Multi-channel electrical bioimpedance: a non-invasive method to simultaneously measure cardiac output and individual arterial limb flow in patients with cardiovascular disease

Background  Cardiac output is the fundamental determinant of peripheral blood flow however; optimal regional tissue perfusion is ultimately dependant on the integrity of the arterial conduits that transport flow. A complete understanding of tissue perfusion requires knowledge of both cardiac and peripheral blood flow. Existing noninvasive devices do not simultaneously assess the cardiac and peripheral circulations. Multi-channel electrical bioimpedance (MEB) measures cardiac output and peripheral flow simultaneously. Objectives  Assessment of the accuracy of MEB to measure cardiac output in patients with clinical heart failure (group 1) and to measure regional arterial limb flow in patients with exertional leg pain clinically thought to have peripheral arterial disease (group 2). Methods  Cardiac output was measured by MEB in 44 patients with moderate to severe clinical heart failure (group 1) and was compared to a cardiac output measured by 2D-Echo Doppler. Peripheral blood flow (regional ankle and arm flow) was measured by MEB in another group of 25 patients with exertional leg pain clinically thought to be claudication (group 2). The MEB ankle/arm flow ratio (AAI index) was then compared to a conventional ankle/brachial pressure ratio (ABI index). Results  There was excellent correlation between the mean cardiac index by MEB (2.01 l/min/m²) and by 2D-Echo Doppler (2.06 l/min/m²) and bias and precision was 0.05 (2.4%) and ±0.48 l/min/m² (±23%), respectively. The correlation was maintained for each measurement over a wide range of cardiac indices. There was good correlation between AAI and ABI measurements (P < 0.05). Conclusions   MEB accurately measures cardiac output in patients with moderate to severe clinical heart failure and accurately measures regional arterial limb flow in patients with peripheral arterial disease. Stanley AWH, Herald JW, Athanasuleas CL, Jacob SC, Bartolucci AA, Tsoglin AN. Multi-channel electrical bioimpedance: a non-invasive method to simultaneously measure cardiac output and individual arterial limb flow in patients with cardiovascular disease     

肺部超声与脉搏指示连续心排血量监测评价急性心力衰竭患者肺水肿程度

目的 对比肺部超声与脉搏指示连续心排血量监测（PiCCO）评价急性心力衰竭肺水肿的价值。方法 对11例急性心力衰竭患者先后行常规超声心动图、肺部超声及PiCCO,共获得26例/次数据,将其分为轻度组[血管外肺水指数（EVLWI）≤ 10 ml/kg,n=12]和重度组（EVLWI>10 ml/kg,n=14）,比较组间血清N末端B型脑钠肽前体（NT-proBNP）值、超声及PiCCO参数的差异。采用Spearman相关性分析各指标与EVLWI的相关性;绘制受试者工作特征（ROC）曲线,计算曲线下面积（AUC）,判断各指标评价肺水肿的效能。结果 轻度组舒张压及左心室射血分数（LVEF）明显高于重度组（P均<0.05）;NT-proBNP、心率、左心室舒张末期内径（LVEDD）、左心室收缩末期内径（LVESD）、肺动脉压（PAP）、下腔静脉直径（IVCD）、E/e''、B线总分、全心舒张末期容积指数（GEDVI）及EVLWI明显低于重度组（P均<0.05）。B线总分与EVLWI呈显著正相关（r=0.955,P<0.001）;其诊断EVLWI>10 ml/kg的AUC为0.95,截断值为15.00时,敏感度为92.90%,特异度为66.70%。结论 肺部超声可较准确地评价急性心力衰竭患者肺水肿程度;B线总分与EVLWI呈显著性相关。     

胸腔阻抗法对乌拉地尔治疗心力衰竭血流动力学变化的观察

目的：观察胸腔阻抗法对乌拉地尔治疗心力衰竭(心衰)的血流动力学变化。方法：16只健康杂种犬麻醉后，制成心衰模型。分为乌拉地尔组和生理盐水对照组，分别于用药前及用药后15、30、60、90和120min用无创血流动力学监测仪测定心率(HR)、每搏量(SV)、心排血量(CO)、射血前时间(PEP)、左室射血时间(LVET)、收缩时间比率(STR，PEP／LVET)、等容舒张时间(IRT)、肺毛细血管楔压(PCWP)、左室舒张末压(LVEI)P)、总外周阻力(TPR)、每搏左室作功(SW)和每分左室作功(CW)。结果：乌拉地尔较对照组明显增加CO和SV，缩短PEP和STR，降低PCWP、LVEDP和TPR，增加SW和CW，而对HR、LVET和IRT无影响。结论：胸腔阻抗法可作为无创、实时和准确的监测方法观察心衰治疗的血流动力学变化；乌拉地尔可以明显降低心脏前后负荷，增加CO和心肌收缩能力，具有改善心功能的作用。     

