Serial monitoring of CO2 reactivity following sport concussion using hypocapnia and hypercapnia

Brain Inj. 2013;27(3):346-53. doi: 10.3109/02699052.2012.743185.


Primary objective: This study examined the effects of mild traumatic brain injury (mTBI) on cerebrovascular reactivity (CVR).

Research design: A repeated measures design was used to examine serial changes in CVR.

Methods and procedures: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Athletic Injuries / blood*
  • Athletic Injuries / epidemiology
  • Athletic Injuries / physiopathology
  • Blood Flow Velocity
  • Brain Concussion / blood*
  • Brain Concussion / epidemiology
  • Brain Concussion / physiopathology
  • Canada / epidemiology
  • Carbon Dioxide / blood*
  • Cerebrovascular Circulation
  • Female
  • Humans
  • Hypercapnia / blood*
  • Hypercapnia / physiopathology
  • Hyperventilation / blood*
  • Hyperventilation / physiopathology
  • Hypocapnia / blood*
  • Hypocapnia / physiopathology
  • Male
  • Monitoring, Physiologic
  • Recovery of Function
  • Reproducibility of Results
  • Ultrasonography, Doppler, Transcranial
  • Vascular Resistance


  • Carbon Dioxide