Monitoring left ventricular contractility from respiratory-induced blood pressure variability

The maximum lefi ventricular elastance ( E r ) is a valuable index of ventricular cantractitiry. However, traditional methods for its measurements are too invasive for practical use. We introduce a minimally invasive technique for monitoring E,; by mathematical analysis of beat-to-beatfluctuafions in arterial blood pressure and intrathoracic (esophageaI} pressure obtained during random-interval breathing. The technique exploits the concept that the magnitude of the bIood pressure drop immediately initiated by inspiration is due to E;I" and the nearly constant arterial compliance (CaJ. The technique estimates C,, E,r and may be utilized to monitor changes in E,"". We theoretically evaluated the technique by applying it to realistic beat-to-beat variability generated by a cardiovascular model. Our simulation results show rhat the technique is able to guontiJL CO Ely with little bias and can detect actual changes to the model E{Y.