title: Temporal dynamics of lactate concentration in the human brain during acute inspiratory hypoxia.
abstract: OBJECTIVE
  To demonstrate the feasibility of measuring the temporal dynamics of cerebral lactate concentration and examine these dynamics in human subjects using magnetic resonance spectroscopy (MRS) during hypoxia.
  
  
  METHODS
  A respiratory protocol consisting of 10-minute baseline normoxia, 20-minute inspiratory hypoxia, and ending with 10-minute normoxic recovery was used, throughout which lactate-edited MRS was performed. This was repeated four times in three subjects. A separate session was performed to measure blood lactate. Impulse response functions using end-tidal oxygen and blood lactate as system inputs and cerebral lactate as the system output were examined to describe the dynamics of the cerebral lactate response to a hypoxic challenge.
  
  
  RESULTS
  The average lactate increase was 20% ± 15% during the last half of the hypoxic challenge. Significant changes in cerebral lactate concentration were observed after 400 seconds. The average relative increase in blood lactate was 188% ± 95%. The temporal dynamics of cerebral lactate concentration was reproducibly demonstrated with 200-second time bins of MRS data (coefficient of variation 0.063 ± 0.035 between time bins in normoxia). The across-subject coefficient of variation was 0.333.
  
  
  CONCLUSIONS
  The methods for measuring the dynamics of the cerebral lactate response developed here would be useful to further investigate the brain's response to hypoxia.
authors.affiliation: Cardiff University Brain Imaging Research Centre, School of Psychology, Cardiff University, Cardiff, UK. Harrisa6@cardiff.ac.uk
authors.forename: Ashley D
authors.initials: AD
authors.lastname: Harris
authors.forename: Victoria H
authors.initials: VH
authors.lastname: Roberton
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Huckle
authors.forename: Neeraj
authors.initials: N
authors.lastname: Saxena
authors.forename: C John
authors.initials: CJ
authors.lastname: Evans
authors.forename: Kevin
authors.initials: K
authors.lastname: Murphy
authors.forename: Judith E
authors.initials: JE
authors.lastname: Hall
authors.forename: Damian M
authors.initials: DM
authors.lastname: Bailey
authors.forename: Georgios
authors.initials: G
authors.lastname: Mitsis
authors.forename: Richard A E
authors.initials: RA
authors.lastname: Edden
authors.forename: Richard G
authors.initials: RG
authors.lastname: Wise
mesh_terms: D000208:Acute Disease; D000328:Adult; D001921:Brain / Q000473:pathology*; D005260:Female; D006801:Humans; D000860:Hypoxia; D002534:Hypoxia, Brain / Q000473:pathology*; D007773:Lactates / Q000097:blood / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D015233:Models, Statistical; D010100:Oxygen / Q000737:chemistry; D012119:Respiration; D013997:Time Factors
chemical_list: D007773:Lactates; D019344:Lactic Acid; D010100:Oxygen