Non-Invasive Monitoring of Left Ventricular Contractility and Ventilatory Mechanics

The maximum left ventricular elastance (E_lv ^max ) is a valuable index of ventricular contractility. However, conventional methods for its measurements are too invasive for routine use. We propose a non-invasive technique for tracking changes in E_lv ^max by mathematically determining the dynamic coupling between beat-to-beat fluctuations in instantaneous lung volume and arterial blood pressure measured during random-interval breathing. The mathematical technique also provides an estimate of the dominant time constant of the ventilatory system (tau), which is equal to the product of the airway resistance and lung compliance. We then describe a theoretical evaluation of the technique with respect to realistic beat-to-beat variability generated by a cardiovascular simulator. Our results show that the technique is able to detect actual changes in the E_lv ^max and tau values of the simulator. With successful experimental testing, the technique may ultimately be employed to help guide therapy in heart failure patients