Rishi Tappeta
Research Mentor(s): Joseph Potkay
Department or Program: Michigan Medicine Department of Surgery
Authors: Rishi Tappeta*, Megha Jacob*, Andrew Zhang, Martin Daman, Wyeth Alexander, Alvaro Rojas-Peña, Joseph A Potkay
Session: Session 1: 12:00pm-12:50pm
Poster: 6
Abstract
Study:
Current Extracorporeal Membrane Oxygenation (ECMO) systems rely on hospital staff to make adjustments to the sweep gas of the artificial lung (AL) to control patient arterial CO2 (PaCO2) levels. However, these changes require periodic blood samples. This leaves the opportunity for changes in PaCO2 levels in between blood samples, particularly when the patient is ambulatory or undergoing physical therapy. An ECMO system that automatically and rapidly adjusts the sweep gas to precisely control patient PaCO2 would reduce staffing effort, increase patient comfort, and improve patient activity and rehabilitation. This work reports an ECMO sweep gas controller that regulates sweep gas based on the CO2 levels in the gas coming out of the AL.
Methods:
An integrated system was developed that automatically modulates gas flow rate through any commercially available AL in response to changing metabolic rates and blood CO2 levels. The CO2 concentration in the AL exhaust gas (EGCO2) is sampled (SparkFun SPX-18385) as an analog for blood pCO2 measurements. The system adjusts the sweep gas through the AL in real-time through gas flow controllers (Cole Parmer 32907-73) to achieve a target EGCO2 (tEGCO2) value using a proportional integral derivative (PID) controller.
A long term test with water was set up and run over the course of 5 days. The circuit consisted of a water heater, centrifugal pump, sweep gas controller system, and an AL. Following the long term water test, in vivo tests were performed on two adult sheep (~100kg). The first test performed was fixed EGCO2 while the second sheep was fixed sweep.
Results:
The integrated controller responded to metabolic changes to maintain a specified EGCO2 when the negative feedback system was in effect.
Conclusions:
This ECMO system uses a negative feedback algorithm to automatically respond to changes in patient metabolism, reducing the fluctuation of blood pCO2 compared to the current standard of fixed sweep gas. This can be used to reduce the monitoring requirements for patients (blood sampling), and better maintain patient comfort during periods of rest or physical exertion.
