title: Serial monitoring of CO2 reactivity following sport concussion using hypocapnia and hypercapnia.
abstract: OBJECTIVE
  This study examined the effects of mild traumatic brain injury (mTBI) on cerebrovascular reactivity (CVR).
  
  
  METHODS
  A repeated measures design was used to examine serial changes in CVR.
  
  
  METHODS
  Twenty subjects who recently suffered a mTBI were subjected to a respiratory challenge consisting of repeated 20 s breath-holds (BH) and hyperventilations (HV). Testing occurred on days 2 (D2), 4 (D4) and 8 (D8) post-injury as well as a baseline (BASE) assessment (after return-to-play). Transcranial Doppler was used to assess mean cerebral blood velocity (vMCA) and expired gas analysis provided end-tidal carbon dioxide (PETCO2) levels.
  
  
  RESULTS
  There was no significant difference in resting vMCA across all testing days for mTBI. No significant differences in PETCO2 were found throughout the testing protocol. A significant effect (p < 0.001) of testing day on vMCA was found during BH and HV challenges for mTBI. Post-hoc analysis revealed significant differences (p < 0.05) in vMCA between D2 and the other testing days.
  
  
  CONCLUSIONS
  These data suggest that, following mTBI: (1) CVR is not impaired at rest; (2) CVR is impaired in response to respiratory stress; and (3) the impairment may be resolved as early as 4 days post-injury.
authors: Faculty of Kinesiology and Health Studies, University of Regina, Saskatchewan, Canada.
authors: Trevor K
authors: TK
authors: Len
authors: J Patrick
authors: JP
authors: Neary
authors: Gordon J G
authors: GJ
authors: Asmundson
authors: Darren G
authors: DG
authors: Candow
authors: David G
authors: DG
authors: Goodman
authors: Bruce
authors: B
authors: Bjornson
authors: Yagesh N
authors: YN
authors: Bhambhani
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000097:blood* / Q000453:epidemiology / Q000503:physiopathology; D001783:Blood Flow Velocity; D001924:Brain Concussion / Q000097:blood* / Q000453:epidemiology / Q000503:physiopathology; D002170:Canada / Q000453:epidemiology; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000097:blood* / Q000503:physiopathology; D006985:Hyperventilation / Q000097:blood* / Q000503:physiopathology; D016857:Hypocapnia / Q000097:blood* / Q000503:physiopathology; D008297:Male; D008991:Monitoring, Physiologic; D020127:Recovery of Function; D015203:Reproducibility of Results; D017585:Ultrasonography, Doppler, Transcranial; D014655:Vascular Resistance
chemical_list: D002245:Carbon Dioxide