Nitric Oxide on Extracorporeal Life Support-Circuit Modifications for a Safe Therapy

Abstract

Nitric oxide (NO) incorporation into the sweep gas of the extracorporeal life support (ECLS) circuit has been proposed as a strategy to ameliorate the insults caused by the systemic inflammatory response. This technical study describes circuit modifications allowing nitric oxide to be incorporated into the circuit and describing and validating the oxygenator sweep flow rates necessary to achieve consistent safe delivery of the therapy. For patients requiring sweep rates less than 2 L/min, a simplified setup, incorporating a pressure relief valve/low flow meter in the gas delivery line, was placed in line between the blender/NO injector module and the NO sampling port/oxygenator. This setup allows titration of sweep to low flows without the need to blend in CO2 while maintaining the manufacturer recommendation of a minimum 2 L/min of sweep gas to safely deliver NO without nitric dioxide (NO2) buildup. This setup was tested three times at three different FiO2 rates and eleven different desired low sweep flows to test for reproducibility and safety to build an easy-to-follow chart for making gas flow changes. For patients requiring oxygenator sweep rates greater than 2 L/min, the pressure relief valve/low flow meter apparatus is not needed. Maintaining consistent sweep rate and nitric oxide delivery is required in order to utilize this therapy in ECLS. We demonstrated gas delivery across all flow rates. There were no issues delivering 20 parts per million of NO and negligible NO2 detection. The results from testing this setup were used to provide the specialist a chart at which to set the low flow meter to produce the desired flow rate at which the patient needs. This has been used clinically on 15 ECLS patients with success.