  This paper proposes a novel, simple and minimally invasive method for stroke
volume variation assessment using arterial blood pressure measurements. The
arterial blood pressure signal is reconstructed using a semi-classical signal
analysis method allowing the computation of a parameter, called the first
systolic invariant INVS1. We show that INVS1 is linearly related to stroke
volume. To validate this approach, a statistical comparaison between INVS1 and
stroke volume measured with the PiCCO technique was performed during a 15-mn
recording in 21 mechanically ventilated patients in intensive care. In 94% of
the whole recordings, a strong correlation was estimated by cross-correlation
analysis (mean coefficient=0.9) and linear regression (mean coefficient=0.89).
Once the linear relation had been verified, a Bland-Altman test showed the very
good agreement between the two approaches and their interchangeability. For the
remaining 6%, INVS1 and the PiCCO stroke volume were not correlated at all, and
this discrepancy, interpreted with the help of mean pressure, heart rate and
peripheral vascular resistances, was in favor of INVS1.
