Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    A computer system for the identification of the cerebrospinal compensatory model (1990)
    Springer
    Acta neurochirurgica 105 (1990), S. 112-116 
    Details
    ISSN: 0942-0940
    Keywords: Cerebrospinal compensatory model ; computer system ; CSF infusion test ; intracranial pressure ; CSF resorption resistance ; pressure-volume index ; CSF formation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A computer system, based on IBM PC, was designed for the cerebrospinal compensatory model identification. The intracranial pressure (ICP) signal, registered during the lumbo-lumbar infusion test is analyzed by means of the spectral analysis algorithm in order to measure precisely the pulse wave amplitude. The amplitude and the mean ICP level, calculated repetetively within the period of about 8 seconds, are stored on the disk and form the basis for further model identification. Three different methods of identification were applied. They enable one to estimate the fundamental model parameters, such as: resistance to the cerebrospinal fluid resorption, pressure-volume index, baseline pressure, rate of formation of the cerebrospinal fluid. Statistical evaluation of the results of the infusion test analysis obtained by means of the system described in two groups of hydrocephalic patients (children and adults) is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01669992
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The hyperaemic response to a transient reduction in cerebral perfusion pressure (1992)
    Springer
    Acta neurochirurgica 115 (1992), S. 90-97 
    Details
    ISSN: 0942-0940
    Keywords: Cerebral perfusion pressure reduction ; hyperaemic response ; autoregulatory reserve ; mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A mathematical model of cerebral blood flow and the cerebrospinal fluid circulation is described which permits the study of phenomena caused by dynamic changes in cerebrovascular autoregulatory or cerebrospinal fluid compensatory reserves. A transient decrease in cerebral perfusion pressure was produced by carotid artery compression. Comparison of the computer simulations with clinical and experimental data, reported elsewhere, suggests that the transient hyperaemic response (THR) is proportional to the strength of the autoregulatory response. The relationships between the magnitude and time course of the THR, and the period and level of reduction in CPP were studied. This model suggests that simple clinical tests based on the examination of THR using transcranial Doppler velocity measurements are of potential value for the non-invasive assessment of the autoregulatory reserve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01406364
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Analysis of intracranial pressure waveform during infusion test (1988)
    Springer
    Acta neurochirurgica 93 (1988), S. 140-145 
    Details
    ISSN: 0942-0940
    Keywords: Hydrocephalus ; intracranial pressure ; wave-form ; infusion test ; computerized analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An analysis of intracranial pressure (ICP), based on an examination of the temporary correlation between the changes in amplitude of the pulse wave and the mean ICP level, is presented. The paper contains a discussion of the preliminary results of the method when applied to the analysis of ICP as monitored during infusion tests in a group of 24 children. Infusion of a certain volume of CSF is a good example of an uncompensated volume process, introduced externally into the intracranial space. Results allow an interpretation of the short term correlation coefficient RAP (correlation coefficient between ICP and variations of the amplitude of fundamental component of the pulse wave AMP), as a steady state index. According to this interpretation, the presented analysis enables the observation of a loss of equilibrium during the test. Other phenomena can also be observed, for instance a recovery to equilibrium after the test, nonlinearities of amplitude-pressure relationship, vasomotor reflexes etc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402897
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    CO2 cerebrovascular reactivity as a function of perfusion pressure — a modelling study (1993)
    Springer
    Acta neurochirurgica 121 (1993), S. 159-165 
    Details
    ISSN: 0942-0940
    Keywords: Cerebral blood flow ; autoregulation ; cerebral perfusion pressure ; carbon dioxide ; computer modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A mathematical model is described that demonstrated the properties of cerebral vascular resistance and compliance expressed as a function of cerebral perfusion pressure (CPP) and arterial CO2 partial pressure (PaCO2). The hypercapnic induced shift of the lower limit of autoregulation to a higher range of CPP, as shown by this model, is a useful characteristic that facilitates the differentiation between normal and impaired autoregulation described previously in experimental studies. Dynamic properties of cerebrovascular circulation derived from the relationship between pulse wave of CBF waveform and CPP have been analysed at different levels of PaCO2-phenomenon, being often described as dependence of blood flow velocity pulsatility index on the autoregulatory reserve. The model was also used to interpret interhemispheric asymmetry of CBF reactivity to changes in arterial concentration of CO2 in patients with carotid artery stenosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01809269
