The physiology of venoarterial extracorporeal membrane oxygenation - A comprehensive clinical perspective

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has become a standard of care for severe cardiogenic shock, refractory cardiac arrest and related impending multiorgan failure. The widespread clinical use of this complex temporary circulatory support modality is still contrasted by a lack of formal scientific evidence in the current literature. This might at least in part be attributable to VA ECMO related complications, which may significantly impact on clinical outcome. In order to limit adverse effects of VA ECMO as much as possible an indepth understanding of the complex physiology during extracorporeally supported cardiogenic shock states is critically important. This review covers all relevant physiological aspects of VA ECMO interacting with the human body in detail. This, to provide a solid basis for health care professionals involved in the daily management of patients supported with VA ECMO and suffering from cardiogenic shock or cardiac arrest and impending multiorgan failure for the best possible care.</p

INFLUENCE OF PULSATILE CATHETER PUMP SYNCHRONIZATION ON HAEMODYNAMIC VARIABLES: NUMERICAL SIMULATION

Severe cardiovascular diseases can be treated using left ventricular assist devices (LVAD). One of the possible LVADs is the Pulsatile Catheter (PUCA) pump that consists of a hydraulically or pneumatically driven membrane pump connected to a valved catheter. In this work a numerical model of the cardiocirculatory system and of the PUCA have been developed in order to study their interaction. In the numerical simulator a pathological condition of the left ventricle has been reproduced and successively the effects of the PUCA on the haemodynamic variables applied were studied. Different functioning modes were tested by changing the ratio between the pump frequency and the heart beat rate (HR) as 1:1, 1:2 or 1:3 and by introducing a delay time between the cardiac and the PUCA cycle. The performance of the pump was evaluated in terms of cardiac output, PUCA and coronary flows and it was studied for different HR values. Results show a good resemblance between the model and literature data and indicate that different synchronization and timing can influence the functioning of the pump. In particular, the frequency ratio and the time delay of the pump cycle can contribute to optimize the performance of the PUCA

The Hypotension Prediction Index is equally effective in predicting intraoperative hypotension during non-cardiac surgery compared to a mean arterial pressure threshold: a prospective observational study

BackgroundThe Hypotension Prediction Index is designed to timely predict intraoperative hypotension and is based on arterial waveform analysis using machine learning. It has recently been suggested that this algorithm is highly correlated with the mean arterial pressure (MAP) itself. Therefore, the aim of this study was to compare the Index with MAP based prediction methods and it is hypothesized that their ability to predict hypotension is comparable.MethodsIn this observational study, the Hypotension Prediction Index was used in addition to routine intraoperative monitoring during moderate- to high-risk elective non-cardiac surgery. The agreement in time between the default Hypotension Prediction Index alarm (&gt;85) and different concurrent MAP thresholds was evaluated. Additionally, the predictive performance of the Index and different MAP based methods were assessed within five, ten and fifteen minutes before hypotension occurred.ResultsA total of 100 patients were included. A MAP threshold of 73 mmHg agreed 97% of the time with the default Index alarm, while a MAP threshold of 72 mmHg had the most comparable predictive performance. The areas under the receiver operating characteristic curve of the Hypotension Prediction Index (0.89 (0.88-0.89)) and concurrent MAP (0.88 (0.88-0.89)) were almost identical for predicting hypotension within five minutes, outperforming both linearly extrapolated MAP (0.85 (0.84-0.85)) and delta MAP (0.66 (0.65-0.67)). The positive predictive value was 31.9 (31.3–32.6)% for the default Index alarm and 32.9 (32.2–33.6)% for a MAP threshold of 72 mmHg.ConclusionIn clinical practice, the Hypotension Prediction Index alarms are highly similar to those derived from MAP, which implies that the machine learning algorithm could be substituted by an alarm based on a MAP threshold set at 72 or 73 mmHg. Further research on intraoperative hypotension prediction should therefore include comparison with MAP based alarms and related effects on patient outcome

INFLUENCE OF PULSATILE CATHETER PUMP SYNCHRONIZATION ON HAEMODYNAMIC VARIABLES: NUMERICAL SIMULATION

Severe cardiovascular diseases can be treated using left ventricular assist devices (LVAD). One of the possible LVADs is the Pulsatile Catheter (PUCA) pump that consists of a hydraulically or pneumatically driven membrane pump connected to a valved catheter. In this work a numerical model of the cardiocirculatory system and of the PUCA have been developed in order to study their interaction. In the numerical simulator a pathological condition of the left ventricle has been reproduced and successively the effects of the PUCA on the haemodynamic variables applied were studied. Different functioning modes were tested by changing the ratio between the pump frequency and the heart beat rate (HR) as 1:1, 1:2 or 1:3 and by introducing a delay time between the cardiac and the PUCA cycle. The performance of the pump was evaluated in terms of cardiac output, PUCA and coronary flows and it was studied for different HR values. Results show a good resemblance between the model and literature data and indicate that different synchronization and timing can influence the functioning of the pump. In particular, the frequency ratio and the time delay of the pump cycle can contribute to optimize the performance of the PUCA

