Assessment of cerebral oxygenation oscillations in subjects with hypertension

Purpose: The objective of this study was to assess the spontaneous oscillations in subjects with hypertension based on the wavelet transform of cerebral oxygenation signal measured with near-infrared spectroscopy (NIRS). Methods: Continuous recordings of NIRS and arterial blood pressure (ABP) signals were obtained from simultaneous measurements in 20 healthy subjects (age: 70.8 ± 5.2. years) and 22 subjects with hypertension (age: 72.5 ± 6.8. years). Results: Using spectral analysis based on wavelet transform, five frequency intervals were identified (I, 0.4-2Hz; II, 0.15-0.4Hz; III, 0.06-0.15Hz; IV, 0.02-0.06Hz and V, 0.005-0.02Hz). The amplitudes of δ[Hb] and δ[HbO2] in intervals I, II and III were significantly higher in hypertensive patients, who have increased mean flow velocity in middle cerebral artery (MCA), compared to that in the healthy subjects (p<0.01). The amplitudes of the ABP in frequency intervals III and V were significantly higher in hypertensive patients than in the healthy subjects (p<0.01). Conclusions: The present findings revealed that hypertension and increased mean flow velocity in MCA have significant effect on the cerebral oscillations. The higher cerebral oscillations might be related to the intracerebral atherosclerosis in response to systemic hypertension. In addition, the higher spontaneous oscillations in intervals III and V in ABP indicate a metabolic regulation and myogenic response to hypertension.