Is the Cushing mechanism a dynamic blood pressure-stabilizing system? Insights from Granger causality analysis of spontaneous blood pressure and cerebral blood flow

Saqib Saleem, Paul D. Teal, Connor A. Howe, Michael M. Tymko, Philip N. Ainslie, Yu-Chieh Tzeng
2018 American Journal of Physiology. Regulatory Integrative and Comparative Physiology  
Saleem S, Teal PD, Howe CA, Tymko MM, Ainslie PN, Tzeng YC. Is the Cushing mechanism a dynamic blood pressure-stabilizing system? Insights from Granger causality analysis of spontaneous blood pressure and cerebral blood flow. Blood pressure (BP) regulation is widely recognized as being integral to the control of end-organ perfusion, but it remains unclear whether end-organ perfusion also plays a role in driving changes in BP. A randomized and placebocontrolled study design was followed to
more » ... s followed to examine feedback relationships between very-low-frequency fluctuations in BP and cerebral blood flow (CBF) in humans under placebo treatment and ␣1-adrenergic blockade. To determine the causal relations among hemodynamic variables, BP, middle cerebral artery blood velocity (MCAv), and end-tidal CO 2 time-series were decimated, low-pass filtered (Ͻ0.07 Hz), fitted to vector autoregressive models, and tested for Granger causality in the time domain. Results showed that 1) at baseline, changes in BP and MCAv often interact in a closed-loop; and 2) ␣1-adrenergic blockade results in the dominant causal direction from BP to MCAv. These results suggest that, between subjects, cerebral pressure-flow interactions at time scales Ͻ 0.07 Hz are frequently bidirectional, and that in the presence of an intact autonomic nervous system BP may be regulated by reflex pathways sensitive to changes in CBF. blood pressure; cerebral blood flow; Cushing mechanism; Granger causality; sympathetic control
doi:10.1152/ajpregu.00032.2018 pmid:29668325 fatcat:qvytxsn63rdmhg67frdmp5qzhq