Reduction of ventilator settings allowed by intravenous oxygenator (IVOX) in ARDS patients

Objective To evaluate the possibility of reducing ventilator settings to “safe” levels by extrapulmonary gas exchange with IVOX in ARDS patients. Design Uncontrolled open clinical study. Setting Medical Intensive Care Unit of a University Hospital. Patients 6 patients with ARDS who entered into IVOX phase II clinical trials. Interventions The end-point of this study was to reduce ventilator settings from the initial values, recorded on the day of inclusion, to the following: peak inspiratory pressure <40 cmH₂O, mean airway pressure <25 cmH₂O and tidal volume <10 ml/kg. Trials to achieve this goal were made on volume-controlled ventilation within the 24h before and after IVOX insertion. Comparison of the results achieved during these trials used wilcoxon test. Results Before IVOX implantation reduction of ventilator settings was not possible in the 6 patients, despite a non-significant increase in PaO₂/FIO₂ was achieved. IVOX permitted significant decrease in PaCO₂ (from 60.5±15 to 52±11 mmHg;p=0.02) before any modification of the ventilatory mode. After IVOX insertion, a significant decrease of the ventilator settings was performed: peak and mean airway pressures dropped from 44±10 to 36.8±6.7;p=0.02 and from 26.3±5.6 to 22.5±3.9 cmH₂O;p=0.02, respectively. Concommitantly, PaCO₂ remained unchanged and PaO₂/FIO₂ increased significantly from 93±28 to 117±52;p=0.04. The interruption of oxygen flow on IVOX was associated with a slight decrease of the oxygen variables. Tolerance of IVOX was satisfactory. However, a significant decrease both in cardiac index and in pulmonary wedge pressures (from 4.5±1.2 to 3.4±9;p=0.03 and from 16±5 to 11±2;p=0.04, respectively) was observed. Conclusion Gas exchange achieved by IVOX allowed reduction of ventilator settings in 6 ARDS patients in whom previous attempts have failed. CO₂ removal by the device, may explain these results. Efficacy of IVOX on arterial oxygenation was uncertain.