Cerebral autoregulation assessed by near-infrared spectroscopy: validation using transcranial Doppler in patients with controlled hypertension, cognitive impairment and controls

Purpose Cerebral autoregulation (CA) aims to attenuate the effects of blood pressure variation on cerebral blood flow. This study assessed the criterion validity of CA derived from near-infrared spectroscopy (NIRS) as an alternative for Transcranial Doppler (TCD). Methods Measurements of continuous blood pressure (BP), oxygenated hemoglobin (O(2)Hb) using NIRS and cerebral blood flow velocity (CBFV) using TCD (gold standard) were performed in 82 controls, 27 patients with hypertension and 94 cognitively impaired patients during supine rest (all individuals) and repeated sit to stand transitions (cognitively impaired patients). The BP-CBFV and BP-O(2)Hb transfer function phase shifts (TF phi) were computed as CA measures. Spearman correlations (rho) and Bland Altman limits of agreement (BAloa) between NIRS- and TCD-derived CA measures were computed. BAloa separation < 50 degrees was considered a high absolute agreement. Results NIRS- and TCD-derived CA estimates were significantly correlated during supine rest (rho = 0.22-0.30, N = 111-120) and repeated sit-to-stand transitions (rho = 0.46-0.61, N = 19-32). BAloa separation ranged between 87 degrees and 112 degrees (supine rest) and 65 degrees-77 degrees (repeated sit to stand transitions). Conclusion Criterion validity of NIRS-derived CA measures allows for comparison between groups but was insufficient for clinical application in individuals.