Realistic human muscle pressure for driving a mechanical lung

Abstract

Abstract Background: An important issue in noninvasivemechanical ventilation consists in understanding the origins of patient-ventilator asynchrony for reducing their incidence by adjusting ventilator settings to the intrinsic ventilatory dynamics of each patient. One of the possible ways for doing this is to evaluate the performances of the domiciliary mechanical ventilators using a test bench. Such a procedure requires to model the evolution of the pressure imposed by respiratory muscles, but for which there is no standard recommendations. Methods: In this paper we propose amathematicalmodel for simulating the muscular pressure developed by the inspiratorymuscles and corresponding to different patient ventilatory dynamics to drive the ASL 5000mechanical lung. Our model is based on the charge and discharge of a capacitor through a resistor, simulating contraction and relaxation phases of the inspiratory muscles. Results: Our resulting equations were used to produce 420 time series of the muscle pressure with various contraction velocities, amplitudes and shapes, in order to represent the inter-patient variability clinically observed. All these dynamics depend on two parameters, the ventilatory frequency and themouth occlusion pressure. Conclusion: Based on the equation of the respiratorymovement and its electrical analogy, the respiratory muscle pressure was simulated with more consistency in regards of physiological evidences than those provided by the ASL 5000 software. The great variability in the so-produced inspiratory efforts can covermost of realistic patho-physiological conditions. Keywords: