     

Pulse-contour derived cardiac output measurements in morbid obesity: influence of actual,ideal and adjusted bodyweight

The non-invasive Nexfin cardiac output (CO) monitor shows a low level of agreement with the gold standard thermodilution method in morbidly obese patients. Here we investigate whether this disagreement is related to excessive bodyweight, and can be improved when bodyweight derivatives are used instead. We performed offline analyses of cardiac output recordings of patient data previously used and partly published in an earlier study by our group. In 30 morbidly obese patients (BMI?>?35 kg/m²) undergoing laparoscopic gastric bypass, cardiac output was simultaneously determined with PiCCO thermodilution and Nexfin pulse-contour method. We investigated if agreement of Nexfin-derived CO with thermodilution CO improved when ideal and adjusted—instead of actual- bodyweight were used as input to the Nexfin. Bodyweight correlated with the difference between Nexfin-derived and thermodilution-derived CO (r?=??0.56; p?=?0.001). Bland Altman analysis of agreement between Nexfin and thermodilution-derived CO revealed a bias of 0.4?±?1.6 with limits of agreement (LOA) from ?2.6 to 3.5 L min when actual bodyweight was used. Bias was ?0.6?±?1.4 and LOA ranged from ?3.4 to 2.3 L min when ideal bodyweight was used. With adjusted bodyweight, bias improved to 0.04?±?1.4 with LOA from ?2.8 to 2.9 L min. Our study shows that agreement of the Nexfin-derived with invasive CO measurements in morbidly obese patients is influenced by body weight, suggesting that Nexfin CO measurements in patients with a BMI above 35 kg/m² should be interpreted with caution. Using adjusted body weight in the Nexfin CO-trek algorithm reduced the bias.     

Evaluation of the use of the fourth version FloTrac system in cardiac output measurement before and after cardiopulmonary bypass

The FloTrac system is a system for cardiac output (CO) measurement that is less invasive than the pulmonary artery catheter (PAC). The purposes of this study were to (1) compare the level of agreement and trending abilities of CO values measured using the fourth version of the FloTrac system (CCO-FloTrac) and PAC-originated continuous thermodilution (CCO-PAC) and (2) analyze the inadequate CO-discriminating ability of the FloTrac system before and after cardiopulmonary bypass (CPB). Fifty patients were included. After exclusion, 32 patients undergoing cardiac surgery with CPB were analyzed. All patients were monitored with a PAC and radial artery catheter connected to the FloTrac system. CO was assessed at 10 timing points during the surgery. In the Bland–Altman analysis, the percentage errors (bias, the limits of agreement) of the CCO-FloTrac were 61.82% (0.16, ??2.15 to 2.47 L min) and 51.80% (0.48, ??1.97 to 2.94 L min) before and after CPB, respectively, compared with CCO-PAC. The concordance rates in the four-quadrant plot were 64.10 and 62.16% and the angular concordance rates (angular mean bias, the radial limits of agreement) in the polar-plot analysis were 30.00% (17.62°, ??70.69° to 105.93°) and 38.63% (??10.04°, ??96.73° to 76.30°) before and after CPB, respectively. The area under the receiver operating characteristic curve for CCO-FloTrac was 0.56, 0.52, 0.52, and 0.72 for all, ≥?±?5, ≥?±?10, and ≥?±?15% CO changes (ΔCO) of CCO-PAC before CPB, respectively, and 0.59, 0.55, 0.49, and 0.46 for all, ≥?±?5, ≥?±?10, and ≥?±?15% ΔCO of CCO-PAC after CPB, respectively. When CO <?4 L/min was considered inadequate, the Cohen κ coefficient was 0.355 and 0.373 before and after CPB, respectively. The accuracy, trending ability, and inadequate CO-discriminating ability of the fourth version of the FloTrac system in CO monitoring are not statistically acceptable in cardiac surgery.     

