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 (rSO₂). 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 rSO₂. ABP was measured with the Finometer photoplethysmograph. The ABP with optimal autoregulation (ABP_OPT) was also determined as the ABP level with the lowest associated TOx (opt-TOx). Results: Average rSO₂ 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_OPT was 87.0 ± 16.7 mmHg. The difference between ABP and ABP_OPT was − 0.3 ± 7.5 mmHg. In total, 44% of subjects had a deviation of ABP from ABP_OPT exceeding 5 mmHg. ABP_OPT ranged from 57 to 117 mmHg. Conclusions: TOx in healthy volunteers on average displays intact autoregulation and ABP close to ABP_OPT. However, some subjects have possible autoregulatory dysfunction or a significant deviation of ABP from ABP_OPT, which may confer a susceptibility to neurological injury.