Intracranial pressure waves: characterization of a pulsation absorber with notch filter properties using systems analysis

2008 ◽  
Vol 2 (1) ◽  
pp. 83-94 ◽  
Author(s):  
Rui Zou ◽  
Eun-Hyoung Park ◽  
Erin McCormack Kelly ◽  
Michael Egnor ◽  
Mark E. Wagshul ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Cerebrospinal Fluid ◽  
Intracranial Pressure ◽  
Transfer Function ◽  
Input Signal ◽  
Systems Analysis ◽  
Notch Filter ◽  
Time Varying ◽  
Cardiac Frequency ◽  
Arterial Blood

Object The relationship between the waveform of intracranial pressure (ICP) and arterial blood pressure can be quantitatively characterized using a newly developed technique in systems analysis, the time-varying transfer function. This technique considers the arterial blood pressure as an input signal composed of multiple frequencies represented in the output ICP according to the transfer function imposed by the intracranial system on the input signal. The transfer function can change with time and with physiological manipulations. The authors examined data obtained from canine experiments involving manipulations of ICP. Methods The authors analyzed 11 experiments from 3 normal mongrel dogs under conditions of normal ICP and with changes in ICP made by bolus injection, infusion, or withdrawal of cerebrospinal fluid by using time-varying transfer function. Results During normal ICP periods, the gain of the transfer function displayed a deep notch (≥ 1 log unit) centered at or near the cardiac frequency. In systems terms, the intracranial compartment under normal conditions appears to act as a notch filter attenuating the cardiac frequency input relative to other frequencies. Epochs of ICP elevation showed suppression of the notch, and the notch was restored when ICP returned to normal. Conclusions The intracranial system in these animals could be considered to include a pulsation absorber for which the target frequency appears to be close to the cardiac frequency. One possible source for such an absorber mechanism might be the free movement of cerebrospinal fluid, implying that impairment of this motion may have important clinical implications in various neurological conditions such as hydrocephalus.

Resonant and notch behavior in intracranial pressure dynamics

2009 ◽  
Vol 3 (5) ◽  
pp. 354-364 ◽  
Author(s):  
Mark E. Wagshul ◽  
Erin J. Kelly ◽  
Hui Jing Yu ◽  
Barbara Garlick ◽  
Tom Zimmerman ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Intracranial Pressure ◽  
Transfer Function ◽  
Arterial Blood Pressure ◽  
Pulse Pressure ◽  
Function Analysis ◽  
Isotonic Saline ◽  
Pressure Amplitude ◽  
Arterial Blood ◽  
Transfer Function Analysis

Object The intracranial pulse pressure is often increased when neuropathology is present, particularly in cases of increased intracranial pressure (ICP) such as occurs in hydrocephalus. This pulse pressure is assumed to originate from arterial blood pressure oscillations entering the cranium; the fact that there is a coupling between the arterial blood pressure and the ICP is undisputed. In this study, the nature of this coupling and how it changes under conditions of increased ICP are investigated. Methods In 12 normal dogs, intracarotid and parenchymal pulse pressure were measured and their coupling was characterized using amplitude and phase transfer function analysis. Mean intracranial ICP was manipulated via infusions of isotonic saline into the spinal subarachnoid space, and changes in transfer function were monitored. Results Under normal conditions, the ICP wave led the arterial wave, and there was a minimum in the pulse pressure amplitude near the frequency of the heart rate. Under conditions of decreased intracranial compliance, the ICP wave began to lag behind the arterial wave and increased significantly in amplitude. Most interestingly, in many animals the pulse pressure exhibited a minimum in amplitude at a mean pressure that coincided with the transition from a leading to lagging ICP wave. Conclusions This transfer function behavior is characteristic of a resonant notch system. This may represent a component of the intracranial Windkessel mechanism, which protects the microvasculature from arterial pulsatility. The impairment of this resonant notch system may play a role in the altered pulse pressure in conditions such as hydrocephalus and traumatic brain swelling. New models of intracranial dynamics are needed for understanding the frequency-sensitive behavior elucidated in these studies and could open a path for development of new therapies that are geared toward addressing the pulsation dysfunction in pathological conditions, such as hydrocephalus and traumatic brain injury, affecting ICP and flow dynamics.

scholarly journals Quantifying the contribution of intracranial pressure and arterial blood pressure to spontaneous tympanic membrane displacement

2018 ◽  
Vol 39 (8) ◽  
pp. 085002
Author(s):  
Wahbi K El-Bouri ◽  
Dario Vignali ◽  
Konstantina Iliadi ◽  
Diederik Bulters ◽  
Robert J Marchbanks ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Intracranial Pressure ◽  
Tympanic Membrane ◽  
Arterial Blood Pressure ◽  
Arterial Blood ◽  
Membrane Displacement

