Oxygenation during local anaesthesia for cataract surgery

The oxygenation of 48 elderly patients scheduled for cataract surgery under local anaesthesia was studied using pulse oximetry and nasopharyngeal oxygen measurement. After a control period the patients breathed supplemental oxygen 2 1/min and later 4 1/min, via either a face mask or a nasal catheter. The effects of the two oxygen flow levels and oxygen delivery methods on oxygenation were assessed. The lowest oxygen saturation values were seen after retrobulbar block before the patients were transferred to the operating room. The surgical draping did not cause hypoxaemia and the 2 1/min oxygen flow was sufficient to cause hyperoxaemia in all patients. The face mask and nasal catheter appeared to be equally good in oxygenating the patients.