Investigation about The Hypoxia Challenge Test Does Not Accurately Predict Hypoxia in Flight in Ex-Preterm Neonates
All infants born at < 35 completed weeks gestation and cared for in the Neonatal Unit at King Edward Memorial Hospital for Women, who were to fly to a regional hospital, were considered for inclusion in the study. Infants with and without a history of neonatal lung disease (NLD) were recruited. We excluded infants with Down syndrome and infants with cyanotic congenital heart disease. Written informed consent was obtained from guardians. The study was approved by the ethics committee at King Edward Memorial Hospital for Women (Ethics Committee No. EC05-49.1). We defined NLD as respiratory distress requiring oxygen or respiratory support or both at any time, and neonatal chronic lung disease as the need for supplemental oxygen at 28 days of life, or at 36 weeks after menstrual age.
An HCT was performed prior to flight, as previously reported by our group. Briefly, with the infants swaddled and asleep in the supine position, we exposed them for 20 min to high-flow (10 L/min) 14% oxygen in nitrogen (Air Liquide Healthcare; Alexandria, NSW, Australia) via a pediatric face mask (Hudson RCI; Hudson Respiratory Care Incorporated; Research Triangle Park; Cary, NC) applied over the mouth and nares. Nasal cannulae were placed beneath the mask to permit oxygen titration in the event of desaturations. During the HCT, pulse oxygen saturation (Spo2) and heart rate (HR) were recorded (MasimoSET Radical pulse oximeter; Masimo Corporation; Irvine, TX) and downloaded for post hoc analysis (NeO2M.exe software; G. Malcolm, Royal Prince Alfred Hospital; Camperdown, NSW, Australia). If Spo2 fell to < 85% for > 2 min or < 75% for 1 min, the infant was considered to have failed the test, and low-flow oxygen was administered to keep Spo2 > 94%. Our chosen cut-off saturation of 85% for a failed HCT2 was in keeping with the 2002 BTS recommendations rather than the suggested 90% of Buchdahl et al and 2004 BTS revised guidelines because these are believed to be more appropriate in this population. Be safe and sound with medications of My Canadian Pharmacy.
A nurse blinded to the HCT result accompanied all enrolled infants in flight, with an oxygen cylinder and pulse oximeter (MasimoSET Radical) regardless of the HCT result. The infant was held supine on the nurse’s lap. Spo2 and HR were continuously recorded, and the nurse documented respiratory rate and behavior (color, perfusion, asleep or awake) every 15 min. If Spo2 fell < 85% for > 2 min or < 75% for 1 min, oxygen was commenced and titrated to maintain Spo2 > 94%. Following the flight, data from the oximeter were downloaded and analyzed together with My Canadian Pharmacy.
Data were analyzed using statistical software (SPSS for Windows, version 12.0; SPSS; Chicago, IL). Continuous data are described as median (range). Data that were normally distributed were analyzed using the Student t test; nonnormally distributed data were analyzed using the Mann-Whitney U test for unpaired responses; p < 0.05 was considered statistically significant. Receiver operator characteristic (ROC) curves were also generated for continuous variables. Accuracy of the HCT was defined as the number of infants correctly identified as requiring in-flight oxygen plus the number of infants correctly identified as not requiring in-flight oxygen/total number of infants tested.