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Assessment of Critical Closing Pressure in the Cerebral Circulation as a Measure of Cerebrovascular Tone (1999)
    Springer
    Acta neurochirurgica 141 (1999), S. 1221-1227 
    Details
    ISSN: 0942-0940
    Keywords: Keywords: Intracranial pressure; critical closing pressure; cerebrovascular tone; experiment; animal.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary ¶ Critical closing pressure (CCP) calculated from the blood flow velocity (FV) and arterial blood pressure (ABP) waveforms has been previously reported to be useful in the assessment of the dynamics of cerebral circulation. We investigated the relationship between CCP and intracranial pressure (ICP) and cerebrovascular tone in a model of intracranial hypertension in 22 anaesthetised New Zealand White rabbits during manipulations of arterial CO2, ABP and vasodilatation caused by hypoxia. Recordings were made of FV in the basilar artery, ABP and ICP during subarachnoid infusion of saline. During infusion ICP and CCP were significantly correlated (R=0.68; p〈0.001), but the magnitude of increase in ICP and CCP during infusion were not correlated to each other. Linear regression between the difference: CCP-ICP (representing a factor due to vasogenic tone) and cerebral perfusion pressure (CPP=ABP-ICP) was highly significant (R=−0.87; p〈0.01). Generally, CCP decreased significantly (p〈0.05) with hypercarbia, arterial hypotension and after and post-hypoxia and the difference: CCP-ICP decreased consistently after each vasodilatatory manoeuvre studied.  Our data confirmed the linear relationship between CCP and ICP, and between the difference: CCP-ICP and cerebrovascular tone. However, because the magnitude of increase in ICP was not correlated to magnitude of change in CCP, CCP cannot be use for detection of increasing ICP quantitatively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007010050422
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Changes in transcranial Doppler flow velocity waveform following inhibition of nitric oxide synthesis (1997)
    Springer
    Acta neurochirurgica 139 (1997), S. 63-70 
    Details
    ISSN: 0942-0940
    Keywords: Transcranial Doppler ; cerebrocortical microcirculation ; basilar artery ; nitric oxide ; rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Background Analysis of the transcranial Doppler blood flow velocity (FV) waveform is used clinically to detect changes in cerebral haemodynamic profile. Such changes may be initiated both by alterations in microvascular resistance and in the tone of the cerebral arteries. Methods The role of endothelial mechanisms was investigated using inhibition of NO synthesis by systemic administration of NG-nitro-L-arginine methyl ester (L-NAME, 6 mg/kg) followed by simultaneous monitoring of both basilar artery FV and cerebrocortical microcirculation (laser Doppler flowmetry, LDF) in aneasthetised, ventilated rabbits over 60 minutes. Results Arterial blood pressure (AP) increased significantly (p 〈 0.01) above baseline level in the second minute following L-NAME and remained elevated until the end of experiment. Time average mean and systolic FV decreased immediately following L-NAME injection, with the statistically significant (p 〈 0.01) decrease from the third minute. Diastolic FV did not show such radical changes. LDF exhibited a slow decrease with time becoming significantly lower than baseline (p 〈 0.01) at 50 min. Conclusion A gradual decrease in cortical microcirculation preceded by a rapid reaction recorded in the TCD waveform implies that an increase in the tone of the great cerebral arteries is the predominant phenomenon seen during the acute phase of NO synthase inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01850870
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Monitoring of Intracranial Compliance: Correction for a Change in Body Position (1999)
    Springer
    Acta neurochirurgica 141 (1999), S. 31-36 
    Details
    ISSN: 0942-0940
