title: The Young Everest Study: preliminary report of changes in sleep and cerebral blood flow velocity during slow ascent to altitude in unacclimatised children.
abstract: BACKGROUND
  Cerebral blood flow velocity (CBFV) and sleep physiology in healthy children exposed to hypoxia and hypocarbia are under-researched.
  
  
  OBJECTIVE
  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 (R(2) 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 (R(2) 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.
authors.affiliation: 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@gosh.nhs.uk
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Gavlak
authors.forename: Janet
authors.initials: J
authors.lastname: Stocks
authors.forename: Aidan
authors.initials: A
authors.lastname: Laverty
authors.forename: Emma
authors.initials: E
authors.lastname: Fettes
authors.forename: Romola
authors.initials: R
authors.lastname: Bucks
authors.forename: Samatha
authors.initials: S
authors.lastname: Sonnappa
authors.forename: Janine
authors.initials: J
authors.lastname: Cooper
authors.forename: Michael P
authors.initials: MP
authors.lastname: Grocott
authors.forename: Denny Z
authors.initials: DZ
authors.lastname: Levett
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Martin
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Imray
authors.forename: Fenella J
authors.initials: FJ
authors.lastname: Kirkham
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000293:Adolescent; D000531:Altitude; D001783:Blood Flow Velocity / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002648:Child; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D016857:Hypocapnia / Q000097:blood / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology; D008297:Male; D009390:Nepal; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000097:blood; D012890:Sleep / Q000502:physiology*; D014195:Travel; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen