CASE HISTORY
61-year old male (height; 167 cm, weight; 67 kg, body surface area; 1.76 m2) with interstitial lung disease waiting for lung transplantation was supported by VV-ECMO because his pulmonary function was worsening. The cannulation was approached conventionally using percutaneous procedure via the right internal jugular (return) and right common femoral vein (drainage) using 15Fr and 23Fr HLS© cannulae (Maquet; Getinge Group, Rastatt, Germany). A terumo emergency bypass system (Terumo Corp., Tokyo, Japan) was used and the ECMO was set 3.80 liters per minute, 2400 rotations per minute, an inspired oxygen fraction of 1.0, and a sweep gas flow rate of 4.00 liters per minute. A 28% recirculation rate was measured by the ELSA®monitor (Transonic Systems Inc., Ithaca, NY, USA) , which measures the amount of recirculation using the ultrasound dilution technique (Fig. 1).4 Cardiac function and size, as measured by transthoracic echocardiography, were normal without pulmonary hypertension. We could maintain the protective ventilator setting, but flow disturbance occurred due to chatter in the venous drainage circuit when intrathoracic pressure was increased during suctioning in the endotracheal tube. When blood flow disturbance occurred, unpredictable volume was added to maintain ECMO flow because hypoxia was detected, therefore ventilator had to change to the higher tidal volume and plateau airway pressure than protective ventilation, occasionally.
Although the possibility of recirculation could become higher, we repositioned the drainage cannula at a higher level until SVC to maintain ECMO flow. Before positioning the drainage cannula, the recirculation rate was 26%. The first step of the repositioning procedure involved advancing the return cannula 2 cm, which increased the recirculation rate to 30%. Then, after advancing the return cannula 1cm additionally, a recirculation rate decreased to 24%, and the VV-ECMO flow was maintained stable. The next day, a recirculation rate was 14% after VV-ECMO flow was decreased from 4.4 to 4.0 LPM (Fig. 2). After 12 hospital days on VV-ECMO support, lung transplantation was performed successfully and the patient recovered well.