LUNG AERATION - THE EFFECT OF PRE-OXYGENATION AND HYPEROXYGENATION DURING TOTAL INTRAVENOUS ANESTHESIA

We have investigated the effect of pre-oxygenation and hyperoxygenatio n (an increase in inspired oxygen fraction from 0.4 to 1.0 after induc tion of general anaesthesia) on aeration and atelectasis formation in the lungs during total intravenous anaesthesia. Twenty-seven consecuti ve patients were randomly allocated to group I (with pie-oxygenation), group 2 (without pre-oxygenation), or group 3 (hyperoxygenation). Lun g aeration was, investigated by means of spiral computed tomography. T he aeration of lung legions identified by computed tomography scans wa s divided into five categories. over-aeration, normal aeration, reduce d aeration, poor aeration, and atelectasis formation. In group 1 large r areas of atelectasis were found in the basal parts of the lungs comp ared to group 2. In group 3 a significant increase in atelectatic area s with a corresponding reduction in areas with reduced aeration occurr ed at the bases of the lungs. The considerable increase in atelectasis associated with pre-oxygenation and its rapid appearance during hyper oxygenation suggest that these procedures should be used with caution.