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[The normal values of the haemodynamic reserve (HR) evaluated by the CO2 test].

BACKGROUND
The cerebral haemodynamic reserve (HR) is a recognised predictive factor of brain ischaemia in subjects with carotid stenosis. Our objective is to establish normal parameters which may be used for comparison with deficit states.


SUBJECTS AND METHOD
The haemodynamic reserve was calculated in healthy subjects who had no evidence of previous carotid, haematological or cardiovascular pathologies. Subjects were asked to inhale CO2. The HR was then calculated as a percentage of the increase in the mean velocity in the Silvian artery for each millimetre of mercury increase of the end-tidal CO2. The median and percentiles 5 and 95 were calculated for each hemisphere, sex and age group.


RESULTS
100 subjects were studied (45 men and 55 women, mean age 51.6 years, range 18-79). Normal HR value was defined as percentile 5, with a value of 2% for men, and 2.5% for women. The only adverse reaction was dyspnea in 2 subjects.


CONCLUSIONS
Values for the haemodynamic reserve of healthy subjects, which may serve as a reference for other ultrasonography laboratories, are established from an extensive control group.