Efficacy and safety of a low-flow veno-venous carbon dioxide removal device: results of an experimental study in adult sheep

INTRODUCTION: Extracorporeal lung assist, an extreme resource in patients with acute respiratory failure (ARF), is expanding its indications since knowledge about ventilator-induced lung injury has increased and protective ventilation has become the standard in ARF. METHODS: A prospective study on seven adult sheep was conducted to quantify carbon dioxide (CO(2)) removal and evaluate the safety of an extracorporeal membrane gas exchanger placed in a veno-venous pump-driven bypass. Animals were anaesthetised, intubated, ventilated in order to reach hypercapnia, and then connected to the CO(2 )removal device. Five animals were treated for three hours, one for nine hours, and one for 12 hours. At the end of the experiment, general anaesthesia was discontinued and animals were extubated. All of them survived. RESULTS: No significant haemodynamic variations occurred during the experiment. Maintaining an extracorporeal blood flow of 300 ml/minute (4.5% to 5.3% of the mean cardiac output), a constant removal of arterial CO(2), with an average reduction of 17% to 22%, was observed. Arterial partial pressure of carbon dioxide (PaCO(2)) returned to baseline after treatment discontinuation. No adverse events were observed. CONCLUSION: We obtained a significant reduction of PaCO(2 )using low blood flow rates, if compared with other techniques. Percutaneous venous access, simplicity of circuit, minimal anticoagulation requirements, blood flow rate, and haemodynamic impact of this device are more similar to renal replacement therapy than to common extracorporeal respiratory assistance, making it feasible not only in just a few dedicated centres but in a large number of intensive care units as well.