Impact of Pulsatile Flow on Pulmonary Transvascular Fluid Flux During Veno-Pulmonary Arterial ECMO: A Pilot Ovine Study.

INTRODUCTION Although flow pulsatility has been suggested to confer physiological benefits in other forms of mechanical circulatory support, its role in veno-pulmonary arterial extracorporeal membrane oxygenation (VP ECMO) has not yet been investigated. We hypothesized that non-pulsatile flow into the pulmonary circulation during VP ECMO may promote pulmonary transvascular fluid flux, whereas pulsatile flow may attenuate these effects.

Methods

Six adult female sheep (41-53 kg) underwent VP ECMO and were randomly assigned to either non-pulsatile (n = 3) or pulsatile flow (n = 3) using an electrocardiogram (ECG)-synchronized cardiac system (SCS / iCOR, Xenios, Fresenius Medical Care, Germany) for 96 hours. The pulsatility was synchronized to heart rate by ECG. Lung lymph flow, pulmonary hemodynamics, extravascular lung water (EVLW), and histological findings were evaluated.

Results

ECMO blood flow was maintained at 2.0 L/min in both groups. Lung lymph flow increased progressively over time in the non-pulsatile flow group, reaching approximately 3- to 4-fold of baseline; no such increase was observed in the pulsatile group. Mixed-effects analysis demonstrated significantly higher lung lymph flow and mean pulmonary arterial pressure in the non-pulsatile group. EVLW and histological interstitial edema tended to be higher in the non-pulsatile group.

Conclusions

Non-pulsatile flow was associated with increased lung lymph flow and higher mean pulmonary arterial pressure in our pilot ovine study, whereas ECG-synchronized pulsatile flow appears to attenuate these changes. Further studies are warranted to investigate the role of pulsatile pulmonary arterial flow as a strategy to preserve pulmonary vascular fluid balance.