BACKGROUND AND PURPOSE: The aim of the present study was to assess the time course
of hyperventilation (HV) and breath-holding (BH) tests in healthy volunteers. SUBJECTS
AND METHODS: Young healthy volunteers (n = 29) underwent continuous registration of
the middle cerebral artery mean blood flow velocity (MCAV) during and after 30 seconds
of BH and 60 seconds of HV. Absolute values as well as percentage changes of the MCAV
are reported. In 13 subjects, determination of capillary blood gas parameters (pH,
pCO2, pO2, and O2 saturation) was performed before tests, after BH and after HV. RESULTS:
MCAV during 30 seconds of breath-holding starts to increase after 10 seconds and reaches
its highest level at 30 seconds. After breathing normally, MCAV normalizes within
30 seconds. Hyper-ventilation results in a decrease in MCAV, which reaches a plateau
at 20 to 30 seconds after starting to hyperventilate, and blood flow velocity did
not change significantly any further until the end of the procedure. The normalization
of the MCAV is incomplete at 30 seconds after finishing hyperventilation. None of
the capillary blood gases changed significantly after breath-holding, whereas capillary
pH, pO2, and oxygen saturation increased and pCO2 decreased after hyperventilation.
No relationship was found between capillary blood gas parameters and MCAV values.
CONCLUSIONS: The authors concluded that breath-holding and hyperventilation tests
seem to be a practical alternative to acetazolamide and the CO2 inhalation method
in the assessment of cerebral hemodynamics.