An Evaluation of the Relative Efficacy of an Open Airway,an Oxygen Reservoir and Continuous Positive Airway Pressure 5 cmH 2 O on the Non-ventilated Lung

The aim of this study, during one-lung ventilation, was to evaluate if oxygenation could be improved by use of a simple oxygen reservoir or application of 5 cmH₂O continuous positive airway pressure (CPAP) to the non-ventilated lung compared with an open airway. Twenty-three patients with lung malignancy, undergoing thoracotomy requiring at least 60 minutes of one-lung ventilation before lung lobe excision, were studied. After routine induction and establishment of one-lung ventilation, the three treatments were applied in turn to the same patient in a sequence selected randomly. The first treatment was repeated as a fourth treatment and these results of the repeated treatment averaged to minimize the effect of slow changes.

Arterial oxygenation was measured by an arterial blood gas 15 minutes after the application of each treatment. Twenty patients completed the study. Mean P_aO₂ (in mmHg) was 210.3 (SD 105.5) in the “OPEN” treatment, 186.0 (SD 109.2) in the “RESERVOIR” treatment, and 240.5 (SD 116.0) in the “CPAP” treatment. This overall difference was not quite significant (P=0.058, paired ANOVA), but comparison of the pairs showed that there was a significant better oxygenation only with the CPAP compared to the reservoir treatments (t=2.52, P=0.021). While the effect on the surgical field was not apparent in most patients, in one patient surgery was impeded during CPAP. Our results show that the use of a reservoir does not give oxygenation better than an open tube, and is less effective than the use of CPAP 5 cmH₂O on the non-ventilated lung during one-lung ventilation.