Comparison of the ability of two continuous cardiac output monitors to measure trends in cardiac output: estimated continuous cardiac output measured by modified pulse wave transit time and an arterial pulse contour-based cardiac output device

Estimated continuous cardiac output (esCCO), a noninvasive technique for continuously measuring cardiac output (CO), is based on modified pulse wave transit time, which in turn is determined by pulse oximetry and electrocardiography. However, its trending ability has never been evaluated in patients undergoing non-cardiac surgery. Therefore, this study examined esCCO’s ability to detect the exact changes in CO, compared with currently available arterial waveform analysis methods, in patients undergoing kidney transplantation. CO was measured using an esCCO system and arterial pressure-based CO (APCO), and compared with a corresponding intermittent bolus thermodilution CO (ICO) method. Percentage error and statistical methods, including concordance analysis and polar plot analysis, were used to analyze results from 15 adult patients. The difference in the CO values between esCCO and ICO was ?0.39 ± 1.15 L min^?1 (percentage error, 35.6 %). And corrected precision for repeated measures was 1.16 L min^?1 (percentage error for repeated measures, 36.0 %). A concordance analysis showed that the concordance rate was 93.1 %. The mean angular bias was ?1.8° and the radial limits of agreement were ±37.6°. The difference between the APCO and ICO CO values was 0.04 ± 1.37 L min^?1 (percentage error, 42.4 %). And corrected precision for repeated measures was 1.37 L min^?1 (percentage error for repeated measures, 42.5 %). The concordance rate was 89.7 %, with a mean angular bias of ?3.3° and radial limits of agreement of ±42.2°. This study demonstrated that the trending ability of the esCCO system is not clinically acceptable, as judged by polar plots analysis; however, its trending ability is clinically acceptable based on a concordance analysis, and is comparable with currently available arterial waveform analysis methods.     

Comparison of electrical velocimetry and cardiac magnetic resonance imaging for the non-invasive determination of cardiac output

A novel algorithm of impedance cardiography referred to as electrical velocimetry (EV) has been introduced for non-invasive determination of cardiac output (CO). Previous validation studies yielded diverging results and no comparison with the non-invasive gold standard cardiac magnetic resonance imaging (CMR) has been performed. We therefore aimed to prospectively assess the accuracy and reproducibility of EV compared to CMR. 152 consecutive stable patients undergoing CMR were enrolled. EV measurements were taken twice before or after CMR in supine position and averaged over 20 s (AESCULON^®, Osypka Medical, Berlin, Germany). Bland–Altman analysis showed insufficient agreement of EV and CMR with a mean bias of 1.2 ± 1.4 l/min (bias 23 ± 26 %, percentage error 51 %). Reproducibility was high with 0.0 ± 0.3 l/min (bias 0 ± 8 %, percentage error 15 %). Outlier analysis revealed gender, height, CO and stroke volume (SV) by CMR as independent predictors for larger variation. Stratification of CO_CMR in quintiles demonstrated a good agreement for low values (<4.4 l/min) with bias increasing significantly with quintile as high as 3.1 ± 1.1 l/min (p < 0.001). Reproducibility was not affected (p = 0.71). Subgroup analysis in patients with arrhythmias (p = 0.19), changes in thoracic fluid content (p = 0.51) or left heart failure (p = 0.47) could not detect significant differences in accuracy. EV showed insufficient agreement with CMR and good reproducibility. Gender, height and increasing CO and SV were associated with increased bias while not affecting reproducibility. Therefore, absolute values should not be used interchangeably in clinical routine. EV yet may find its place for clinical application with further investigation on its trending ability pending.     

An autocalibrating algorithm for non-invasive cardiac output determination based on the analysis of an arterial pressure waveform recorded with radial artery applanation tonometry: a proof of concept pilot analysis

We aimed to describe and evaluate an autocalibrating algorithm for determination of cardiac output (CO) based on the analysis of an arterial pressure (AP) waveform recorded using radial artery applanation tonometry (AT) in a continuous non-invasive manner. To exemplarily describe and evaluate the CO algorithm, we deliberately selected 22 intensive care unit patients with impeccable AP waveforms from a database including AP data obtained with AT (T-Line system; Tensys Medical Inc.). When recording AP data for this prospectively maintained database, we had simultaneously noted CO measurements obtained from just calibrated pulse contour analysis (PiCCO system; Pulsion Medical Systems) every minute. We applied the autocalibrating CO algorithm to the AT-derived AP waveforms and noted the computed CO values every minute during a total of 15 min of data recording per patient (3 × 5-min intervals). These 330 AT-derived CO (AT-CO) values were then statistically compared to the corresponding pulse contour CO (PC-CO) values. Mean ± standard deviation for PC-CO and AT-CO was 7.0 ± 2.0 and 6.9 ± 2.1 L/min, respectively. The coefficient of variation for PC-CO and AT-CO was 0.280 and 0.299, respectively. Bland–Altman analysis demonstrated a bias of +0.1 L/min (standard deviation 0.8 L/min; 95 % limits of agreement ?1.5 to 1.7 L/min, percentage error 23 %). CO can be computed based on the analysis of the AP waveform recorded with AT. In the selected patients included in this pilot analysis, a percentage error of 23 % indicates clinically acceptable agreement between AT-CO and PC-CO.     

