***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective —To compare cardiac output measured by the transoesophageal Doppler and thermodilution techniques . Design — Prospect i ve direct comparison of paired measurements by both techniques in each patient . Setting —Intensive care unit in a cardiovascular centre . Patients —65 patients after open heart surgery ( mean ( SD ) age 53 ( 12 ) years ) . Interventions —Cardiac output was measured simultaneously by the transoesophageal Doppler and thermodilution techniques . Cardiac output was measured again after a mechanical intervention or volume loading . Results —The limits of agreement were −2·53 to + 0·83 1·min−1 for cardiac output measured by the Doppler and thermodilution techniques . This suggests that the Doppler method alone would not be suitable for clinical use . The second measurement of cardiac output by thermodilution was compared with cardiac output estimated from the first and second Doppler measurements and the first thermodilution measurement . The limits of agreement ( −0·55 to + 0·51 1·min−1 ) were good enough for clinical use . Conclusions —After cardiac output had been measured simultaneously by both the Doppler and thermodilution techniques , subsequent transoesophageal Doppler alone gave a clinical ly useful measurement of cardiac output OBJECTIVE To compare the haemodynamic measurements of cardiac output ( CO ) , central venous pressure ( CVP ) , pulmonary capillary wedge pressure ( Pw ) and pulmonary artery systolic pressure ( PASP ) , obtained by Swan-Ganz catheter and transthoracic echocardiography . MATERIAL AND METHODS Prospect i ve study in a Medical/Surgical Intensive Care Unit ( ICU ) . A total of 41 post liver transplant patients were enrolled .  CO , CVP , Pw and PASP , were simultaneously determined by two independent observers , utilizing a Swan-Ganz catheter and transthoracic echocardiography , using equations described in the literature . A linear correlation and a Bl and -Altman analysis were performed . RESULTS A good correlation between invasive and non- invasive measurements for CO ( r=0.97 ) and CVP ( r=0.88 ) was found , but determinations of Pw ( r=0.41 ) and PASP ( r=0.18 ) did not correlate well . Bias and 95 % confidence interval for CO were negligible namely when a CO<6 l/min was considered . Pulsed-wave Doppler-echocardiography underestimates the CO when compared with thermodilution , but the 2 techniques agree on average and can be used interchangeably . CONCLUSIONS The non-invasive determination of CO in critical care post liver transplant patients correlates well with the invasive determinations . Transthoracic echocardiography was not appropriate for calculating filling parameters studied . Although the data was obtained in post liver transplant patients , they could be useful in defining the role of echocardiography in the ICU Background and objective : Intraoperative Doppler ultrasound can be used to measure cardiac output by transoesophageal echocardiography . Recently , its reliability , when compared to the thermodilution technique , has been question ed . The purpose of this study was to compare intraoperative changes in cardiac output measured by echo‐Doppler and by thermodilution in cardiac surgery . We also assessed the agreement between the techniques . Methods : Fifty cardiac surgical patients ( 38 male , 12 female , mean age of 63.4 ± 14.3 yr ) were prospect ively included after approval by the Ethics Committee of the Institution . Cardiac output was assessed by thermodilution , with 10 mL saline at 12 ° C , and simultaneously and blindly by echo‐Doppler in deep transgastric view with pulsed wave Doppler at the level of the left ventricular outflow tract . Matched thermodilution cardiac output and echo‐Doppler cardiac output measurements were taken three times at the end of expiration , both pre‐ and post‐cardiopulmonary bypass . Results : Echo‐Doppler measurements were obtained in 44 patients ( 88 % ) . In three patients , Doppler recordings could not be obtained adequately , and three developed left ventricular outflow tract obstruction after bypass . Bl and ‐Altman analysis revealed a bias of 0.015 L min−1 , with narrow limits of agreement ( −1.21 to 1.22 L min−1 ) and 29.1 % error . Echo‐Doppler was accurate ( 92 % sensitivity and 71 % specificity , P = 0.008 by receiver operating characteristic curves ) for detecting more than 10 % of change in thermodilution cardiac output . There were no complications related to the study . Conclusions : The agreement between cardiac output by echo‐Doppler and by thermodilution is clinical ly acceptable and transoesophageal echocardiography is a reliable tool to assess significant cardiac output changes in a population of selected patients OBJECTIVE To compare cardiac output ( CO ) , stroke volume ( SV ) , and cardiac index ( CI ) as estimated with a new , noninvasive Doppler device ( Ultrasonic Cardiac Output Monitor [ USCOM ] ; USCOM Ltd , Sydney , Australia ) with those measured with the bolus thermodilution ( TD ) technique . DESIGN Prospect i ve nonr and omized study . SETTING Postcardiac surgery recovery unit of a tertiary cardiac center . PARTICIPANTS Fifty patients after off-pump coronary artery bypass ( OPCAB ) surgery . MEASUREMENT AND MAIN RESULTS Both right-sided and left-sided CO were estimated with a USCOM continuous-wave ( CW ) Doppler device , and CO was determined with the bolus TD technique performed in triplicate . On comparing the right-sided CO , SV , and CI with those of TD , the mean bias was 0.03 L/min , 1.6 