Abstract PR051: Evaluation of A Capnodynamic Method for Monitoring Effective Pulmonary Blood Flow in An Ischemia and Reperfusion Porcine Model

Background & Objectives: A capnodynamic equation can be used to calculate effective pulmonary blood flow (COEPBF) i.e. cardiac output (CO) minus shunt.(1) An ischemic injury with subsequent reperfusion increases the concentrations of carbon dioxide temporarily, a situation that theoretically could affect the agreement of a capnodynamic method. The aim of the current study was to evaluate COEPBF during rapid changes in PvCO2 in an ischemia and reperfusion porcine model. Materials & Methods: The required alterations of alveolar concentration of carbon dioxide are created by a ventilatory pattern containing cyclic reoccurring expiratory holds. The mathematical model used to calculate COEPBF assumes a steady state in PvCO2 levels. COEPBF was compared to a reference method for CO, an ultrasonic flow probe around the pulmonary trunk and a pulmonary artery catheter in a porcine model (N=8). A 10 Fr Reliant catheter (Medtronic) was placed in the aorta below the diaphragm via the femoral artery and inflated until blood flow in the contralateral femoral artery was abolished according to ultrasound doppler. Hemodynamic measurements, lactate levels and PvCO2 were obtained at baseline before balloon inflation, at minute 27 of ischemia and after deflation at minute one, three and five during reperfusion. Results: The ischemic model resulted in significant changes in lactate and PvCO2 levels from baseline 1.5 mmol/L (1.2–2.4) and 8,5 kPa (7.2–11.4) at baseline to 8.2 mmol/L (7.2–9.0) and 5.2 kPa (4.1–6.2) at minute 27 of ischemia and 10.4 mmol/L (7.8–11.4) and 10.7 kPa (9.0–12.3) at minute one after deflation. At baseline a Bland Altman plot showed bias 0.6 L/min, limits of agreement (LoA) -0.2 – 1.6 L/min and a percentage error (PE) 22%. At minute five bias was 0.02 L/min, LoA -1.8 – 1.8 L/min and PE 36%.Conclusion: COEPBF recuperates fast after rapid changes in PvCO2 resuming acceptable levels of agreement in 5 minutes. References: 1. Hallsjo Sander C et al. Novel continuous capnodynamic method for cardiac output assessment during mechanical ventilation. British journal of anaesthesia. 2014;112(5):824–31. Disclosure of Interest: T. Sigmundsson: None declared, T. Öhman: None declared, C. Hällsjö-Sander: None declared, M. Hallbäck: None declared, F. Suarez Sipman Conflict with: Performs colsulting activities for Maquet Critical Care, M. Wallin Employee of: At Maquet Critical Care, H. Björne Research grant/funding from: Maquet Critical Care and regional agreement on medical training (ALF) between Stockholm County Council and Karolinska Institute