Stroke volume from central aortic pressure? A critical assessment of the various formulae as to their clinical value.

Pulsecontour methods remain a potentially attractive approach for the calculation of stroke volume, since they might provide such information on a beat to beat basis, after a single calibration. In order to test the clinical value of this hypothesis stroke volume estimates from six different pulsecontour formulae were compared with stroke volume values obtained with an electromagnetic flowmeter in 10 pigs. Each of the formulae failed to confirm its usefulness under circumstances mimicking clinical conditions. The calibration constant obtained during control states varied widely (+/- 25%). In many instances polsecontour formulae predicted changes in stroke volume in a direction opposite from those measured. The need for recalibration was so frequent that the calibration merthod itself proved often sufficiently informative. It is concluded that in intensive care units pulsecontour formulae cannot contribute to the care of the patient. Its popularity is not justified and its increased use since the introduction of computers is not warranted.