Up to a third of ex-preterm infants flying near term exhibit pulse oxygen saturation (SpO2) of less than 85% during air travel. A hypoxia challenge test (HCT) is recommended to evaluate the requirement for in-flight supplemental O2. The validity of the HCT in healthy, term infants has not been reported. This study aimed to characterise the in-flight hypoxia response and the accuracy of the HCT to predict this response in healthy, term infants in the first year of life. Infants (n=24: (15 male)) underwent a HCT prior to commercial air travel during which parents monitored SpO2. Thirty-two flights were undertaken with six infants completing multiple flights. The median in-flight SpO2 nadir was 87% and significantly lower than the HCT SpO2 nadir (92%: p<0.001). Infants on seven flights recorded SpO2<85% with one infant recording a HCT with a SpO2 less than 85%. There was marked variability in the in-flight SpO2 in the six infants who undertook multiple flights, and for three of these infants, the SpO2 nadir was both above and below 85%. We report that in healthy term infants an in-flight SpO2 below 85% is common and can vary considerably between flights and that the HCT poorly predicts the risk of in-flight hypoxia (SpO2<85%). As it is common for healthy term infants to have SpO2 less than 85% during air travel further research is needed to clarify whether this is an appropriate cut-off in this age group.
- Paediatric Lung Disaese
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Commercial aircrafts are pressurised to a maximum altitude of 2400 m during air travel resulting in a partial oxygen (O2) pressure equivalent to 15–17% compared with 21% at sea level.1 In healthy children and adults pulse oxygen saturation (SpO2) declines to 89–94% during flight.2 There are only limited reports of the in-flight hypoxia response in healthy infants.
The hypoxia challenge test (HCT) is used to evaluate the requirement for in-flight supplemental O2 and involves monitoring SpO2 while inhaling a fractional inspired O2 concentration of ∼15%.1 Preterm infants less than 1 year should use in-flight supplemental O2 if the SpO2 decreases to <85% during the HCT.1 We have reported that preterm neonates flying near term exhibit hypoxia and that the HCT is unreliable.3 The validity of the HCT in older infants has not been reported. This study aimed to characterise the in-flight hypoxia response and the accuracy of the HCT in healthy infants in the first year of life.
We recruited 24 healthy term infants (15 male) aged 2.3–44.6 weeks. Infants underwent a HCT3 ,4 prior to commercial air travel. Parents monitored in-flight SpO2 (WristOx 3100; Nonin, Minnesota, USA) and activity state. Ethical approval was received (Princess Margaret Hospital for Children Ethics Committee: 1533/EP) and written consent obtained.
Thirty-two flights were undertaken with six infants completing multiple flights. Activity was recorded in 26 (81%) flights with 14 infants being asleep and the remainder being awake with no differences in the in-flight SpO2 nadir in sleeping infants compared with awake infants (data not shown). The median (range) HCT SpO2 nadir was 92% (82–98%) with one infant recording a SpO2<85%. The median in-flight SpO2 nadir was 87% (78–94%) and significantly lower than the HCT SpO2 nadir (Wilcoxon signed rank test: p<0.001). Infants on 25 flights were classified as passing the HCT and maintaining their in-flight SpO2 above 85%. Infants on seven flights (21.9%) recorded SpO2<85%, with only one infant recording a HCT with a SpO2<85%. There was marked in-flight SpO2 variability in the six infants who undertook multiple flights (table 1). One infant (infant 1) maintained SpO2 >85% on two flights with the remaining infants recording SpO2 nadirs from 78% to 90%. In this study, healthy term infants recorded in-flight SpO2 below 85% in seven of 32 flights (22%). In those infants with multiple flights, the SpO2 nadir varied between flights and for three (50%) infants the SpO2 nadir was both above and below 85%. Additionally, the HCT only correctly predicted one of seven infants as at risk for in-flight hypoxia (SpO2<85%). The impact of postnatal changes to oxygen transport through a reduction in oxygen affinity and oxygen carrying capacity5 may play a role in the variable in-flight behaviour of young infants and further research should explore these changes. As it is common for healthy term infants to have SpO2 less than 85% during air travel (without symptoms), further research clarifying the appropriateness of this cut-off is required.
Contributors All authors contributed to the interpretation of the data and preparation of the manuscript. CS, MV and GLH collected the study data. MV, ACW, MS and GLH devised and planned the study.
Funding This study was funded by the Princess Margaret Hospital Foundation. G Hall is funded by the National Health and Medical Research Council. There was no other involvement of funding bodies in the planning or conduct of the trial.
Competing interests None.
Patient consent Obtained.
Ethics approval Princess Margaret Hospital for Children Human Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.