Oxygen application by a nasal probe prevents hypoxia but not rebreathing of carbon dioxide in patients undergoing eye surgery under local anaesthesia

Abstract

Background/aim - Hypoxia and carbon dioxide rebreathing are potential problems during eye surgery in spontaneously breathing patients. The aim of the present study was to determine effectiveness of nasal application of oxygen to prevent hypoxia and carbon dioxide accumulation in spontaneously breathing patients undergoing cataract surgery. Methods - Oxygenation and carbon dioxide rebreathing were examined in 40 elderly patients using two different methods of oxygen supply - nasal v ambient air - with a constant flow of 2 l/min. Partial pressure of carbon dioxide under ophthalmic drapes, transcutaneous pressure of carbon dioxide, and the respiratory rate were measured during 25 minutes while oxygen was supplied via a nasal cannula or into the ambient air under the drapes. Results - In both groups carbon dioxide accumulation under the drapes, carbon dioxide rebreathing, tachypnoea, and an increase in peripheral oxygen saturation occurred. No significant differences were found between the two methods. Conclusion - Nasal application of oxygen prevented hypoxia but did not prevent carbon dioxide accumulation in patients undergoing eye surgery under retrobulbar anaesthesia. Additionally, as a side effect when using nasal probes, irritation of the nose was described in half of the patients investigated.