Influences of pleural effusion on respiratory mechanics,gas exchange,hemodynamics, and recruitment effects in acute respiratory distress syndrome

Background

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) cause substantial morbidity and mortality despite improvements in the understanding of lung injury and advances in treatment. Recruitment maneuver (RM) with high sustained airway pressures is proposed as an adjunct to mechanical ventilation to maintain alveolar patency. In addition, RM has been advocated to improve pulmonary gas exchange. However, many factors may influence responses to RM and the effect of pleural effusion (PLE) is unknown.

Method

There were four groups in this study (n = 6 in each group). Group A was the control group, group B was the PLE group, group C was ARDS with RM, and group D was ARDS with PLE and RM. RM was performed in groups C and D, consisting of a peak pressure of 45 cm H₂O with positive end-expiratory pressure of 35 cm H₂O sustained for 1 min. Arterial blood gas, systemic and pulmonary hemodynamics, lung water, and respiratory mechanics were measured throughout.

Result

After the induction of ALI/ARDS, there were significant decreases in partial pressure of oxygen in arterial blood, mean arterial pressure, systemic vascular resistance, and lung compliance. There were also significant increases in the alveolar–arterial O₂ tension difference, partial pressure of arterial carbon dioxide, mean pulmonary arterial pressure, pulmonary vascular resistance, and lung water. The RM improved oxygenation, which was attenuated by PLE.

Conclusions

ALI/ARDS leads to poor oxygenation and hemodynamics. RM results in improved oxygenation, but this improvement is attenuated by PLE.