The Influence of Prone Positioning on the Accuracy of Calibrated and Uncalibrated Pulse Contour-Derived Cardiac Index Measurements
ABSTRACT BACKGROUND:Patients with lung failure who undergo prone positioning often receive extended hemodynamic monitoring. We investigated the influence of modified prone positioning (135°) on the accuracy of pulse contour-derived calibrated cardiac index (CIPC) and uncalibrated cardiac index (CIVIG) in this patient population with transpulmonary thermodilution (TPTD) as reference technique.METHODS:We studied 16 critically ill and mechanically ventilated patients (11 men, 5 women, aged 20-71 years) with acute lung injury or acute respiratory distress syndrome. Patients were monitored by TPTD with an integrated calibrated pulse contour technique (PiCCO®) and by uncalibrated pulse contour analysis (FloTrac/Vigileo™). Before prone positioning, cardiac index (given in L·min-1·m-2) was measured by TPTD (CITPTD) and CIPC was calibrated. After positioning, CIPC and CIVIG were read from the monitor and CITPTD was measured. After 8 to 10 hours, prone positioning was completed and measurements were performed analogously. Bland-Altman analysis based on a random-effects model was used to calculate limits of agreement (LOA) and percentage errors. Polar plots were used for trend analysis.RESULTS:Supine CITPTD was 3.3 ± 0.9 (mean ± SD) and CIVIG was 3.1 ± 0.8. After proning, CIPC was 3.5 ± 0.8, CIVIG 3.3 ± 0.8, and CITPTD 3.6 ± 0.8. Before repositioning, CITPTD was 3.5 ± 0.7 and CIVIG 3.3 ± 1.0. After repositioning, CITPTD was 3.1 ± 0.7, CIPC 3.3 ± 0.7, and CIVIG 2.9 ± 0.6. Mean bias pooled for proning and repositioning was -0.1 (LOA -0.7 to 0.6) for CIPC (percentage error 19%) and 0.3 (LOA -1.3 to 1.9) for CIVIG (percentage error 48%). Changes in CI were too small for trending analysis.CONCLUSION:Although calibrated CI measurements are only marginally influenced by prone positioning, according to the criteria of Critchley and Critchley, uncalibrated CI values show a degree of error, too high to be considered clinically acceptable.
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ABSTRACT: The FloTrac/Vigileo™, introduced in 2005, uses arterial pressure waveform analysis to calculate cardiac output (CO) and stroke volume variation (SVV) without external calibration. The aim of this systematic review is to evaluate the performance of the system. Sixty-five full manuscripts on validation of CO measurements in humans, published in English, were retrieved; these included 2234 patients and 44 592 observations. have been analysed according to underlying patient conditions, that is, general critical illness and surgery as normodynamic conditions, cardiac and (post)cardiac surgery as hypodynamic conditions, and liver surgery and sepsis as hyperdynamic conditions, and subsequently released software versions. Eight studies compared SVV with other dynamic indices. CO, bias, precision, %error, correlation, and concordance differed among underlying conditions, subsequent software versions, and their interactions, suggesting increasing accuracy and precision, particularly in hypo- and normodynamic conditions. The bias and the trending capacity remain dependent on (changes in) vascular tone with most recent software. The SVV only moderately agreed with other dynamic indices, although it was helpful in predicting fluid responsiveness in 85% of studies addressing this. Since its introduction, the performance of uncalibrated FloTrac/Vigileo™ has improved particularly in hypo- and normodynamic conditions. A %error at or below 30% with most recent software allows sufficiently accurate and precise CO measurements and trending for routine clinical use in normo- and hypodynamic conditions, in the absence of large changes in vascular tone. The SVV may usefully supplement these measurements.BJA British Journal of Anaesthesia 01/2014; DOI:10.1093/bja/aet429
- Journal of Cardiothoracic and Vascular Anesthesia 10/2014; 28(5). DOI:10.1053/j.jvca.2014.02.020
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ABSTRACT: OBJECTIVES: The aims of this study were to compare cardiac output (CO) measured by the new fourth-generation FloTracTM/VigileoTM system (Version 4.00) (COFVS) with that measured by a pulmonary artery catheter (COREF), and to investigate the ability of COFVS to track CO changes induced by increased peripheral resistance. DESIGN: Prospective study. SETTING: University Hospital. PARTICIPANTS: Twenty-three patients undergoing cardiac surgery. INTERVENTIONS: Phenylephrine (100 microg) was administered. MEASUREMENTS AND MAIN RESULTS: Hemodynamic variables, including COREF and COFVS, were measured before and after phenylephrine administration. Bland-Altman analysis was used to assess the discrepancy between COREF and COFVS. Four-quadrant plot and polar-plot analyses were utilized to evaluate the trending ability of COFVS against COREF after phenylephrine boluses. One hundred thirty-six hemodynamic interventions were performed. The bias shown by the Bland-Altman analysis was-0.66 L/min, and the percentage error was 55.4%. The bias was significantly correlated with the systemic vascular resistance index (SVRI) before phenylephrine administration (p<0.001, r2 = 0.420). The concordance rate determined by four-quadrant plot analysis and the angular concordance rate calculated using polar-plot analysis were 87.0% and 83.0%, respectively. Additionally, this trending ability was not affected by SVRI state. CONCLUSIONS: The trending ability of the new fourth-generation FloTracTM/VigileoTM system after increased vasomotor tone was greatly improved compared with previous versions; however, the discrepancy of the new system in CO measurement was not clinically acceptable, as in previous versions. For clinical application in critically ill patients, this vasomotor tone-dependent disagreement must be decreased.Journal of Cardiothoracic and Vascular Anesthesia 11/2014; 29(3). DOI:10.1053/j.jvca.2014.07.022