A comparison of volume clamp method-based continuous noninvasive cardiac output (CNCO) measurement versus intermittent pulmonary artery thermodilution in postoperative cardiothoracic surgery patients

The CNAP technology (CNSystems Medizintechnik AG, Graz, Austria) allows continuous noninvasive arterial pressure waveform recording based on the volume clamp method and estimation of cardiac output (CO) by pulse contour analysis. We compared CNAP-derived CO measurements (CNCO) with intermittent invasive CO measurements (pulmonary artery catheter; PAC-CO) in postoperative cardiothoracic surgery patients. In 51 intensive care unit patients after cardiothoracic surgery, we measured PAC-CO (criterion standard) and CNCO at three different time points. We conducted two separate comparative analyses: (1) CNCO auto-calibrated to biometric patient data (CNCO_bio) versus PAC-CO and (2) CNCO calibrated to the first simultaneously measured PAC-CO value (CNCO_cal) versus PAC-CO. The agreement between the two methods was statistically assessed by Bland–Altman analysis and the percentage error. In a subgroup of patients, a passive leg raising maneuver was performed for clinical indications and we present the changes in PAC-CO and CNCO in four-quadrant plots (exclusion zone 0.5 L/min) in order to evaluate the trending ability of CNCO. The mean difference between CNCO_bio and PAC-CO was +0.5 L/min (standard deviation?±?1.3 L/min; 95% limits of agreement ?1.9 to +3.0 L/min). The percentage error was 49%. The concordance rate was 100%. For CNCOcal, the mean difference was ?0.3 L/min (±0.5 L/min; ?1.2 to +0.7 L/min) with a percentage error of 19%. In this clinical study in cardiothoracic surgery patients, CNCO_cal showed good agreement when compared with PAC-CO. For CNCO_bio, we observed a higher percentage error and good trending ability (concordance rate 100%).     

Continuous cardiac output measurement by un-calibrated pulse wave analysis and pulmonary artery catheter in patients with septic shock

Septic shock is a serious medical condition. With increased concerns about invasive techniques, a number of non-invasive and semi-invasive devices measuring cardiac output (CO) have become commercially available. The aim of the present study was to determine the accuracy, precision and trending abilities of the FloTrac and the continuous pulmonary artery catheter thermodilution technique determining CO in septic shock patients. Consecutive septic shock patients were included in two centres and CO was measured every 4 h up to 48 h by FloTrac (APCO) and by pulmonary artery catheter (PAC) using the continuous (CCO) and intermittent (ICO) technique. Forty-seven septic shock patients with 326 matched sets of APCO, CCO and ICO data were available for analysis. Bland and Altman analysis revealed a mean bias ±2 SD of 0.0 ± 2.14 L min^?1 for APCO–ICO (%error = 34.5 %) and 0.23 ± 2.55 L min^?1 for CCO–ICO (%error = 40.4 %). Trend analysis showed a concordance of 85 and 81 % for APCO and CCO, respectively. In contrast to CCO, APCO was influenced by systemic vascular resistance and by mean arterial pressure. In septic shock patients, APCO measurements assessed by FloTrac but also the established CCO measurements using the PAC did not meet the currently accepted statistical criteria indicating acceptable clinical performance.     

