***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 
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    ***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 In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old . Such investigations are often analysed inappropriately , notably by using correlation coefficients . The use of correlation is misleading . An alternative approach , based on graphical techniques and simple calculations , is described , together with the relation between this analysis and the assessment of repeatability Conventional Doppler methods for blood velocity estimation only estimate the velocity component along the ultrasound beam direction . This implies that a Doppler angle under examination close to 90deg results in unreliable information about the true blood direction and blood velocity . The novel method transverse oscillation ( TO ) , which combines estimates of the axial and the transverse velocity components in the scan plane , makes it possible to estimate the vector velocity of the blood regardless of the Doppler angle . The present study evaluates the TO method with magnetic resonance phase contrast angiography ( MRA ) by comparing in vivo measurements of stroke volume .  Eleven healthy volunteers were included in this prospect i ve study . From the obtained data sets recorded with the 2 modalities , vector velocity sequences were constructed and stroke volume calculated . Angle of insonation was approximately 90deg for TO measurements . The correlation between the stroke volume estimated by TO and MRA was 0.91 ( p<0.01 ) with the equation for the line of regression : MRA=1.1ldrTO-0.4 . A Bl and -Altman plot was additionally constructed where the mean difference was 0.2 ml with limits of agreement at -1.4 ml and 1.9 ml . The results indicate that reliable vector velocity estimates can be obtained in vivo using the presented angle-independent 2-D vector velocity method . The TO method can be a useful alternative to conventional Doppler systems by avoiding the angle artifact , thus giving quantitative velocity information 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 Purpose Goal -directed therapy in the perioperative setting has been shown to be associated with short-term improvements in outcome . This study assesses the longer-term survival of patients from a previous r and omized controlled trial of goal -directed therapy in high-risk surgical patients . Methods All patients from a previous r and omized controlled study were followed up for 15 years following r and omization to ascertain their length of survival following surgery . Factors that may be associated with increased survival were evaluated to determine what influenced long-term outcomes . Results Data from 106 of the original 107 patients ( 99 % ) were available for analysis . At 15 years , 11 ( 20.7 % ) of the goal -directed therapy patients versus 4 ( 7.5 % ) of the control group were alive ( p = 0.09 ) . Median survival for the goal -directed group was increased by 1,107 days ( 1,781 vs. 674 days , p = 0.005 ) . Long-term survival was associated with three independent factors : age [ hazard ratio ( HR ) 1.04 ( 1.02–1.07 ) , p < 0.0001 ] , r and omization to the goal -directed group of the study [ HR 0.61 ( 0.4–0.92 ) , p = 0.02 ] , and avoidance of a significant postoperative cardiac complication [ HR 3.78 ( 2.16–6.6 ) , p = 0.007 ] . Conclusions Long-term survival after major surgery is related to a number of factors , including patient age and avoidance of perioperative complications . Short-term goal -directed therapy in the perioperative period may improve long-term outcomes , in part due to its ability to reduce the number of perioperative complications PURPOSE The purpose of this study was to determine the dynamic changes in right ventricular ( RV ) and left ventricular ( LV ) output during positive airway pressure inspiratory hold maneuvers so as to characterize the interaction of processes in creating steady-state cardiac output during positive pressure ventilation . MATERIAL S AND METHODS We examined the disparity of RV and LV outputs at 5 seconds ( early ) and 20 seconds ( late ) into a 24-second inspiratory hold maneuver in 14 subjects in the intensive care unit immediately following coronary artery bypass surgery . RV output was measured by the thermodilution technique , whereas LV output was measured by the arterial pulse contour method .  RV and LV volumes were also measured by thermal and radionuclide ejection fraction techniques , respectively . RESULTS As P(aw ) was progressively increased from 0 to 20 cm H2O in sequential inspiratory hold maneuvers , both RV and LV outputs changed differently both at 5 seconds and 20 seconds into the inspiratory hold maneuvers . When expressed as change in cardiac output ( L/min ) for every cm H2O P(aw ) increase relative to end-expiratory values , RV output increased at 5 seconds ( 0.05 + /- 0.15 L/min ) then decreased at 20 seconds ( -0.08 + /- 0.21 , P < .05 ) . LV output decreased slightly at 5 seconds ( -0.14 + /- 0.22 ) and did not change from this minimal depressed level at 20 seconds ( P < .05 ) . Changes in RV and LV output were paralleled by changes in RV and LV end-diastolic volumes , respectively . CONCLUSION Positive pressure inspiration induces time-dependent changes in central hemodynamics , which are dissimilar between RV and LV function . Initially , inspiration increases RV output but decreases LV output , such that intrathoracic blood volume increases . However , sustained inspiratory pressures induce proportionally similar decreases in both RV and LV outputs . Thus , the hemodynamic effects of positive pressure ventilation will depend on the degree of lung inflation , the inspiratory time , and when measurements are made within the ventilatory cycle . These data also suggest that positive pressure ventilation with up to 20 cm H2 ) P(aw ) does not significantly impair ventricular performance in humans Introduction We wanted to determine the number of cold bolus injections that are necessary for achieving an acceptable level of precision for measuring cardiac index ( CI ) , indexed global end-diastolic volume ( GEDVi ) and indexed extravascular lung water ( EVLWi ) by transpulmonary thermodilution . Methods We included 91 hemodynamically stable patients ( age 59 ( 25 % to 75 % interquartile range : 39 to 79 ) years , simplified acute physiologic score (SAPS)II 59 ( 53 to 65 ) , 56 % under norepinephrine ) who were monitored by a PiCCO2 device . We performed five successive cold saline ( 15 mL , 6 ° C ) injections and recorded the measurements of CI , GED 
    Output:
    
Conclusions The majority of studies comparing echocardiography with thermodilution were difficult to interpret , but current evidence does not support interchangeability between these techniques in measuring cardiac output .