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The Young Everest Study: preliminary report of changes in sleep and cerebral blood flow velocity during slow ascent to altitude in unacclimatised children
  1. Johanna C Gavlak1,2,
  2. Janet Stocks2,
  3. Aidan Laverty1,
  4. Emma Fettes1,
  5. Romola Bucks3,
  6. Samatha Sonnappa1,2,
  7. Janine Cooper4,
  8. Michael P Grocott5,6,7,
  9. Denny Z Levett5,
  10. Daniel S Martin5,
  11. Christopher H Imray8,
  12. Fenella J Kirkham7,9,10
  1. 1Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
  2. 2Portex Respiratory Unit, UCL Institute of Child Health, London, UK
  3. 3Department of Psychology, University of Western Australia, Perth, Australia
  4. 4Developmental Neuroscience Unit, UCL Institute of Child Health, London, UK
  5. 5Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK
  6. 6Anaesthesia and Critical Care Research Unit, University Hospitals Southampton NHS Foundation Trust, Southampton, UK
  7. 7Department of Clinical and Experimental Sciences, University of Southampton, Southampton, UK
  8. 8Department of Vascular Surgery, University Hospitals Coventry and Warwickshire NHS Trust, Warwick Medical School, Coventry, UK
  9. 9Neurosciences Units, UCL Institute of Child Health, London, UK
  10. 10Department of Child Health, University Hospitals Southampton NHS Foundation Trust, Southampton, UK
  1. Correspondence to Dr Johanna C D Gavlak, Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Trust, Walrus Ward Level 1, Morgan Stanley Clinical Building, Great Ormond Street, London WC1N 3JH, UK; Johanna.Dingle-Gavlak{at}


Background Cerebral blood flow velocity (CBFV) and sleep physiology in healthy children exposed to hypoxia and hypocarbia are under-researched.

Aim To investigate associations between sleep variables, daytime end-tidal carbon dioxide (EtCO2) and CBFV in children during high-altitude ascent.

Methods Vital signs, overnight cardiorespiratory sleep studies and transcranial Doppler were undertaken in nine children (aged 6–13 years) at low altitude (130 m), and then at moderate (1300 m) and high (3500 m) altitude during a 5-day ascent.

Results Daytime (130 m: 98%; 3500 m: 90%, p=0.004) and mean (130 m: 97%, 1300 m: 94%, 3500: 87%, p=0.0005) and minimum (130 m: 92%, 1300 m: 84%, 3500 m: 79%, p=0.0005) overnight pulse oximetry oxyhaemoglobin saturation decreased, and the number of central apnoeas increased at altitude (130 m: 0.2/h, 1300 m: 1.2/h, 3500 m: 3.5/h, p=0.2), correlating inversely with EtCO2 (R2 130 m: 0.78; 3500 m: 0.45). Periodic breathing occurred for median (IQR) 0.0 (0; 0.3)% (130 m) and 0.2 (0; 1.2)% (3500 m) of total sleep time. At 3500 m compared with 130 m, there were increases in middle (MCA) (mean (SD) left 29.2 (42.3)%, p=0.053; right 9.9 (12)%, p=0.037) and anterior cerebral (ACA) (left 65.2 (69)%, p=0.024; right 109 (179)%; p=0.025) but not posterior or basilar CBFV. The right MCA CBFV increase at 3500 m was predicted by baseline CBFV and change in daytime SpO2 and EtCO2 at 3500 m (R2 0.92); these associations were not seen on the left.

Conclusions This preliminary report suggests that sleep physiology is disturbed in children even with slow ascent to altitude. The regional variations in CBFV and their association with hypoxia and hypocapnia require further investigation.

  • Transcranial Doppler
  • hypoxia
  • acute mountain sickness
  • altitude
  • Sleep

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