Determination of cardiac output with dynamic contrast-enhanced computed tomography

Cardiac output (CO) is an important diagnostic and prognostic factor in the haemodynamic evaluation of patients. The gold standard for CO measurement, thermodilution, requires an invasive right-heart catheterisation (RHC). In this pilot study we aimed to determine the accuracy of non-invasive CO determination from dynamic contrast-enhanced computed tomography (CT) compared to thermodilution. Patients who underwent diagnostic or follow-up RHC due to suspected or known pulmonary vascular disease at our department and required a thoracic CT between June 2011 and August 2012 were included. CO was determined from CT attenuation-time curves in the pulmonary artery and the ascending aorta using a dynamic contrast-enhanced CT sequence. CO determined in N = 18 patients by dynamic CT in the pulmonary artery was in very good agreement with thermodilution data (r = 0.84). Bland–Altman analysis showed a systematic overestimation of 0.7 ± 0.6 l/min compared to thermodilution. Data from the ascending aorta also showed a good correlation, but with a larger scattering of the values. The average effective dose for the dynamic investigation was 1.2 ± 0.7 mSv. CO determined with dynamic contrast-enhanced CT in the main pulmonary artery reliably predicts the values obtained by thermodilution during RHC. This non-invasive technique might provide an alternative for repeated invasive right-heart catheter investigations in the follow-up of pulmonary arterial hypertension patients.     

Reliability of cardiac output measurements using LiDCOrapid™ and FloTrac/Vigileo™ across broad ranges of cardiac output values

Knowing a patient’s cardiac output (CO) could contribute to a safe, optimized hemodynamic control during surgery. Precise CO measurements can serve as a guide for resuscitation therapy, catecholamine use, differential diagnosis, and intervention during a hemodynamic crisis. Despite its invasiveness and intermittent nature, the thermodilution technique via a pulmonary artery catheter (PAC) remains the clinical gold standard for CO measurements. LiDCOrapid? (LiDCO, London, UK) and FloTrac/Vigileo? (Edwards Lifesciences, Irvine, CA) are less invasive continuous CO monitors that use arterial waveform analysis. Their calculations are based on arterial waveform characteristics and do not require calibration. Here, we evaluated LiDCOrapid? and FloTrac/Vigileo? during off-pump coronary artery bypass graft (OPCAB) and living-donor liver transplantation (LDLT) surgery. This observational, single-center study included 21 patients (11 OPCAB and 10 LDLT). We performed simultaneous measurements of CO at fixed sampling points during surgery using both devices (LiDCOrapid? version 1.04-b222 and FloTrac/Vigileo? version 3.02). The thermodilution technique via a PAC was used to obtain the benchmark data. LiDCOrapid? and FloTrac/Vigileo? were used in an uncalibrated fashion. We analyzed the measured cardiac index using a Bland–Altman analysis (the method of variance estimates recovery), a polar plot method (half-moon method), a 4-quadrant plot and compared the widths of the limits of agreement (LOA) using an F test. One OPCAB patient was excluded because of the use of an intra-aortic balloon pumping during surgery, and 20 patients (10 OPCAB and 10 LDLT) were ultimately analyzed. We obtained 149 triplet measurements with a wide range of cardiac index. For the FloTrac/Vigileo?, the bias and percentage error were ?0.44 L/min/m² and 74.4 %. For the LiDCOrapid?, the bias and percentage error were ?0.38 L/min/m² and 53.5 %. The polar plot method showed an angular bias (FloTrac/Vigileo? vs. LiDCOrapid?: 6.6° vs. 5.8°, respectively) and radial limits of agreement (?63.9 to 77.1 vs. ?41.6 to 53.1). A 4-quadrant plot was used to obtain concordance rates (FloTrac/Vigileo? vs. PAC and LiDCOrapid? vs. PAC: 84.0 and 92.4 %, respectively). We could compare CO measurement devices across broad ranges of CO and SVR using LDLT and OPCAB surgical patients. An F test revealed no significant difference in the widths of the LoA for both devices when sample sizes capable of detecting a more than two-fold difference were used. We found that both devices tended to underestimate the calculated CIs when the CIs were relatively high. These proportional bias produced large percentage errors in the present study.     

Isocapnic hyperpnea with a portable device in Cystic Fibrosis: an agreement study between two different set-up modalities

To evaluate the bias and precision of the respiratory muscle training device formulas to predict respiratory minute volume (RMV) and volume of the reservoir bag (BV) on a cohort of subjects with Cystic Fibrosis (CF). CF patients with available pulmonary function tests and maximal voluntary manoeuvres were included in the study. Vital capacity and maximal voluntary ventilation were extracted from subjects’ records and then inserted to the manufacturer’s formulas to obtain RMV and BV (measured setting). RMV and BV were compared according to standard and measured formulas in males and females. Sample was described and then processed using Bland–Altman analysis. Bland–Altman analysis for RMV revealed a bias and precision of 8.8 ± 29 L/min in males and 28.8 ± 16 L/min in females; 0.4 ± 0.5 L in males and 0.7 ± 0.4 L in females for BV. Concordance correlation coefficients for RMV were ?0.03 in males and 0.02 in females; 0.22 in males and 0.03 in females for BV, reinforcing an unsatisfactory concordance between measured and manufacturer setting. This study shows considerable discrepancies between the two methods, making the degree of agreement not clinically acceptable. This might cause inappropriate setting and disservice to patients with CF.     

Comparison of cardiac output measures by transpulmonary thermodilution,pulse contour analysis,and pulmonary artery thermodilution during off-pump coronary artery bypass surgery: a subgroup analysis of the cardiovascular anaesthesia registry at a single tertiary centre

Cardiac output measurement has a long history in haemodynamic management and many devices are now available with varying levels of accuracy. The purpose of the study was to compare the agreement and trending abilities of cardiac output, as measured by transpulmonary thermodilution and calibrated pulse contour analysis, using the VolumeView? system, continuous thermodilution via a pulmonary artery catheter, and uncalibrated pulse contour analysis, using FloTrac? with pulmonary artery bolus thermodilution. Twenty patients undergoing off-pump coronary artery bypass surgery using a pulmonary artery catheter and the VolumeView? and FloTrac? systems were included in this subgroup analysis of the cardiovascular anaesthesia registry at a single tertiary centre. During surgery, cardiac output was assessed after the induction of anaesthesia, after sternotomy, during the harvesting of grafts, during revascularization of the anterior and posterior/lateral wall, after protamine infusion, and after sternal fixation. In total, 145 sets of measurements were evaluated using Bland–Altman with % error calculation, correlation, concordance, and polar plot analyses. The percentage error (bias, limits of agreement) was 12.6 % (?0.12, ?0.64 to 0.41 L/min), 26.7 % (?0.38, ?1.50 to 0.74 L/min), 29.3 % (?0.08, ?1.32 to 1.15 L/min), and 33.8 % (?0.05, ?1.47 to 1.37 L/min) for transpulmonary thermodilution, pulmonary artery continuous thermodilution, calibrated, and uncalibrated pulse contour analysis, respectively, compared with pulmonary artery bolus thermodilution. All pairs of measurements showed significant correlations (p < 0.001), whereas only transpulmonary thermodilution revealed trending ability (concordance rate of 95.1 %, angular bias of 1.33°, and radial limits of agreement of 28.71°) compared with pulmonary artery bolus thermodilution. Transpulmonary thermodilution using the VolumeView? system provides reliable data on cardiac output measurement and tracking the changes thereof when compared with pulmonary artery bolus thermodilution in patients with preserved cardiac function during off-pump coronary artery bypass surgery. Trial registration NCT01713192 (ClinicalTrials.gov).     

Influence of different infracardial positions of central venous catheters in hemodynamic monitoring using the transpulmonal thermodilution method

