Accumulation of carbon dioxide under ophthalmic drapes during eye surgery:a comparison of three different drapes

Carbon dioxide accumulation under ophthalmic drapes is caused by their impa ired permeability to exhaled carbon dioxide in spontaneously breathing pati ents. Three different ophthalmic drapes were examined under clinical condit ions. Sixty unpremedicated patients of each gender, aged over 60 years and with an ASA status of I-III undergoing cataract surgery under retrobulbar a naesthesia were included in the study. Patients with known pulmonary diseas es were excluded. The patients were divided into three groups of 20 patient s each. In all groups, oxygen was insufflated under the drapes at a constan t flow of 2 l.min(-1). Carbon dioxide concentration in the inspired air, tr anscutaneous carbon dioxide pressures, respiratory rate and oxygen saturati on by pulse oximetry were measured. Accumulation of carbon dioxide under th e drapes, increase of partial pressure of transcutaneous carbon dioxide and hyperventilation were observed in all three groups. An oxygen supply of 2 l.min(-1) prevented hypoxaemia but not hypercapnia. Therefore, producers of ophthalmic drapes are encouraged to look for further ways to increase the carbon dioxide permeability of their drapes with the aim of reducing carbon dioxide accumulation and hyperventilation in spontaneously breathing patie nts undergoing eye surgery.