Phenotyping the Right Ventricle in Patients with Pulmonary Hypertension

Right ventricular (RV) failure is associated with poor outcomes in pulmonary hypertension (PH). We sought to phenotype the RV in PH patients with compensated and decompensated RV function by quantifying regional and global RV structural and functional changes. Twenty‐two patients (age 51 ± 11, 14 females, mean pulmonary artery (PA) pressure range 13–79 mmHg) underwent right heart catheterization, echocardiography, and ECG‐gated multislice computed tomography of the chest. Patients were divided into three groups: Normal, PH with hemodynamically compensated, and decompensated RV function (PH‐C and PH‐D, respectively). RV wall thickness (WT) was measured at end‐diastole (ED) and end‐systole (ES) in three regions: infundibulum, lateral free wall, and inferior free wall. Globally, RV volumes progressively increased from Normal to PH‐C to PH‐D and RV ejection fraction decreased. Regionally, WT increased and fractional wall thickening (FWT) decreased in a spatially heterogeneous manner. Infundibular wall stress was elevated and FWT was lower regardless of the status of global RV function. In PH, there are significant phenotypic abnormalities in the RV even in the absence of overt hemodynamic RV decompensation. Regional changes in RV structure and function may be early markers of patients at risk for developing RV failure.     

Elevated estimated pulmonary artery systolic pressure is associated with an adverse clinical outcome in patients receiving cardiac resynchronization therapy

BACKGROUND: A substantial percentage of patients with heart failure remain nonresponsive to cardiac resynchronization therapy (CRT). There is a paucity of information on the impact of baseline elevated pulmonary artery pressure on clinical outcome and on left ventricular reverse remodeling (LV-RR) after CRT. We sought to investigate the impact of elevated estimated pulmonary artery systolic pressure (ePASP) on clinical outcome and LV-RR after CRT. METHODS: This study retrospectively analyzed data from 68 subjects with standard indications for CRT over a 12-month period. Subjects were stratified into two groups based on the echocardiographic estimation of pulmonary artery pressure i.e., ePASP > or = 50 mmHg (n = 27) and ePASP < 50 mmHg (n = 41). Long-term response was measured as a combined endpoint of heart failure hospitalizations and all cause mortality at 12 months, and compared within the two groups using the Kaplan-Meier method. Follow up echocardiograms to assess for LV-RR were available in 51 subjects (mean duration 7.1 months). LV-RR was defined as any improvement in global systolic function with reduction in left ventricular internal diameter. RESULTS: The study population was composed of 24 women and 44 men (age, mean +/- SD; 70 +/- 11 years), with a decreased left ventricular ejection fraction ([25 +/- 9]%) and a wide QRS (171 +/- 54 ms). There were no significant differences in the clinical features between the high and low ePASP group. Subjects with ePASP > or = 50 mmHg had a significantly worse clinical outcome (Hazard ratio (95% CI), 2.0 (1.2-5.5), P = 0.02). Baseline ePASP was not predictive of LV-RR (P = 0.32). CONCLUSION: In patients receiving CRT, although elevated estimated pulmonary artery systolic pressure (ePASP > or = 50 mmHg) does not significantly impact LV reverse remodeling, it is associated with an adverse long-term outcome.     

