Response of cerebral tissue oxygenation and arterial blood pressure to postural change assessed by wavelet phase coherence analysis

The article is aimed at studying the relationship between arterial blood pressure (ABP) and cerebral oxygen hemoglobin signals to the change of the posture in healthy elderly subjects using wavelet phase coherence (WPCO) analysis. ABP and HbO₂ (NIRS) signals of 35 subjects (young group: 19, Age: 24.9; elderly group: 16, Age: 68.9) were acquired from experimental apparatus with continuous recordings. We assess the phase coherence between ABP and Delta [HbO₂] using WPCO in six frequency bands. The WPCO of elderly group was significantly lower in band III (F=5.50 p=0.025) during standing posture than young group. However, during post standing posture the WPCO of elderly group was significantly higher in intervals II (F=5.25 p=0.028) and V (F=6.22 p=0.018) than young group. Different wavelet phase coherence of young group and elderly group suggests the change of cerebral autoregulation (CA) because of the effect of age. The article introduces a new way to assess the relationship between ABP and cerebral oxygen hemoglobin. It might be beneficial to identify the danger of CA.