New equipment to prevent carbon dioxide rebreathing during eye surgery under retrobulbar anaesthesia

Background-Carbon dioxide concentration under ophthalmic drapes increases d uring eye surgery under local anaesthesia. A new prototype has been designe d which combines continuous suction of carbon dioxide enriched air and cont inuous oxygen insufflation under ophthalmic drapes to prevent carbon dioxid e accumulation in spontaneously breathing patients undergoing cataract surg ery. Methods-In a prospective randomised single blind study the effectiveness of this new prototype was examined in 50 unpremedicated elderly patients. In 25 patients suction was applied under ophthalmic drapes, whereas in the oth er 25 patients no suction was used. In all cases oxygen was insufflated und er the drapes at a constant flow of 2 1/min. Carbon dioxide concentration i n the ambient air surrounding the patient's head under ophthalmic drapes, t ranscutaneous partial pressure of carbon dioxide, respiratory rate, and oxy gen saturation were measured. Results-Carbon dioxide concentration under the drapes, transcutaneous parti al pressure of carbon dioxide, and respiratory rate remained unchanged in t he suction group, whereas in the non-suction group these values increased s ignificantly. Oxygen saturation rose significantly in both groups without d ifferences between the groups. Conclusion-Application of this new prototype for continuous aspiration of c arbon dioxide enriched air prevents carbon dioxide rebreathing and subseque nt hypercapnia associated with an elevated respiratory rate. This new equip ment may therefore be useful in patients undergoing ophthalmic surgery unde r retrobulbar anaesthesia.