Cardiovascular effects of ephedrine,caffeine and yohimbine measured by thoracic electrical bioimpedance in obese women

Low caloric diet is a commonly accepted treatment in obesity. However, owing to moderate results, a pharmacological support has been proposed. As some efficacious drugs activate overall sympathetic activity, they might modify functions of the cardiovascular system. Three groups of subjects were studied: (1) nine obese women receiving only a standard hypocaloric diet; (2) nine obese women receiving a standard hypocaloric diet and ephedrine (2 × 25 mg) with caffeine (2 × 200 mg); (3) nine obese women receiving a standard hypocaloric diet and ephedrine (2 × 25 mg) with caffeine (2 × 200 mg) and yohimbine (2 × 5 mg). The cardiovascular state was evaluated by thoracic electrical bioimpedance, automatic sphygmomanometry and continuous ECG recording. In each patient, the haemodynamic study was performed twice: at rest, i.e. before treatment; and after 10 days of treatment. On the same days in each patient, the haemodynamic tests were performed during physical exercises (handgrip stress and cycloergometer exercise). Caffeine and ephedrine had no haemodynamic effect in resting patients. These two drugs led to an increase in ejection fraction during cycloergometer exercise. Addition of yohimbine increased diastolic pressure and heart rate but decreased ejection fraction and stroke index during rest. We also observed that addition of yohimbine decreased ejection fraction during the handgrip and cycloergometer exercise and increased cardiac load during dynamic exercise. Pharmacological supplement of ephedrine and caffeine to a low caloric diet modified the cardiovascular system weakly, but the addition of yohimbine to this regimen attenuated cardiac performance during rest and handgrip and increased cardiac work during dynamic exercise.     

Non-invasive measurement of cardiac output: whole-body impedance cardiography in simultaneous comparison with thermodilution and direct oxygen Fick methods

Objective: To determine the reliability of whole-body impedance cardiography (ICG_WB), with electrodes attached to wrists and ankles, in the measurement of cardiac output (CO) on the basis of simultaneous comparison with thermodilution (TD) and direct oxygen Fick (Fick) methods. Design: Prospective clinical study. Setting: A surgical intensive care unit at a university hospital. Patients: Thirty consecutive subjects undergoing a coronary artery bypass surgery were investigated preoperatively. Measurements: ICG_WB derived CO was measured simultaneously with the TD and Fick methods to establish the biases and limits of agreement (LA) between the methods. Results: The results obtained by ICG_WB and the invasive methods showed good agreement. The bias and LA between CO_TD and CO_ICG were 0.00 l/min; –1.37 and 1.37 l/min, respectively, and were close to those obtained between CO_TD and CO_FICK, 0.32 l/min; 1.74 and –1.10 l/min. The bias and LA between the CO_FICK and CO_ICG were –0.32 l/min; –2.24 and 1.60 l/min respectively. The repeatability value of consecutive single measurements for ICG_WB (RV_ICG = 0.57 l/min) was much better than for the TD method (RV_TD = 1.10 l/min). Conclusion: There was close agreement between the results of the three methods in the measurement of CO. In sedated preoperative patients the accuracy of ICG_WB is within clinically acceptable limits and its repeatability is excellent. ICG_WB provides a useful alternative to the TD and Fick methods in cases where the pressures supplied by the pulmonary artery catheter are not essential. Received: 19 February 1997 Accepted: 14 August 1997     

Pulmonary arterial thermodilution, femoral arterial thermodilution and bioreactance cardiac output monitoring in a pediatric hemorrhagic hypovolemic shock model

Aim

Bioreactance is a new non-invasive method for cardiac output measurement (NICOM). There are no studies that have analysed the utility of this technique in a pediatric animal model of hemorrhagic shock.

Methods

A prospective study was performed using 9 immature Maryland pigs weighing 9 to 12 kg was performed. A Swan-Ganz catheter, a PiCCO catheter and 4 dual surface electrodes were placed at the four corners of the anterior thoracic body surface. Shock was induced by withdrawing a blood volume of 30 mL/kg, and then after, 30 mL/kg of Normal saline was administered. Seven simultaneous measurements of cardiac index (CI) were made by pulmonary artery thermodilution (PATD), Femoral artery thermodilution (FATD), and NICOM before, during, and after hypovolaemia and during and after volume expansion.

Results

The mean difference (bias) of differences (limits of agreement) between PATD and FATD was 0.84 (−1.87-3.51) L/min/1.77 m², between PATD and NICOM was 1.95 (−1.79-5.69) L/min/1.77 m², and between FATD and NICOM was 1.06 (−1.40-3.52) L/min/1.77 m². A moderate correlation was found between PATD and FATD (r = 0.43; P = 0.01), but no correlation was found between bioreactance and either PATD or FATD. Hypovolemia and volume expansion produced important significant differences in CI as measured by PATD and FATD, while the changes with bioreactance were small and non significant.