mL , and 0.02 L/min/m(2 ) , respectively . The comparison of left-sided CO , SV , and CI with those of TD revealed a means bias of 0.14 L/min , 1.0 mL , and 0.08 L/min/m(2 ) , respectively . CONCLUSION This study showed excellent agreement between the values for CO , SV , and CI as determined with USCOM and TD . Since there was only 1 time period for CO estimation in each patient with both methods , the stability of this correlation needs to be further investigated over time Background : The use of transesophageal echocardiography for the determination of cardiac output ( CO ) has been limited to date . We assessed the capability of aortic continuous-wave Doppler transesophageal echocardiography to determine CO ( DCO ) in a transgastric long-axis imaging plane of the heart by comparing DCO to thermodilution CO ( TCO ) . Methods : DCO was determined in 63 consecutive patients undergoing cardiac surgery .  Aortic valve area was obtained from the transverse short-axis view of the valve assuming a triangular shape for the valve orifice . Stroke volume was calculated as the product of velocity – time integral and aortic valve area : stroke volume = velocity – time integral × aortic valve area . DCO was calculated off-line , by multiplying stroke volume with heart rate : DCO = stroke volume × heart rate . Results : The aortic valve orifice was easily imaged in all patients . Excellent- quality continuous-wave Doppler flow profiles were obtained in nearly all ( 62 of 63 ) . A total of 109 DCO determinations were performed . Mean DCO was 4.35 ± 1.18 1·min-1 ( range 2.02 - 7.42 1·min-1 ) , and mean TCO was 4.41 ± 1.17 1·min-1 ( range 2.24 - 8.94 1·min-1 ) . Very high correlation and agreement were found between the two methods : DCO = 0.94 × TCO + 0.19 , r=0.94 , SEE ( st and ard error of the estimate ) = 0.41 1·min-1 ; 95 % confidence interval=0.06 ± 0.83 1·min-1 . Relative changes from pre- to postbypass CO ( Δ ) also showed a strong correlation ( ΔDCO=0.93 × ΔTCO + 5.4 % , r=0.82 , SEE=17.8 % ) . For CO changes greater than 10 % , Doppler was in accordance with thermodilution in 43 of 45 measurements . DCO repeatability coefficient was 0.51 1·min-1 . Conclusions : Compared to thermodilution , continuous-wave Doppler measurements of blood flow velocity across the aortic valve in the transesophageal echocardiographic transgastric view allow accurate CO determination 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 Prospect i ve 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 BACKGROUND The USCOM ultrasonic cardiac output monitor ( USCOM Pty Ltd , Coffs Harbour , NSW , Australia ) is a non-invasive device that determines cardiac output by continuous-wave Doppler ultrasound . The aim of this study was to evaluate the accuracy of the USCOM device compared with the thermodilution technique in intensive care patients who had just undergone cardiac surgery . METHODS We conducted a prospect i ve study in the 18-bed intensive care unit of a 600-bed tertiary referral hospital . Twenty-four mechanically ventilated patients were studied immediately following cardiac surgery . We evaluated the USCOM monitor by comparing its output with paired measurements obtained by the st and ard thermodilution technique using a pulmonary artery catheter . RESULTS Forty paired measurements were obtained in 22 patients . We were unable to obtain an acceptable signal in the remaining two patients . Comparison of the two techniques showed a bias of 0.18 and limits of agreement of -1.43 to 1.78 . The agreement may not be as good between techniques at higher cardiac output values . CONCLUSIONS The USCOM monitor has a place in intensive care monitoring . It is accurate , rapid , safe , well-tolerated , non-invasive and cost-effective . The learning curve for skill acquisition is very short . However , during the learning phase the USCOM monitor measurements are rather ' operator dependent ' . Its suitability for use in high and low cardiac output states requires further validation The present study compares the cardiac output ( CO ) estimated by a new , non-invsive continuous Doppler device ( Ultrasonic cardiac output monitor-USCOM ) with that by bolus thermodilution technique ( TD ) .  Thirty post off-pump coronary artery bypass graft surgery patients were studied in this prospect i ve nonr and omized study . Right heart CO estimation by USCOM and TD was performed and measured in quadruplet . A total of 120 paired observations were made . The mean CO was 4.63 and 4.76 Llmin as estimated by TD and USCOM respectively . For TD and USCOM , the CO had a mean bias ( tendency of one technique to differ from other ) of -0.13 L/min and limits of agreement ( mean bias + /- 2SD ) at -0.86 and 0.59 L/min . The study reveals very good agreement between the values of CO estimated by USCOM and TD 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 aim ed at comparing the accuracy of the USCOM device with that of the thermodilution technique in patients with septicemia . We conducted a prospect i ve 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 ( n = 70 ) . 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 r = 0.89 . Comparison by Bl and -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 Sixteen obstetric patients 
    Output:
    
Although the difference in CO between echocardiography by different types or sites and TD was not entirely consistent , the overall effect of meta- analysis showed that no significant differences were observed between US and TD .
The techniques may be interchangeable under certain conditions