Ventilation according the open lung concept attenuates pulmonary dysfunction after cardiac surgery

Introduction

After cardiac surgery, pulmonary dysfunction may develop as shown by a significant reduction of functional residual capacity (FRC) after extubation [1]. We hypothesized that ventilation according to the open lung concept (OLC) attenuates FRC reduction after extubation.

Methods

Sixty-three patients undergoing cardiopulmonary bypass were randomly assigned into three groups: conventional mechanical ventilation (CMV); OLC before, during and after cardiothoracic surgery (early open lung [EOL]); and CMV during surgery, OLC on the intensive care unit (late open lung [LOL]). The CMV group was ventilated with low tidal volume (6–8 ml/kg) with 5 cmH₂O PEEP. During OLC ventilation, recruitment maneuvers were applied until PaO₂/FiO₂ was above 50 kPa. This was maintained by the use of sufficient levels of PEEP. FRC was measured preoperatively and 1, 3 and 5 days after extubation. Peripheral oxygen saturation (SpO₂) was measured after extubation, breathing room air. SpO₂ < 91% was defined as hypoxia. Serum IL-8 was measured after aortic cross-clamp release. The variables were compared using analysis of variance for repeated measurements.

Results

Compared with the CMV group, FRC was significantly higher in the EOL group. In the LOL group, FRC was only significantly higher than the CMV group on the first day after extubation. In the CMV group, 37% of the patients were hypoxic on the third day after extubation, whereas none of the patients of both OLC groups. After release of the aortic cross clamp, IL-8 decreased significantly faster in the early OLC group compared with the CMV group.

Conclusion

Especially early application of the OLC group attenuated postoperative pulmonary dysfunction, measured by FRC and the occurrence of postoperative hypoxemia. This is probably founded on an attenuated pulmonary inflammation, as shown by a faster decrease of serum IL-8 concentration during early application of OLC.