Conclusions

PATD and FATD measurements showed similar responses to hypovolemic shock and volume expansion. Bioreactance persistently underestimates the CI and is not significantly altered by either inducing hemorrhagic shock, or later, through volume expansion. Bioreactance is not a suitable method for monitoring the CI in pediatric hemorrhagic shock.     

肺源性心脏病呼吸衰竭病人行无创呼吸机治疗的护理

总结30例肺源性心脏病呼吸衰竭病人行无创呼吸机辅助治疗的护理,包括心理护理、上机前准备、使用中的生活护理、饮食护理、呼吸道管理、呼吸机的监测、病情观察、出现并发症后的护理等.     

无创机械通气治疗老年急性左心衰并呼吸衰竭的效果研究

目的探讨应用无创机械通气治疗老年急性左心衰并呼吸衰竭的效果。方法选取急性左心衰肺水肿并呼吸衰竭患者92例,采用随机数表法分为2组。对照组患者行常规治疗,观察组患者在常规治疗的基础上给予无创机械通气治疗。比较2组患者治疗后临床症状改善、动脉血气分压、RR、p H以及临床效果。结果治疗后,观察组患者临床症状改善情况、p(O_2)、p(CO_2)、RR、p H、总有效率显著优于对照组(P0.05)。结论对急性左心衰肺水肿并呼吸衰竭患者给予无创机械通气治疗,能够有效改善患者的心功能。     

Effect of bioimpedance body composition analysis on function of implanted cardiac devices

Background: It is routinely recommended that patients with pacemakers, implantable cardioverter defibrillators (ICD), and cardiac resynchronization therapy‐defibrillators (CRT‐D) avoid bioelectrical impedance analysis (BIA)—a commonly used method to estimate body composition—because of the concern for the potential for BIA interference with pacemaker or ICD function. However, the prevalence of such interference is not known. Objective: Assess for incidence of interference between BIA and ICD or CRT‐D devices. Methods and Results: Twenty patients with heart failure and cardiac implanted electronic devices (50% ICD, 50% CRT‐D) underwent BIA during real‐time device interrogation to detect interference. Study patients were 90% male, with mean age 54 ±14 years, and mean LVEF 23 ± 11%. Devices from all four leading cardiac device manufacturers were included. Device therapies were temporarily disabled to prevent inappropriate shocks. During body composition testing using BIA, no evidence of interference with ICD function was seen in any patient, including no telemetry disruption, no oversensing on any lead, and no patient symptoms. Conclusions: Despite the manufacturers’ recommendation to avoid BIA in patients with ICDs, this study showed no evidence of any interference in 20 patients. Bioimpedance analysis might be safe in such patients, but further confirmatory studies are required. (PACE 2012; 35:681–684)     

Antiarrhythmic effect of reverse electrical remodeling associated with cardiac resynchronization therapy

Background: Antiarrhythmic and proarrhythmic effects of cardiac resynchronization therapy (CRT) remain controversial. We hypothesized that reverse electrical remodeling (RER) with CRT is associated with reduced frequency of ventricular tachyarrhythmias (VTs). Methods: The width of native and paced QRS was measured in lead II electrocardiogram before and 13 ± 7 months after implantation of a CRT defibrillator device in 69 patients (mean age 66.3 ± 13.9; 39 males [83%]) with bundle branch block (BBB) (41 patients with left BBB and three patients with bifascicular block) or nonspecific intraventricular conduction delay (25 patients, 36%), and New York Heart Association class III–IV heart failure. Biventricular pacing was inhibited for 10 seconds to record native QRS. RER was defined as a decrease in the native QRS duration ≥10 ms compared to preimplant. Patients were followed prospectively 24 ± 13 months after assessment for electrical remodeling. Results: RER was observed in 22 patients (32%), among whom QRS duration decreased by 30.9 ± 14.1 ms (P < 0.00001) with similar heart rate and QRS morphology. Native QRS duration increased by 10.3 ± 16.6 ms in the other 47 patients (68%) (P = 0.0001). Baseline mean ejection fraction did not differ between patients with and those without RER (24.9 ± 10.0 vs 24.2 ± 8.6%, NS). During 2 ± 1 years of further follow‐up, 19 patients had VTs and 12 patients died. RER was associated with a fourfold decrease in the risk of death or sustained VTs requiring appropriate implantable cardioverter‐defibrillator therapies, whichever came first (hazard ratio 0.25; 95% confidence interval 0.08–0.85; P = 0.026). Conclusion: RER of the native conduction with CRT is associated with decreased mortality and antiarrhythmic effect of CRT. (PACE 2011; 34:357–364)     