The relationship of blood flow velocity fluctuations to intracranial pressure B waves

1992 ◽  
Vol 76 (3) ◽  
pp. 415-421 ◽  
Author(s):  
David W. Newell ◽  
Rune Aaslid ◽  
Renate Stooss ◽  
Hans J. Reulen
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Intracranial Pressure ◽  
Arterial Blood Pressure ◽  
Wave Amplitude ◽  
Transcranial Doppler Ultrasound ◽  
Normal Subjects ◽  
Content Type ◽  
Arterial Blood ◽  
Flow Fluctuations

✓ Intracranial pressure (ICP) and continuous transcranial Doppler ultrasound signals were monitored in 20 head-injured patients and simultaneous synchronous fluctuations of middle cerebral artery (MCA) velocity and B waves of the ICP were observed. Continuous simultaneous monitoring of MCA velocity, ICP, arterial blood pressure, and expired CO2 revealed that both velocity waves and B waves occurred despite a constant CO2 concentration in ventilated patients and were usually not accompanied by fluctuations in the arterial blood pressure. Additional recordings from the extracranial carotid artery during the ICP B waves revealed similar synchronous fluctuations in the velocity of this artery, strongly supporting the hypothesis that blood flow fluctuations produce the velocity waves. The ratio between ICP wave amplitude and velocity wave amplitude was highly correlated to the ICP (r = 0.81, p < 0.001). Velocity waves of similar characteristics and frequency, but usually of shorter duration, were observed in seven of 10 normal subjects in whom MCA velocity was recorded for 1 hour. The findings in this report strongly suggest that B waves in the ICP are a secondary effect of vasomotor waves, producing cerebral blood flow fluctuations that become amplified in the ICP tracing, in states of reduced intracranial compliance.

Suctioning and Cerebral Blood Flow

PEDIATRICS ◽  
1984 ◽  
Vol 73 (5) ◽  
pp. 737-737
Author(s):  
JEFFREY M. PERLMAN ◽  
JOSEPH J. VOLPE
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Intracranial Pressure ◽  
Flow Velocity ◽  
Arterial Blood Pressure ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Base Line ◽  
Arterial Blood

In Reply.— Marshall misread a critical piece of information in the text. His interpretation of the data would be correct, if the intracranial pressure, arterial blood pressure, and cerebral blood flow velocity changes occurred simultaneously. However, as we stated in the text (see section on "Temporal Features of Changes with Suctioning"), the intracranial pressure fell to base-line values immediately following suctioning, whereas the changes in arterial blood pressure and cerebral blood flow velocity occurred more slowly over an approximately two-minute period.

Energy Harvesting From Arterial Blood Pressure for Embedded Brain Sensing

2016 ◽  
Author(s):  
Aditya Nanda ◽  
M. Amin Karami
Keyword(s):  
Blood Pressure ◽  
Transfer Function ◽  
Arterial Blood Pressure ◽  
Radial Pressure ◽  
Radial Breathing Mode ◽  
Curved Beam ◽  
Induced Voltage ◽  
Governing Equations ◽  
Arterial Blood ◽  
Straight Beam

This paper investigates energy harvesting from arterial blood pressure via the piezoelectric effect for the purpose of powering embedded micro-sensors in the brain. Blood flow is highly dynamic and arterial blood pressure varies, in the average human blood vessel, from 120 mm of Hg to 80 mm of Hg and we look at transduction of this pressure variation to electric energy via the piezoelectric effect. We propose two different geometries for this purpose. Initially, we look at the energy harvested by a cylinder, coated with PVDF (Polyvinylidene fluoride) patches, placed inside an artery acted upon by blood pressure. The arrangement is similar to that of a stent which is a cylinder placed in veins and arteries to prevent obstruction in blood flow. The governing equations of the harvester are obtained using Hamilton’s principle. Pressure acting in arteries is radially directed and this is used to simplify the governing equations. Specifically, radial pressure directed on the inner wall of the cylinder is assumed to excite only the radial breathing mode of vibration. Using this, the transfer function relating pressure to the induced voltage across the surface of the harvester is derived and the power harvested by the cylindrical harvester is obtained for different shunt resistances. However, the natural frequency of the radial breathing mode (RBM) is found to be very high and the harvested power at the frequencies of interest (3 Hz – 20 Hz) is very low. To decrease the natural frequency, we propose a novel streaked cylinder design that involves cutting the cylinder along the length, transforming it to a curved beam with an opening angle of 360 deg.. The governing equations corresponding to a circular curved beam, with PVDF patches on top and bottom surfaces, are derived using Hamilton’s principle and modal analysis is used to obtain the transfer function relating radial pressure to induced voltage. We validate the derived transfer function by evaluating the harvested power for a beam with very large radius of curvature; in which case, the curved beam becomes a straight beam and the harvested power is compared with the same for a straight beam (which exists in the literature). Further, we conduct design analyses and obtain the power as the geometric parameters of the harvester are varied for the purpose of optimizing the dimensions of harvester for maximal power generation. The power harvested by the harvester, at lower frequencies is deemed to be satisfactory.

