Reflection of differential pulmonary perfusion in polytrauma patients on differential lung ventilation (DLV)

Seventeen polytrauma patients with asymmetric pulmonary contusion were treated with differential lung ventilation (DLV). The ratios of differential values of end-tidal CO₂ concentration (ETCO₂) and CO₂ excretion ml/min () were compared as indirect parameters for differential pulmonary perfusion. Both CO₂-derived methods indicated asymmetry after starting DLV suggesting asymmetric pulmonary perfusion as a consequence of contusion. Prior to stopping DLV a significant improvement in asymmetry was indicated by the differential ratios of ETCO₂ and values. The ETCO₂ ratio increased from 0.74±0.17 to 0.88±0.10, the ratio from 0.57±0.23 to 0.86±0.11. In two patients with very severe contusion who underwent bilobectomies a marked difference between the ratios of ETCO₂ and was observed. It is concluded that differential measurement of CO₂-derived variables may be useful in indicating differential perfusion in clinical practice on DLV. In very severe asymmetric contusion ETCO₂ ratios may underestimate the differential perfusion ratio.