A comparison of cardiac output derived from the arterial pressure wave against thermodilution in cardiac surgery patients

In three clinical centres, we compared a new method for measuring cardiac output with conventional thermodilution. The new method computes beat-to-beat cardiac output from radial artery pressure by simulating a three-element model of aortic input impedance, and includes non-linear aortic mechanical properties and a self-adapting systemic...

The compliance of the porcine pulmonary artery depends on pressure and heart rate

1. The influence of mean pulmonary arterial pressure (mean P(pa)) on dynamic (C(d)) and pseudostatic compliance (C(ps)) of the pulmonary artery was studied at a constant and a changing heart rate. C(d) is the change in cross-sectional area (CSA) relative to the change in P(pa) throughout a heart cycle. C(pa) is the change in mean CSA relative to...

Single injection thermodilution: A flow-corrected method

Application of the Stewart-Hamilton equation in the thermodilution technique requires flow to be constant. In patients in whom ventilation of the lungs is controlled, flow modulations may occur leading to large errors in the estimation of mean cardiac output. Methods: To eliminate these errors, a modified equation was developed. The resulting...

Computation of aortic flow from pressure in humans using a nonlinear, three-element model

We computed aortic flow pulsations from arterial pressure by simulating a nonlinear, time-varying three-element model of aortic input impedance. The model elements represent aortic characteristic impedance, arterial compliance, and systemic vascular resistance. Parameter values for the first two elements were computed from a published, age...

An adequate strategy for the thermodilution technique in patients during mechanical ventilation

The application of the thermodilution method in conditions associated with variations in blood flow implies a misuse of the Stewart Hamilton equation. Therefore, we studied the reliability of the thermodilution method for the estimation of mean cardiac output (CO) during mechanical ventilation in patients (n = 9). Variation of the injection...

Continuous cardiac output monitoring by pulse contour during cardiac surgery

Most pulse contour methods are unreliable under changing haemodynamic conditions, because no corrections are made for pressure-dependent compliance and reflections of pressure waves. The pulse contour method of Wesseling includes such corrections. Four thermodilution measurements equally spread over the ventilatory cycle were used to calibrate...