A Parameter Identification Approach towards Analyzing Hemodynamics Based on Capnography
Wolfgang J. Kern, Simon Orlob, Gabriel Putzer, Judith Martini, Martin Höller · Computing in cardiology · 2023
During cardiopulmonary resuscitation (CPR), end-tidal CO 2 (etCO 2 ) is often used as a surrogate parameter for systemic blood flow and a sudden rise in etCO 2 is regularly associated with a return of spontaneous circulation (ROSC).We model this transportation of metabolic CO 2 from the tissues via systemic perfusion to the lungs, and its exhalation through the alveoli, in a simple compartmentbased ODE model.The aim is to determine a slowly timedependent scalar describing the level of systemic perfusion based on tidal flow, airway pressure and capnography data in a multishooting parameter identification approach.We test our model on synthetically generated data as well as on data from a porcine model of cardiac arrest.In the porcine model, we compare the estimated level of systemic perfusion with invasively measured mean arterial blood pressure as a surrogate of blood flow.First experiments on both synthetic and real-world data show good identifiability for the level of systemic perfusion based on the capnography data.A validated simple ODE model for CO 2 -extraction during CPR could help to quantify the effects of tidal volumes and ventilation rates on etCO 2 and furthermore assist physicians to detect a ROSC more reliably during outof-hospital cardiac arrest.