Noninvasive Monitoring of Dynamic Cerebrovascular Autoregulation and 'Optimal Blood Pressure' in Normal Adult Subjects.

BACKGROUND

Cerebrovascular autoregulation can be continuously monitored from slow fluctuations of arterial blood pressure (ABP) and regional cerebral oxygen saturation (rSO). The purpose of this study was to evaluate the index of dynamic cerebrovascular autoregulation (TOx) and the associated 'optimal' ABP in normal adult healthy subjects.

METHODS

Twenty-eight healthy volunteers were studied. TOx was calculated as the moving correlation coefficient between spontaneous fluctuations of ABP and rSO. ABP was measured with the Finometer photoplethysmograph. The ABP with optimal autoregulation (ABP) was also determined as the ABP level with the lowest associated TOx (opt-TOx).

RESULTS

Average rSO and TOx was 72.3 ± 2.9% and 0.05 ± 0.18, respectively. Two subjects had impaired autoregulation with a TOx > 0.3. The opt-TOx was - 0.1 ± 0.26. ABP was 87.0 ± 16.7 mmHg. The difference between ABP and ABP was - 0.3 ± 7.5 mmHg. In total, 44% of subjects had a deviation of ABP from ABP exceeding 5 mmHg. ABP ranged from 57 to 117 mmHg.

CONCLUSIONS

TOx in healthy volunteers on average displays intact autoregulation and ABP close to ABP. However, some subjects have possible autoregulatory dysfunction or a significant deviation of ABP from ABP, which may confer a susceptibility to neurological injury.