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Hypoxic challenge test applied to healthy children: influence of body positions and exertion on pulse oximetric saturation
  1. Helene Elgaard Kobbernagel,
  2. Kim Gjerum Nielsen,
  3. Birgitte Hanel
  1. Paediatric Pulmonary Service, Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
  1. Correspondence to Dr Kim Gjerum Nielsen, Paediatric Pulmonary Service, Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen DK-2100, Denmark; kgn{at}dadlnet.dk

Abstract

Background Commercial aircraft are pressurised to ∼2438 m (8000 ft) above sea level that equates breathing 15% oxygen at sea level. A preflight hypoxic challenge test (HCT) is therefore recommended for children with cystic fibrosis or other chronic lung diseases and inflight oxygen is advised if pulse oximetric saturation (SpO2) decreases <90%.

Objective Study responses to a modified HCT, encompassing various body positions and light physical activity, reflecting relevant activities of children during flight, with a view to challenge the evidence of the current cut-off.

Methods Oxygenation, heart rate and ventilation were observed in 34 healthy schoolchildren (17 boys) undergoing a modified HCT, alternating between breathing room air and 15% oxygen in nitrogen while seated, supine, standing and walking at 3 km/h and 5 km/h.

Results Nadir SpO2 <90%, median (range), occurred in 9 subjects sitting, 89% (78–89%); 6 supine, 88.5% (87–89%); 9 standing, 89% (85–89%); 23 walking 3 km/h, 87% (74–89%); and 21 walking 5 km/h, 86% (74–89%). Total time <90% for these subjects in seconds was 20 (10–80) sitting, 30 (10–190) supine, 50 (10–150) standing, 80 (10–260) walking 3 km/h and 125 (10–300) walking 5 km/h. Light exercise in general led to lower SpO2: 91% (77–96%), p<0.0001.

Conclusions A modified HCT led to moments of desaturation below 90% in various body positions at rest and during light physical activity in healthy schoolchildren. It is questionable whether the international recommended cut-off of 90% for children with chronic lung disease reflects clinical oxygen dependence during flights.

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