Hemodynamic measurements are often conducted by the transpulmonary thermodilution (TPTD)-based PiCCO^®-system. This requires a central-venous (CVC) and a thermistor-tipped arterial catheter, usually placed in the femoral artery. In certain clinical situations, CVC devices have to be placed in the inferior vena cava. However, little is known about the influence of different CVC positions (i.e. ipsi- vs. contra-lateral to the arterial catheter) on the accuracy of the TPTD measurement results. In this prospective observational study surgical intensive care unit patients who had been inserted with CVCs either into the superior (CVC_VCS) or the inferior vena cava (CVC_inf) in addition to an arterial PiCCO^®-catheter, were enrolled. Patients were then divided into two groups: Group I was provided with a CVC in the contralateral (CVC_contra) and Group II in the ipsilateral (CVC_ipsi) inferior vena cava. Thermodilution via injection of ice-cold saline was then performed via CVC_sup and CVC_inf. Bland–Altman analysis for cardiac index (CI), extra-vascular lung water index (EVLWI) and global end-diastolic volume index (GEDVI) were employed. Additional correction formulas for femorally assed parameters were determined. In a total of 28 patients, bias (limits of agreement) for measurements of CI in CVC_contra was found to be +0.2 (?0.4; +0.9) and +0.3 (?0.4; +1.0) L/min/m² in CVC_ipsi. GEDVI showed a bias of +274.8 (?47.3; +596.9) mL/m² in CVC_contra and +274.7 (?100.7; +650.1) mL/m² in CVC_ipsi. The mean EVLWI were 9.4 ± 4.3 mL/kg for EVLWI_VCS and 10.7 ± 5.2 mL/kg for EVLWI_inf. The LoA yielded at ?3.4 and +6.1 mL/kg with a bias of +1.3 mL/kg. Percentage errors revealed clinically acceptable limits for CI and GEDVI, but not for EVLWI. Using TPTD via an infracardial central vein, measurements of CI showed high accuracy and precision while GEDVI measurements were precise with a lower accuracy, irrespective of the position of the infracardial CVC.     

The effect of head up tilting on bioreactance cardiac output and stroke volume readings using suprasternal transcutaneous Doppler as a control in healthy young adults

To compare the performance of a bioreactance cardiac output (CO) monitor (NICOM) and transcutaneous Doppler (USCOM) during head up tilting (HUT). Healthy young adult subjects, age 22 ± 1 years, 7 male and 7 female, were tilted over 3–5 s from supine to 70° HUT, 30° HUT and back to supine. Positions were held for 3 min. Simultaneous readings of NICOM and USCOM were performed 30 s into each new position. Mean blood pressure (MBP), heart rate (HR), CO and stroke volume (SV), and thoracic fluid content (TFC) were recorded. Bland–Altman, percentage changes and analysis of variance for repeated measures were used for statistical analysis. Pre-tilt NICOM CO and SV readings (6.1 ± 1.0 L/min and 113 ± 25 ml) were higher than those from USCOM (4.1 ± 0.6 L/min and 77 ± 9 ml) (P < 0.001). Bland–Altman limits of agreement for CO were wide with a percentage error of 38 %. HUT increased MBP and HR (P < 0.001). CO and SV readings decreased with HUT. However, the percentage changes in USCOM and NICOM readings did not concur (P < 0.001). Whereas USCOM provided gravitational effect proportional changes in SV readings of 23 ± 15 % (30° half tilt) and 44 ± 11 % (70° near full tilt), NICOM changes did not being 28 ± 10 and 33 ± 11 %. TFC decreased linearly with HUT. The NICOM does not provide linear changes in SV as predicted by physiology when patients are tilted. Furthermore there is a lack of agreement with USCOM measurements at baseline and during tilting.     

Cross-comparisons of trending accuracies of continuous cardiac-output measurements: pulse contour analysis,bioreactance, and pulmonary-artery catheter

We compared the similarity of cardiac-output (CO) estimates between available bolus thermodilution pulmonary-artery catheters (PAC), arterial pulse-contour analysis (LiDCOplus^?, FloTrac^? and PiCCOplus^?), and bioreactance (NICOM^?). Repetitive simultaneous estimates of CO obtained from the above devices were compared in 21 cardiac-surgery patients during the first 2 h post-surgery. Mean and absolute values for CO across the devices were compared by ANOVA, Bland–Altman, Pearson moment, and linear-regression analyses. Twenty-one simultaneous CO measurements were made before and after therapeutic interventions. Mean PAC CO (5.7?±?1.5 L min) was similar to LiDCO^?, FloTrac^?, PiCCO^?, and NICOM^? CO (6.0?±?1.9, 5.9?±?1.0, 5.7?±?1.8, 5.3?±?1.0 L min, respectively). Mean CO bias between each paired method was ?0.10 (PAC–LiDCO), 0.18 (PAC–PiCCO), ?0.40 (PAC–FloTrac), ?0.71 (PAC–NICOM), 0.28 (LiDCO–PiCCO), 0.39 (LiDCO–FloTrac), ?0.97 (NICOM–LiDCO), 0.61 (PiCCO–FloTrac), ?1.0 (NICOM–FloTrac), ?0.73 (NICOM–PiCCO) L/min, with limits of agreement (1.96 SD, ±95% CI) of ±?2.01, ±2.35, ±2.27, ±2.70, ±1.97, ±2.17, ±3.51, ±2.87, ±2.40, and ±?3.14 L min, respectively, and the percentage error for each of the paired devices was 35, 41, 40, 47, 33, 36, 59, 50, 42, and 55%, respectively. From Pearson moment analysis, dynamic changes in CO, estimated by each device, showed good cross-correlations. Although all devices studied recorded similar mean CO values, which dynamically changed in similar directions, they have markedly different bias and precision values relative to each other. Thus, results from prior studies that have used one device to estimate CO cannot be used to validate others devices.     

