Pulse Pressure Analysis

Semi-invasive measurement of cardiac output based on pulse contour: a review and analysis

PURPOSE

The aim of this review was to provide a meta-analysis of all five of the most popular systems for arterial pulse contour analysis compared with pulmonary artery thermodilution, the established reference method for measuring cardiac output (CO). The five investigated systems are FloTrac/Vigileo(®), PiCCO(®), LiDCO/PulseCO(®), PRAM/MostCare(®), and Modelflow.

SOURCE

In a comprehensive literature search through MEDLINE(®), Web of Knowledge (v.5.11), and Google Scholar, we identified prospective studies and reviews that compared the pulse contour approach with the reference method (n = 316). Data extracted from the 93 selected studies included range and mean cardiac output, bias, percentage error, software versions, and study population. We performed a pooled weighted analysis of their precision in determining CO in various patient groups and clinical settings.

PRINCIPAL FINDINGS

Results of the majority of studies indicate that the five investigated systems show acceptable accuracy during hemodynamically stable conditions. Forty-three studies provided adequate data for a pooled weighted analysis and resulted in a mean (SD) total pooled bias of -0.28 (1.25) L·min(-1), percentage error of 40%, and a correlation coefficient of r = 0.71. In hemodynamically unstable patients (n = 8), we found a higher percentage error (45%) and bias of -0.54 (1.64) L·min(-1).

CONCLUSION

During hemodynamic instability, CO measurement based on continuous arterial pulse contour analysis shows only limited agreement with intermittent bolus thermodilution. The calibrated systems seem to deliver more accurate measurements than the auto-calibrated or the non-calibrated systems. For reliable use of these semi-invasive systems, especially for critical therapeutic decisions during hemodynamic disorders, both a strategy for hemodynamic optimization and further technological improvements are necessary.

[Minimally invasive cardiopulmonary monitoring with the PiCCO Plus system]

Insertion of a central venous catheter and an arterial catheter would be indicated in hemodynamically unstable or severely hypoxic patients in critical care units. In this setting, cardiorespiratory monitoring by transpulmonary thermodilution (TPTD) can be considered minimally invasive given that only a single arterial thermodilution catheter and a single central venous catheter are required to be connected to a specific monitor (the PiCCO Plus, Pulsion Medical Systems, Munich, Germany). TDTP simultaneously measures cardiac output, preloading, and cardiac function in hemodynamically unstable patients and predicts the response to volume. The technique can be managed by any health care professional. In hypoxic patients, TDTP identifies cases of pulmonary edema that might benefit from a negative fluid balance, evaluates pulmonary vascular permeability, facilitates our understanding of pathophysiologic mechanisms of hypoxemia, and predicts the likelihood of deleterious hemodynamic effects of positive end-expiratory pressures.

Evaluation of a new arterial pressure-based cardiac output device requiring no external calibration

BACKGROUND

Several techniques have been discussed as alternatives to the intermittent bolus thermodilution cardiac output (COPAC) measurement by the pulmonary artery catheter (PAC). However, these techniques usually require a central venous line, an additional catheter, or a special calibration procedure. A new arterial pressure-based cardiac output (COAP) device (FloTractrade mark, Vigileotrade mark; Edwards Lifesciences, Irvine, CA, USA) only requires access to the radial or femoral artery using a standard arterial catheter and does not need an external calibration. We validated this technique in critically ill patients in the intensive care unit (ICU) using COPAC as the method of reference.

METHODS

We studied 20 critically ill patients, aged 16 to 74 years (mean, 55.5 +/- 18.8 years), who required both arterial and pulmonary artery pressure monitoring. COPAC measurements were performed at least every 4 hours and calculated as the average of 3 measurements, while COAP values were taken immediately at the end of bolus determinations. Accuracy of measurements was assessed by calculating the bias and limits of agreement using the method described by Bland and Altman.

RESULTS

A total of 164 coupled measurements were obtained. Absolute values of COPAC ranged from 2.80 to 10.80 l/min (mean 5.93 +/- 1.55 l/min). The bias and limits of agreement between COPAC and COAP for unequal numbers of replicates was 0.02 +/- 2.92 l/min. The percentage error between COPAC and COAP was 49.3%. The bias between percentage changes in COPAC (DeltaCOPAC) and percentage changes in COAP (DeltaCOAP) for consecutive measurements was -0.70% +/- 32.28%. COPAC and COAP showed a Pearson correlation coefficient of 0.58 (p < 0.01), while the correlation coefficient between DeltaCOPAC and DeltaCOAP was 0.46 (p < 0.01).

CONCLUSION

Although the COAP algorithm shows a minimal bias with COPAC over a wide range of values in an inhomogeneous group of critically ill patients, the scattering of the data remains relative wide. Therefore, the used algorithm (V 1.03) failed to demonstrate an acceptable accuracy in comparison to the clinical standard of cardiac output determination.