Predicting hypoxaemia during flights in children with cystic fibrosis

Background-We have previously suggested that it is possible to predict oxyg en desaturation during flight in children with cystic fibrosis and chronic lung disease by non-invasive measurement of oxygen saturation following inh alation of 15% oxygen-the pre-flight hypoxic challenge. This study reports on the results of measurements over 5 years. Methods-The study comprised a preflight hypoxic challenge measuring oxygen saturation by finger tip pulse oximetry (Spo(2)) during tidal breathing of 15% oxygen in nitrogen and spirometric testing 1 month before the flight fo llowed by Spo(2) measurements during intercontinental flights to and from h olidays abroad with children in wake and sleep states. Results-Pre-flight tests were completed on 87 children with cystic fibrosis . Desaturation of < 90% occurred in 10 children at some stage during the fl ight, three of whom received supplementary oxygen. Using a cut off Spo(2) o f 90%, the pre-flight hypoxic challenge correctly predicted desaturation in only two of these children. The sensitivity and specificity of the pre-fli ght hypoxic challenge were 20% and 99%, respectively, compared with 70% and 96% for spirometric tests (using a cut off for forced expiratory volume in second (FEV1) of < 50% predicted). Overall, preflight spirometric tests we re a better predictor of desaturation during flight with the area under the Receiver Operating Characteristic (ROC) curve of 0.89 compared with 0.73 f or the hypoxic challenge test. Conclusions-In this group of subjects pre-flight spirometric testing was a better predictor of desaturation during flight than the pre-flight hypoxic challenge.