Atrial fibrillation is associated with decreased cardiac sympathetic response to isometric exercise in CHF in comparison to sinus rhythm

Background: The presence of atrial fibrillation (AF) in congestive heart failure (CHF) is accompanied by increased mortality, although the exact mechanism is unclear. In previous studies, we have demonstrated cardiac baroreceptor abnormalities in association with AF and CHF. In this study, we sought to examine the effect of cardiac rhythm on the cardiac sympathetic response to exercise in CHF.
Methods: In 13 CHF patients (six AF, seven SR, left ventricular ejection fraction 31 ± 2%, age 61 ± 1 years), we measured the hemodynamic and cardiac sympathetic response isometric handgrip (IHG) exercise.
Results: At baseline the groups were well matched. Baseline hemodynamics and cardiac sympathetic activity did not significantly differ between the cohorts. In response to IHG exercise, both groups demonstrated significant hemodynamic responses. In conjunction, the sinus rhythm (SR) group demonstrated a significant increase in cardiac sympathetic response to exercise (P = 0.04) while in contrast the AF group did not (P = 0.6).
Conclusion: In this study, we demonstrate for the first time that the combination of AF and CHF is accompanied by a marked attenuation of the cardiac sympathetic response to acute hemodynamic stress. This implies AF is associated with a further impairment of baroreceptor response in CHF compared to SR. These findings present possible insights to the associated increased mortality and pathogenesis of AF with CHF.     

Reproducibility of thermodilution cardiac output determination in critically ill patients: Comparison between bolus and continuous method

Objective. A semi-continuous thermodilution method (CCO) was recently developed to measure cardiac output with less risk of bacterial contamination, fluid overload, and user-induced errors than the classical bolus technique (BCO). Previous comparison between these two methods showed negligible bias. However, large limits of agreement suggest that the two methods are not interchangeable. We hypothesized that this poor agreement may be due to differences in reproducibility.Methods. In 23 critically ill patients, 369 paired measurements of CCO and BCO were compared (range of cardiac outputs: 2.8 to 16 L/min). The reproducibility of BCO and CCO methods was evaluated on a sample of 205 and 209 determinations, respectively.Results. The comparison between the CCO and the BCO methods confirmed previous results: i.e., small bias (–0.39 L/min) and large limits of agreement -2.06 to +1.28 L/min). Reproducibility showed no bias for either the CCO or the BCO method. Limits of reproducibility agreement between repeated determinations were approximately 50% less for CCO than for BCO method: respectively –0.87 to +0.82 L/min for the CCO method and –1.56 to +1.37 L/min for the BCO method. Consequently, the threshold necessary to ascertain that the difference between two measurements was not due to the internal variability of the method (3 x SEM) was 0.39 for the CCO method and 0.75 L/min for the BCO method.Conclusion. Differences in reproducibility may explain the poor agreement between the CCO and BCO methods. The better reproducibility of the CCO method allows the detection of smaller variations in cardiac output and suggests the superiority of this new method.     

Accuracy of continuous thermodilution cardiac output monitoring by pulmonary artery catheter during therapeutic hypothermia in post-cardiac arrest patients

Purpose

Thermodilution continuous cardiac output measurements (TDCCO) by pulmonary artery catheter (PAC) have not been validated during therapeutic hypothermia in post-cardiac arrest patients. The calculated cardiac output based on the indirect Fick principle (FCO) using pulmonary artery blood gas mixed venous oxygen saturation (FCO-BG-SvO2) is considered as the gold standard. Continuous SvO2 by PAC (PAC-SvO2) has also not been validated previously during hypothermia. The aims of this study were (1) to compare FCO-BG-SvO2 with TDCCO, (2) to compare PAC-SvO2 with BG-SvO2 and finally (3) to compare FCO with SvO2 obtained via PAC or blood gas.

Methods

We analyzed 102 paired TDCCO/FCO-BG-SvO2 and 88 paired BG-SvO2/PAC-SvO2 measurements in 32 post-cardiac arrest patients during therapeutic hypothermia.

