scholarly journals Assessing Cerebral Autoregulation via Oscillatory Lower Body Negative Pressure and Projection Pursuit Regression

10.3791/51082 ◽  
2014 ◽  
Author(s):  
J. Andrew Taylor ◽  
Can Ozan Tan ◽  
J. W. Hamner
Keyword(s):  
Negative Pressure ◽  
Cerebral Autoregulation ◽  
Lower Body Negative Pressure ◽  
Projection Pursuit ◽  
Lower Body ◽  
Projection Pursuit Regression

scholarly journals Defining the characteristic relationship between arterial pressure and cerebral flow

2012 ◽  
Vol 113 (8) ◽  
pp. 1194-1200 ◽  
Author(s):  
Can Ozan Tan
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Arterial Pressure ◽  
Cerebral Autoregulation ◽  
Lower Body Negative Pressure ◽  
Pressure Fluctuations ◽  
Projection Pursuit ◽  
Projection Pursuit Regression ◽  
Cerebrovascular Events ◽  
Characteristic Relationship

Reliable assessment of cerebrovascular effectiveness in buffering against pressure fluctuations may have important implications for the timing and the outcome of therapy after adverse cerebrovascular events. Although linear approaches may indicate the presence or absence of cerebral autoregulation, they are inadequate to describe its characteristics and its effectiveness. Establishing a simple yet robust methodology to reliably measure the effectiveness of cerebral autoregulation could provide a tool to guide screening and clinical options to characterize and treat adverse cerebrovascular events associated with alterations in cerebral perfusion. To test the utility of one such methodology, an oscillatory lower body negative pressure of 30–40 mmHg was used at six frequencies from 0.03 to 0.08 Hz in 43 healthy volunteers, and the pressure-flow relation and the effectiveness of autoregulation was quantified using projection pursuit regression. Projection pursuit regression explained the majority of the relationship between pressure and cerebral blood flow fluctuations and revealed its nature consistently across individuals and across separate study days. The nature of this relationship entailed an autoregulatory region wherein slow arterial pressure fluctuations are effectively counterregulated and two passive regions wherein pressure fluctuations resulted in parallel changes in flow. The effectiveness of autoregulation was significantly reduced as pressure fluctuations became faster. These results demonstrate the characteristic relationship between arterial pressure and cerebral blood flow. Furthermore, the methodology utilized in this study provides a tool that can provide unique insight to integrated cerebrovascular control and may allow diagnosis of physiological alterations underlying impaired cerebral autoregulation.

Neurohormonal responses to oscillatory lower body negative pressure in healthy subjects

2021 ◽  
Author(s):  
Akanksha Singh ◽  
Shival Srivastav ◽  
Kavita Yadav ◽  
Dinu S. Chandran ◽  
Ashok Kumar Jaryal ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Healthy Subjects ◽  
Lower Body Negative Pressure ◽  
Lower Body

Bradykinin has no acute effect on the response of forearm blood flow to sympathetic stimulation in man

1990 ◽  
Vol 78 (4) ◽  
pp. 399-401 ◽  
Author(s):  
M. J. Cullen ◽  
J. R. Cockcroft ◽  
D. J. Webb
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Negative Pressure ◽  
Enzyme Inhibitor ◽  
Lower Body Negative Pressure ◽  
Acute Effect ◽  
Acute Administration ◽  
Lower Body ◽  
Resistance Vessels ◽  
Sympathetic Responses

1. Six healthy male subjects received 0.9% (w/v) NaCl (saline) followed by incremental doses of bradykinin (1, 3 and 10 pmol/min), via the left brachial artery. Blood flow and the response of blood flow to lower-body negative pressure were measured in both forearms during infusion of saline and each dose of bradykinin. 2. Bradykinin produced a moderate and dose-dependent increase in blood flow in the infused, but not the non-infused, forearm. Lower-body negative pressure produced an approximately 15–20% reduction in blood flow in both forearms, and this response was unaffected by local infusion of bradykinin. 3. Bradykinin, in contrast to angiotensin II, had no acute effect on peripheral sympathetic responses to lower-body negative pressure. We conclude that, in forearm resistance vessels in man, withdrawal of angiotensin II, rather than accumulation of bradykinin, is likely to account for the attenuation of peripheral sympathetic responses after acute administration of a converting-enzyme inhibitor.

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