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Original scientific paper
Breath Holding Index in the Evaluation of Cerebral Vasoreactivity
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Pages 15 - 19
The aim of the study was to assess normal values of the middle cerebral artery breath holding index in healthy males and females. Healthy volunteers (180 male and 180 female) were divided into 6 age groups for each sex. All basal cerebral arteries were evaluated by transcranial Doppler in a standardized manner. Breath holding method was used in the evaluation of cerebrovascular vasoreactivity in the middle cerebral artery and 720 values of breath holding index were obtained. The middle cerebral artery mean velocity was continuously monitored for at least 5 minutes to obtain baseline values. Breath was held for 20-30 seconds and mean blood flow velocities during the last 3 seconds of breath hold were taken in calculation as a V max velocity value. Breath holding index was calculated as percent of velocity increase from resting baseline values divided by breath holding time. The values of breath holding index were calculated for all subjects and for each sex separately. Statistical analysis was performed by nonparametric χ2 and Fisher tests (statistical significance was set at p<0.05). Variation coefficient for each age group and Pearson's linear correlation coefficient for mean blood flow velocity and breath holding index values were calculated. The majority (95%) of subjects were in the group of breath holding index values within the range of 1.03-1.65. There was no statistically significant decrease in breath holding index values with age (p>0.05), however, an age dependent decrease in the mean blood flow velocity was recorded in all subjects (p<0.01). Breath holding index is a nonaggressive, well tolerated, real-time, reproducible screening method to study cerebral hemodynamics.
Cerebrovascular circulation - physiology; Respiration - physiology; Blood vessels - ultrasonography