Results

TDCCO was significantly although poorly correlated with FCO-BG-SvO2 (R² 0.21, p < 0.01) without systematic bias (−0.15 ± 1.76 l/min). Analysis according to Bland and Altman however showed broad limits of agreement ([−3.61; 3.45] l/min) and an unacceptable high percentage error (105%). None of the criteria for clinical interchangeability were met. Concordance analysis showed that TDCCO had limited trending ability (R² 0.03). FCO based on PAC-SvO2 was highly correlated with FCO-BG-SvO2 (R² 0.72) with a small bias (−0.08 ± 0.72 l/min) and slightly too high percentage error (44%).

Conclusion

Our results show an extreme inaccuracy of TDCCO by PAC in post-cardiac arrest patients during therapeutic hypothermia. We found a reasonable correlation between BG-SvO2 and PAC-SvO2 and subsequently between FCO calculated with SvO2 obtained either via blood gas or PAC. The decision to start or titrate inotropics should therefore not be guided by TDCCO in this setting.     

Time course of effects of cardiac resynchronization therapy in chronic heart failure: benefits in patients with preserved exercise capacity

Objectives: To assess in patients with chronic heart failure the effect of cardiac resynchronization therapy (CRT) over 12 months' follow-up the time course of the changes in functional and neurohormonal indices and to identify responders to CRT.
Methods: Eighty-nine patients (74.1 ± 1 years, left ventricular ejection fraction [LVEF] < 35%), QRS complex duration >150 ms, in stable New York Heart Association (NYHA) class III or IV on optimal medical treatment were prospectively randomized either in a control (n = 45) or CRT (n = 44) group and underwent clinical evaluation, cardiopulmonary exercise testing (CPET), 2D-Echo, heart rate variability (HRV), carotid baroreflex (BRS), and BNP assessments before and at 6- and 12-month follow-up.
Results: In the CRT group, improvement of cardiac indices and BNP concentration were evident at medium term (over 6 months) follow-up, and these changes persisted on a longer term (12 months) (all P < 0.05). Instead CPET indices and NYHA class improved after 12 months associated with restoration of HRV and BRS (all P < 0.05). We identified 26 responders to CRT according to changes in LVEF and diameters. Responders presented less depressed hemodynamic (LVEF 25 ± 1.0 vs 22 ± 0.1%), functional (peak VO₂ 10.2 ± 0.2 vs 6.9 ± 0.3 ml/kg/min), and neurohormonal indices (HRV 203.6 ± 15.7 vs 147.6 ± 10.ms, BRS 4.9 ± 0.2 vs 3.6 ± 0.3 ms/mmHg) (all P < 0.05). In the multivariate analysis, peak VO₂ was the strongest predictor of responders.
Conclusions: Improvement in functional status is associated with restoration of neurohormonal reflex control at medium term. Less depressed functional status (peak VO₂) was the strongest predictor of responders to CRT.     

Cardiac output measurement in children: comparison of the Ultrasound Cardiac Output Monitor with thermodilution cardiac output measurement

OBJECTIVE: To compare the assessment of cardiac output (CO) in children using the noninvasive Ultrasound Cardiac Output Monitor (USCOM) with the invasive pulmonary artery catheter (PAC) thermodilution cardiac output measurement. DESIGN AND SETTING: Prospective observational study in a tertiary center for pediatric cardiology of a university children's hospital. PATIENTS: Twenty-four pediatric patients with congenital heart disease without shunt undergoing cardiac catheterization under general anesthesia. MEASUREMENTS AND RESULTS: CO was measured by USCOM using a suprasternal CO Doppler probe in children undergoing cardiac catheterization. USCOM data were compared to CO simultaneously measured by PAC thermodilution technique. Measurements were repeated three times within 5 min in each patient. A mean percentage error not exceeding 30% was defined as indicating clinical useful reliability of the USCOM. CO values measured by PAC ranged from 1.3 to 5.3 l/min (median 3.6 l/min). Bias and precision were -0.13 and 1.34 l/min, respectively. The mean percentage error of CO measurement by the USCOM compared to PAC thermodilution technique was 36.4% for USCOM. CONCLUSIONS: Our preliminary data demonstrate that cardiac output measurement in children using the USCOM does not reliably represent absolute CO values as compared to PAC thermodilution. Further studies must evaluate the impact of incorporating effective aortic valve diameters on CO measurement using the USCOM.