We measured certain respiratory conditions (respiratory rate [RR], oxygen saturation [SO2], and end-expiratory carbon dioxide partial pressure [pCO2]) of 31 patients undergoing planned cataract surgery using local anesthesia in order to determine the effects of administering pure oxygen (3 L/min) by a nasal probe in 10 of them. In the patients who did not receive pure oxygen, at the end of surgery the mean RR was 15.8 +/- 4.4/min (maximum, 21; minimum, 6.4/min); the mean SO2 was 86.9% +/- 6.6% (maximum, 98%; minimum, 74%; in 11/25 patients, the SO2 was lower than 90%); and the mean pCO2 was 34.9 +/- 7.7 mm Hg (maximum, 46.5; minimum, 12.15; in 4/25 patients, the pCO2 was greater than 45 mm Hg). In the patients who received pure oxygen by a nasal probe, the mean SO2 increased intraoperatively from 80.6% +/- 5.8% to 96.9 +/- 2.9% (in no patients was SO2 lower than 90%). Therefore we recommend an intraoperative administration of pure oxygen by a nasal probe.