Targeting arterial partial pressure of carbon dioxide in acute respiratory distress syndrome patients using extracorporeal carbon dioxide removal

Background: A retrospective analysis of SUPERNOVA trial data showed that reductions in tidal volume to ultraprotective levels without significant increases in arterial partial pressure of carbon dioxide (PaCO₂ ) for critically ill, mechanically ventilated patients with acute respiratory distress syndrome (ARDS) depends on the rate of extracorporeal carbon dioxide removal (ECCO₂ R).

Methods: We used a whole-body mathematical model of acid-base balance to quantify the effect of altering carbon dioxide (CO₂ ) removal rates using different ECCO₂ R devices to achieve target PaCO₂ levels in ARDS patients. Specifically, we predicted the effect of using a new, larger surface area PrismaLung+ device instead of the original PrismaLung device on the results from two multicenter clinical studies in critically ill, mechanically ventilated ARDS patients.

Results: After calibrating model parameters to the clinical study data using the PrismaLung device, model predictions determined optimal extracorporeal blood flow rates for the PrismaLung+ and mechanical ventilation frequencies to obtain target PaCO₂ levels of 45 and 50 mm Hg in mild and moderate ARDS patients treated at a tidal volume of 3.98 ml/kg predicted body weight (PW). Comparable model predictions showed that reductions in tidal volumes below 6 ml/kg PBW may be difficult for acidotic highly severe ARDS patients with acute kidney injury and high CO₂ production rates using a PrismaLung+ device in-series with a continuous venovenous hemofiltration device.

Conclusions: The described model provides guidance on achieving target PaCO₂ levels in mechanically ventilated ARDS patients using protective and ultraprotective tidal volumes when increasing CO₂ removal rates from ECCO₂ R devices.