Monitoring differential CO2 excretion during differential lung ventilation in asymmetric pulmonary contusion. Clinical implications.

Eighteen severely injured polytrauma patients (ISS 38 +/- 18) with severe asymmetric pulmonary contusion were ventilated with differential lung ventilation (DLV) to improve oxygenation and/or to prevent further unnecessary barotrauma to the lesser involved lung. Differential VCO2 was studied as a parameter for indirect measurement of effective individual pulmonary perfusion. One hour after starting DLV, difference in differential VCO2 (delta VCO2) was 81 +/- 57 ml/min. In 16 patients this had fallen significantly (p less than 0.001) to 32 +/- 30 ml/min, 1 h before DLV was discontinued. In 2 patients, VCO2 remained greater than 200 ml/min, coinciding with clinical deterioration and increasing consolidation of the pulmonary contusion. Bilobectomies were performed in both patients. The excised lobes appeared to be destroyed as the result of laceration, bleeding and subsequent haematomas. This clinical study supports laboratory studies suggesting the usefulness of monitoring differential VCO2 to assess effective differential pulmonary perfusion during DLV.