Transesophageal Doppler reliably tracks changes in cardiac output in comparison with intermittent pulmonary artery thermodilution in cardiac surgery patients

In this study a comparison of cardiac output (CO) measurements obtained with CardioQ transesophageal Doppler (TED) and pulmonary artery catheter (PAC) thermodilution (TD) technique was done in a systematic set-up, with induced changes in preload, afterload and heart rate. Twenty-five patients completed the study. Each patient were placed in the following successive positions: (1) supine, (2) head-down tilt, (3) head-up tilt, (4) supine, (5) supine with phenylephrine administration, (6) pace heart rate 80 beats per minute (bpm), (7) pace heart rate 110 bpm. The agreement of compared data was investigated by Bland–Altman plots, and to assess trending ability a four quadrants plot and a polar plot were constructed. Both methods showed an acceptable precision 6.4 % (PAC TD) and 12.8 % (TED). In comparison with PAC TD, the TED was associated with a mean bias in supine position of ?0.30 l min^?1 (95 % CI ?0.88; 0.27), wide limits of agreement, a percentage error of 69.5 %, and a trending ability with a concordance rate of 92 %, angular bias of 1.1° and a radial sector size of 40.0° corresponding to an acceptable trending ability. In comparison with PAC TD, the CardioQ TED showed a low mean bias, wide limits of agreement and a larger percentage error than should be expected from the precision of the two methods. However, an acceptable trending ability was found. Thus, the CardioQ TED should not replace CO measurements done by PAC TD, but could be a valuable tool in guiding therapy.     

Continuous noninvasive cardiac output determination using the CNAP system: evaluation of a cardiac output algorithm for the analysis of volume clamp method-derived pulse contour

The CNAP system (CNSystems Medizintechnik AG, Graz, Austria) provides noninvasive continuous arterial pressure measurements by using the volume clamp method. Recently, an algorithm for the determination of cardiac output by pulse contour analysis of the arterial waveform recorded with the CNAP system became available. We evaluated the agreement of the continuous noninvasive cardiac output (CNCO) measurements by CNAP in comparison with cardiac output measurements invasively obtained using transpulmonary thermodilution (TDCO). In this proof-of-concept analysis we studied 38 intensive care unit patients from a previously set up database containing CNAP-derived arterial pressure data and TDCO values obtained with the PiCCO system (Pulsion Medical Systems SE, Feldkirchen, Germany). We applied the new CNCO algorithm retrospectively to the arterial pressure waveforms recorded with CNAP and compared CNCO with the corresponding TDCO values (criterion standard). Analyses were performed separately for (1) CNCO calibrated to the first TDCO (CNCO-cal) and (2) CNCO autocalibrated to biometric patient data (CNCO-auto). We did not perform an analysis of trending capabilities because the patients were hemodynamically stable. The median age and APACHE II score of the 22 male and 16 female patients was 63 years and 18 points, respectively. 18 % were mechanically ventilated and in 29 % vasopressors were administered. Mean ± standard deviation for CNCO-cal, CNCO-auto, and TDCO was 8.1 ± 2.7, 6.4 ± 1.9, and 7.8 ± 2.4 L/min, respectively. For CNCO-cal versus TDCO, Bland–Altman analysis demonstrated a mean difference of +0.2 L/min (standard deviation 1.0 L/min; 95 % limits of agreement ?1.7 to +2.2 L/min, percentage error 25 %). For CNCO-auto versus TDCO, the mean difference was ?1.4 L/min (standard deviation 1.8 L/min; 95 % limits of agreement ?4.9 to +2.1 L/min, percentage error 45 %). This pilot analysis shows that CNCO determination is feasible in critically ill patients. A percentage error of 25 % indicates acceptable agreement between CNCO-cal and TDCO. The mean difference, the standard deviation, and the percentage error between CNCO-auto and TDCO were higher than between CNCO-cal and TDCO. A hyperdynamic cardiocirculatory state in a substantial number of patients and the hemodynamic stability making trending analysis impossible are main limitations of our study.     

