Progressive changes in arterial oxygenation during one-lung anaesthesia are related to the response to compression of the non-dependent lung

Abstract

Background. Arterial oxygenation can change during one-lung ventilation for reasons that are not fully understood. Methods. We studied patients during anaesthesia and one-lung ventilation, with an inspiratory oxygen fraction of 0.8. Arterial blood gas values were recorded every 10 s with a continuous intra-arterial sensor. The non-dependent lung was compressed several times during the surgical procedure, using a retractor. The change in PaO2, during and after compression of the non-dependent lung was measured. Results. PaO2, increased significantly when the non-dependent lung was compressed, and decreased when the compression was released. The first compression of the non-dependent lung transiently increased PaO2, but the effect of the second compression on oxygenation was more marked and persistent. PaO2 increased by more than 13 kPa at 10 min after the second compression in four patients (responder group). Arterial oxygenation improved markedly in patients in this group during the surgical procedure. Conclusion. Oxygenation can improve during one-lung ventilation in some patients. This improvement is partly related to a marked increase in PaO2, during compression of the non-dependent lung.