Cerebral blood flow velocity response to induced and spontaneous sudden changes in arterial blood pressure

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 280; no. 5; pp. H2162 - H2174
• Main Authors: Panerai, Ronney B, Dawson, Suzanne L, Eames, Penelope J, Potter, John F
• Format: Journal Article
• Language: English
• Published: United States 01.05.2001
• Subjects: Adult; Aged; Aged, 80 and over; Blood Flow Velocity - physiology; Blood Pressure - physiology; Cerebrovascular Circulation - physiology; Cold Temperature; Female; Hand Strength - physiology; Homeostasis - physiology; Humans; Lower Body Negative Pressure; Male; Middle Aged; Thigh; Valsalva Maneuver - physiology; Vascular Resistance - physiology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.280.5.h2162

Division of Medical Physics, University of Leicester, Leicester Royal Infirmary, Leicester LE1 5WW; and Division of Medicine for the Elderly, University of Leicester, Glenfield Hospital, Leicester LE3 9QP, United Kingdom The influence of different types of maneuvers that can induce sudden changes of arterial blood pressure (ABP) on the cerebral blood flow velocity (CBFV) response was studied in 56 normal subjects (mean age 62 yr, range 23-80). ABP was recorded in the finger with a Finapres device, and bilateral recordings of CBFV were performed with Doppler ultrasound of the middle cerebral arteries. Recordings were performed at rest (baseline) and during the thigh cuff test, lower body negative pressure, cold pressor test, hand grip, and Valsalva maneuver. From baseline recordings, positive and negative spontaneous transients were also selected. Stability of P CO 2 was monitored with transcutaneous measurements. Dynamic autoregulatory index (ARI), impulse, and step responses were obtained for 1-min segments of data for the eight conditions by fitting a mathematical model to the ABP-CBFV baseline and transient data (Aaslid's model) and by the Wiener-Laguerre moving-average method. Impulse responses were similar for the right- and left-side recordings, and their temporal pattern was not influenced by type of maneuver. Step responses showed a sudden rise at time 0  and then started to fall back to their original level, indicating an active autoregulation. ARI was also independent of the type of maneuver, giving an overall mean of 4.7 ± 2.9 ( n  = 602 recordings). Amplitudes of the impulse and step responses, however, were significantly influenced by type of maneuver and were highly correlated with the resistance-area product before the sudden change in ABP ( r  =  0.93, P  < 0.0004). These results suggest that amplitude of the CBFV step response is sensitive to the point of operation of the instantaneous ABP-CBFV relationship, which can be shifted by different maneuvers. Various degrees of sympathetic nervous system activation resulting from different ABP-stimulating maneuvers were not reflected by CBFV dynamic autoregulatory responses within the physiological range of ABP. cerebral circulation; cerebrovascular resistance; cerebral autoregulation; thigh cuff test; cold pressor test; hand grip; Valsalva maneuver