Sevoflurane Increases Lumbar Cerebrospinal Fluid Pressure in Normocapnic Patients Undergoing Transsphenoidal Hypophysectomy 

1999 ◽  
Vol 91 (1) ◽  
pp. 127-130 ◽  
Author(s):  
Pekka Talke ◽  
James E. Caldwell ◽  
Charles A. Richardson
Keyword(s):  
Blood Pressure ◽  
Cerebrospinal Fluid ◽  
Intracranial Pressure ◽  
Systolic Blood Pressure ◽  
Cerebral Perfusion Pressure ◽  
Cerebral Perfusion ◽  
Perfusion Pressure ◽  
Csf Pressure ◽  
Sevoflurane Group ◽  
Lumbar Cerebrospinal Fluid

Background The data on the effect of sevoflurane on intracranial pressure in humans are still limited and inconclusive. The authors hypothesized that sevoflurane would increase intracranial pressure as compared to propofoL METHODS: In 20 patients with no evidence of mass effect undergoing transsphenoidal hypophysectomy, anesthesia was induced with intravenous fentanyl and propofol and maintained with 70% nitrous oxide in oxygen and a continuous propofol infusion, 100 microg x kg(-1) x min(-1). The authors assigned patients to two groups randomized to receive only continued propofol infusion (n = 10) or sevoflurane (n = 10) for 20 min. During the 20-min study period, each patient in the sevoflurane group received, in random order, two concentrations (0.5 times the minimum alveolar concentration [MAC] and 1.0 MAC end-tidal) of sevoflurane for 10 min each. The authors continuously monitored lumbar cerebrospinal fluid (CSF) pressure, blood pressure, heart rate, and anesthetic concentrations. Results Lumbar CSF pressure increased by 2+/-2 mmHg (mean+/-SD) with both 0.5 MAC and 1 MAC of sevoflurane. Cerebral perfusion pressure decreased by 11+/-5 mmHg with 0.5 MAC and by 15+/-4 mmHg with 1.0 MAC of sevoflurane. Systolic blood pressure decreased with both concentrations of sevoflurane. To maintain blood pressure within predetermined limits (within+/-20% of baseline value), phenylephrine was administered to 5 of 10 patients in the sevoflurane group (range = 50-300 microg) and no patients in the propofol group. Lumbar CSF pressure, cerebral perfusion pressure, and systolic blood pressure did not change in the propofol group. Conclusions Sevoflurane, at 0.5 and 1.0 MAC, increases lumbar CSF pressure. The changes produced by 1.0 MAC sevoflurane did not differ from those observed in a previous study with 1.0 MAC isoflurane or desflurane.

The effect of nimodipine on intracranial pressure

1987 ◽  
Vol 67 (3) ◽  
pp. 387-393 ◽  
Author(s):  
Mark N. Hadley ◽  
Robert F. Spetzler ◽  
Mary S. Fifield ◽  
William D. Bichard ◽  
John A. Hodak
Keyword(s):  
Blood Pressure ◽  
Intracranial Pressure ◽  
Systemic Blood Pressure ◽  
Artery Occlusion ◽  
Content Type ◽  
Arterial Blood ◽  
Increased Risk ◽  
Before And After ◽  
The Right ◽  
Cerebral Artery Occlusion

✓ Nimodipine was administered by intravenous infusion to six male baboons before, during, and after 6 hours of middle cerebral artery occlusion. Intracranial pressure (ICP) and systemic blood pressure were monitored continuously. An epidural balloon was inflated at regular intervals at three levels of arterial CO2 tension (25, 35, and 50 mm Hg) before and after the administration of nimodipine, and volume-pressure curves were generated. In every case, curves generated after intravenous nimodipine infusion were lower and shifted more to the right than the same set of curves generated before nimodipine administration, regardless of the baseline ICP. The reduction in ICP following nimodipine infusion was not due to a reduction in mean arterial blood pressure and was statistically significant at all three levels of pCO2 (p < 0.01). These results suggest that, in the presence of elevated ICP due to cerebral infarction, there is no increased risk of exacerbating intracranial hypertension with the addition of nimodipine.

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