Dynamic cerebral autoregulation is acutely impaired during maximal apnoea in trained divers.
OBJECTIVE
To examine whether dynamic cerebral autoregulation is acutely impaired during maximal voluntary apnoea in trained divers.


METHODS
Mean arterial pressure (MAP), cerebral blood flow-velocity (CBFV) and end-tidal partial pressures of O2 and CO2 (PETO2 and PETCO2) were measured in eleven trained, male apnoea divers (28 ± 2 yr; 182 ± 2 cm, 76 ± 7 kg) during maximal "dry" breath holding. Dynamic cerebral autoregulation was assessed by determining the strength of phase synchronisation between MAP and CBFV during maximal apnoea.


RESULTS
The strength of phase synchronisation between MAP and CBFV increased from rest until the end of maximal voluntary apnoea (P<0.05), suggesting that dynamic cerebral autoregulation had weakened by the apnoea breakpoint. The magnitude of impairment in dynamic cerebral autoregulation was strongly, and positively related to the rise in PETCO2 observed during maximal breath holding (R (2) = 0.67, P<0.05). Interestingly, the impairment in dynamic cerebral autoregulation was not related to the fall in PETO2 induced by apnoea (R (2) = 0.01, P = 0.75).


CONCLUSIONS
This study is the first to report that dynamic cerebral autoregulation is acutely impaired in trained divers performing maximal voluntary apnoea. Furthermore, our data suggest that the impaired autoregulatory response is related to the change in PETCO2, but not PETO2, during maximal apnoea in trained divers.
Griffith Health Institute and Heart Foundation Research Centre, Griffith University, Gold Coast Campus, Queensland, Australia ; Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America.
Troy J
TJ
Cross
Griffith Health Institute and Heart Foundation Research Centre, Griffith University, Gold Coast Campus, Queensland, Australia.
Justin J
JJ
Kavanagh
Department of Physiology, University of Split School of Medicine, Split, Croatia.
Toni
T
Breskovic
Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America.
Bruce D
BD
Johnson
Department of Physiology, University of Split School of Medicine, Split, Croatia.
Zeljko
Z
Dujic
D000328:Adult; D001049:Apnea / Q000503:physiopathology*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004242:Diving / Q000502:physiology*; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D012129:Respiratory Function Tests; D017585:Ultrasonography, Doppler, Transcranial
D002245:Carbon Dioxide; D010100:Oxygen