Oxygen delivery during endobronchial anaesthesia: a comparison of halothane-oxygen and nitrous oxide-oxygen

Total oxygen delivery (cardiac output X arterial oxygen content) and oxygen consumption were determined in 22 patients undergoing one-lung ventilation (OLV) during thoracotomy. In 11 patients, anaesthesia was maintained with halothane-oxygen and in another 11 patients with nitrous oxide-oxygen-analgesic combination (FIO2 0.5). During OLV, oxygen delivery was greater in the halothane group and these patients tended to show a decrease in oxygen consumption compared with the patients of the nitrous oxide group. Therefore, as far as total oxygen balance (oxygen delivery/oxygen consumption) during OLV is concerned, halothane-oxygen maintenance provides a greater margin of safety than nitrous oxide-oxygen-analgesic combination. However, in spite of occasional hypoxaemic episodes, none of our patients receiving 50% nitrous oxide in oxygen showed an oxygen delivery coefficient (oxygen delivery/oxygen consumption) significantly smaller than the predicted normal value for an unanaesthetized patient. This finding may explain why this anaesthetic technique has been used without apparent harm during OLV in patients with unimpaired cardiovascular function.