Importance of re-calibration time on pulse contour analysis agreement with thermodilution measurements of cardiac output: a retrospective analysis of intensive care unit patients

We assessed the effect of re-calibration time on cardiac output estimation and trending performance in a retrospective analysis of an intensive care unit patient population using error grid analyses. Paired thermodilution and arterial blood pressure waveform measurements (N = 2141) from 222 patient records were extracted from the Multiparameter Intelligent Monitoring in Intensive Care II database. Pulse contour analysis was performed by implementing a previously reported algorithm at calibration times of 1, 2, 8 and 24 h. Cardiac output estimation agreement was assessed using Bland–Altman and error grid analyses. Trending was assessed by concordance and a 4-Quadrant error grid analysis. Error between pulse contour and thermodilution increased with longer calibration times. Limits of agreement were ?1.85 to 1.66 L/min for 1 h maximum calibration time compared to ?2.70 to 2.41 L/min for 24 h. Error grid analysis resulted in 74.2 % of points bounded by 20 % error limits of thermodilution measurements for 1 h calibration time compared to 65 % for 24 h. 4-Quadrant error grid analysis showed <75 % of changes in pulse contour estimates to be within ±80 % of the change in the thermodilution measurement at any calibration time. Shorter calibration times improved the agreement of cardiac output pulse contour estimates with thermodilution. Use of minimally invasive pulse contour methods in intensive care monitoring could benefit from prospective studies evaluating calibration protocols. The applied pulse contour analysis method and thermodilution showed poor agreement to monitor changes in cardiac output.     

The impact of systemic vascular resistance on the accuracy of the FloTrac/Vigileo™ system in the perioperative period of cardiac surgery: a prospective observational comparison study

FloTrac/Vigileo? system is based on arterial pressure waveform analysis arterial pressure-based CO (APCO). Therefore, systemic vascular resistance (SVR) can influence the accuracy of APCO. The purpose of this study is to evaluate the relationship between SVR and the accuracy of APCO. We managed 50 consecutive patients in the perioperative period of cardiac surgery with FloTrac/Vigileo? system (v. 3.02) and Swan–Ganz catheter/Vigilance? system pulmonary artery catheter-based CO (PAC-CO) simultaneously. Continuous hemodynamic measurement using both methods was performed every 20 s from the induction of anesthesia to PAC removal 4 h after extubation. A total of 11,092 (intraoperative), 38,455 (postoperative, pre-extubation), and 44,235 (postoperative, post-extubation) data pairs were finally analyzed. Bland–Altman analysis revealed that in the intraoperative [postoperative pre-extubation, post-extubation] period, the bias was 0.5 [0.1, 0.0] L/min and the limits of agreement ranged from ?2.4 to 3.3 [?2.2 to 2.4, ?2.4 to 2.3] L/min. The percentage error was 60.3 [54.5, 48.5] %. Regression analysis of the systemic vascular resistance index (SVRI) and the bias between APCO and PAC-CO showed that the bias was positively correlated to the SVRI. Subanalysis based on SVR with Lin’s concordance correlation coefficient revealed that relatively satisfactory concordance was found in the normal-SVR group (concordance correlation coefficient ρ _c = 0.51–0.56) regardless of vasoactive agent use. The accuracy of the FloTrac/Vigileo? System (v. 3.02) is relatively satisfactory in the condition with normal SVR regardless of vasoactive agent use. Positive correlation between the bias and SVR can be the clue to the more effective use of FloTrac/Vigileo? system.