Feasibility of a pumpless extracorporeal respiratory assist device

Background: Our study evaluated the efficacy and feasibility of a pumpless respiratory assist device and determined its capacity for carbon dioxide re moval. Methods: In five adult pigs the left femoral vein and artery were cannulate d with a 20F cannula and connected to a low-pressure hollow-fiber artificia l lung. After we had obtained baseline values of mean arterial pressure, ca rdiac output, and blood flow across the artificial lung, the mean arterial pressure was reduced 20% and 40% relative to baseline; in a second phase, i t was raised 20% and 40. Cardiac output and artificial lung flow were simul taneously recorded. We determined the carbon dioxide removal capacity of th e artificial lung by gradually increasing the arterial partial carbon dioxi de tension of the animal. Results: An increase of 10 mm Hg in mean arterial pressure resulted in an i ncrease of flow of 0.14 L/min. The mean pressure drop across the artificial lung was measured at 17 +/- 9 mm Hg. The shunt flow over the artificial lu ng varied between 14 and 25% of the cardiac output of the animal. Depending on inlet conditions, carbon dioxide removal by the artificial lung was bet ween 62 +/- 22. mL/L/min and 104 +/- 25 ML/L/min. Conclusions: A pumpless respiratory assist device can remove a significant proportion of the metabolic carbon dioxide production. However, adequate me an arterial pressure is mandatory to maintain sufficient flow across the de vice. The technique seems attractive because of its simplicity and can be u sed in acute lung injury in conjunction of apneic oxygenation for prolonged respiratory support.