The physiology of venoarterial extracorporeal membrane oxygenation - A comprehensive clinical perspective

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has become a standard of care for severe cardiogenic shock, refractory cardiac arrest and related impending multiorgan failure. The widespread clinical use of this complex temporary circulatory support modality is still contrasted by a lack of formal scientific evidence in the current literature. This might at least in part be attributable to VA ECMO related complications, which may significantly impact on clinical outcome. In order to limit adverse effects of VA ECMO as much as possible an indepth understanding of the complex physiology during extracorporeally supported cardiogenic shock states is critically important. This review covers all relevant physiological aspects of VA ECMO interacting with the human body in detail. This, to provide a solid basis for health care professionals involved in the daily management of patients supported with VA ECMO and suffering from cardiogenic shock or cardiac arrest and impending multiorgan failure for the best possible care.</p

Influence of Pulsatile Catheter Pump Synchronization on Haemodynamic Variables: Numerical Simulation.

Severe cardiovascular diseases can be treated using left ventricular assist devices (LVAD). One of the possible LVADs is the Pulsatile Catheter (PUCA) pump that consists of a hydraulically or pneumatically driven membrane pump connected to a valved catheter. In this work a numerical model of the cardiocirculatory system and of the PUCA have been developed in order to study their interaction. In the numerical simulator a pathological condition of the left ventricle has been reproduced and successively the effects of the PUCA on the haemodynamic variables applied were studied. Different functioning modes were tested by changing the ratio between the pump frequency and the heart beat rate (HR) as 1:1, 1:2 or 1:3 and by introducing a delay time between the cardiac and the PUCA cycle. The performance of the pump was evaluated in terms of cardiac output, PUCA and coronary flows and it was studied for different HR values. Results show a good resemblance between the model and literature data and indicate that different synchronization and timing can influence the functioning of the pump. In particular, the frequency ratio and the time delay of the pump cycle can contribute to optimize the performance of the PUCA

Simulators and Simulations for Extracorporeal Membrane Oxygenation: An ECMO Scoping Review

Classification; Extracorporeal life support; Simulation trainingClassificació; Suport vital extracorpòri; Formació en simulacióClasificación; Soporte vital extracorpóreo; Formación en simulaciónHigh-volume extracorporeal membrane oxygenation (ECMO) centers generally have better outcomes than (new) low-volume ECMO centers, most likely achieved by a suitable exposure to ECMO cases. To achieve a higher level of training, simulation-based training (SBT) offers an additional option for education and extended clinical skills. SBT could also help to improve the interdisciplinary team interactions. However, the level of ECMO simulators and/or simulations (ECMO sims) techniques may vary in purpose. We present a structured and objective classification of ECMO sims based on the broad experience of users and the developer for the available ECMO sims as low-, mid-, or high-fidelity. This classification is based on overall ECMO sim fidelity, established by taking the median of the definition-based fidelity, component fidelity, and customization fidelity as determined by expert opinion. According to this new classification, only low- and mid-fidelity ECMO sims are currently available. This comparison method may be used in the future for the description of new developments in ECMO sims, making it possible for ECMO sim designers, users, and researchers to compare accordingly, and ultimately improve ECMO patient outcomes.This research was funded by the 2022 “Boost Your Research” Fund in the Priority Program SPP 2014 “Towards an Implantable Lung” by the DFG, the German Research Foundation, grant number 20003297 UKA

Video based valve motion combined with Computational Fluid Dynamics gives stable and accurate simulations of blood flow in the Realheart® Total Artificial Heart

Background: Patients with end-stage, biventricular heart failure, and for whom heart transplantation is not an option, may be given a Total Artificial Heart (TAH). The Realheart® is a novel TAH which pumps blood by mimicking the native heart with translation of an atrioventricular plane. The aim of this work was to create a strategy for using Computational Fluid Dynamics (CFD) to simulate haemodynamics in the Realheart®, including motion of the atrioventricular plane and valves. Methods: The accuracies of four different computational methods for simulating fluid-structure interaction of the prosthetic valves were assessed by comparison of chamber pressures and flow rates with experimental measurements. The four strategies were: prescribed motion of valves opening and closing at the atrioventricular plane extrema; simulation of fluid-structure interaction of both valves; prescribed motion of the mitral valve with simulation of fluid-structure interaction of the aortic valve; motion of both valves prescribed from video analysis of experiments. Results: The most accurate strategy (error in ventricular pressure of 6%, error in flow rate of 5%) used video-prescribed motion. With the Realheart operating at 80 bpm, the power consumption was 1.03 W, maximum shear stress was 15 Pa, and washout of the ventricle chamber after 4 cycles was 87%.Conclusions: This study, the first CFD analysis of this novel TAH, demonstrates that good agreement between computational and experimental data can be achieved. This method will therefore enable future optimisation of the geometry and motion of the Realheart®