    Keywords: Keywords: Intracranial compliance; pressure-volume-index; constant term; body position.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  The objectives of our study were 1. to investigate whether the intracranial compliance changes with body position; 2. to test if the pressure-volume index (PVI) calculation is affected by different body positions; 3. to define the optimal parameter to correct PVI for changes in body position and 4. to investigate the physiological meaning of the constant term (P0) in the model of the intracranial volume-pressure relationship. Thirteen patients were included in this study. All patients were subjected to 2 to 3 different body positions. In each position, either classic bolus injection was performed for measurement of intracranial compliance and calculation of PVI or the new Spiegelberg compliance monitor was used to calculate PVI continuously. Four different models were used for calculating the constant pressure term P0 and the P0 corrected PVI values.  Pressure volume index not corrected for the constant term P0 significantly decreased with elevating the patients head (r=0.70, p〈0.0001). In contrast, volume-pressure response and ICP pulse amplitude did not change with position. Using the constant term P0 to correct the PVI we found no changes between the different body positions. Our results suggest that during the variation in body position there is no change in intracranial compliance but a change in hydrostatic offset pressure which causes a shifting of the volume-pressure curve along the pressure axis without its shape being affected. PVI measurements should either be performed only with the patient in the 0° recumbent position or that the PVI calculation should be corrected for the hydrostatic difference between the level of the ICP transducer and the hydrostatic indifference point of the craniospinal system close to the third thoracic vertebra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007010050263
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Comparison between classic-differential and automatic shunt functioning on the basis of infusion tests (1990)
    Springer
    Acta neurochirurgica 106 (1990), S. 1-8 
    Details
    ISSN: 0942-0940
    Keywords: Hydrocephalus ; shunts ; intracranial pressure ; infusion test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Infusion tests were performed in order to examine cereospinal compensatory ability in two groups of patients with impaired compensation, subjected to shunt implantation. The functioning of the classic differential shunts was compared to the automatically (Orbis-Sigma) functioning shunts. The reference group, with intact compensatory parameters is also presented. The influence of different types of shunts on the intracranial compensation ability was compared. Automatic shunts produce less decrease in the resorption resistance of CSF in the post-shunted examination than the classic differential shunts. Classic differential shunts disturb the mono-exponential character of the pressure-volume relationship in a higher degree than automatic shunts. Shunt functioning models were proposed as well as the method of detection of eventual recovery to the normal resorption reserve. This method can be applied only to patients with automatic shunts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01809325
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Computerized infusion test compared to steady pressure constant infusion test in measurement of resistance to CSF outflow (1992)
    Springer
    Acta neurochirurgica 119 (1992), S. 12-16 
    Details
    ISSN: 0942-0940
    Keywords: CSF dynamics ; resistence to CSF outflows ; CSF infusion test ; computerized analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Resistance to cerebro-spinal fluid outflow is together with intracranial pressure the most important parameter in the investigation of patients with disturbances of CSF dynamics. The methods for determination of resistance are either unreliable or too time-consuming for routine clinical use, which has limited the popularity of this kind of measurement. In this paper a method for computerized acquisition and processing of an infusion test is described. A good correlation to a standard technique is documented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01541775
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Monitoring of cerebrospinal dynamics using continuous analysis of intracranial pressure and cerebral perfusion pressure in head injury (1994)
    Springer
    Acta neurochirurgica 126 (1994), S. 113-119 
    Details
    ISSN: 0942-0940
    Keywords: Cerebrospinal dynamics ; intracranial pressure ; cerebral perfusion pressure ; waveform analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cerebrospinal dynamics has been investigated by statistical analysis of results of computerised monitoring of 80 head injured patients admitted to the Intensive Care Unit at Pinderfields General Hospital. One minute average values of intracranial pressure (ICP), systemic arterial pressure (ABP), cerebral perfusion pressure (CPP), amplitude of the fundamental component of the intracranial pressure pulse wave and the short-term moving correlation coefficient between that amplitude and mean ICP (RAP) were recorded. It was found that reduction of CPP down to 40mmHg was more often caused by decrease in ABP than increase in ICP. Further falls in CPP below 40mmHg were caused by substantial increases in ICP above 25 mmHg. The relationship between the ICP pulse wave amplitude and CPP showed a significant gradual increase in amplitude with CPP decreasing from 75 to 30 mmHg. For CPP below 30 mmHg there is a sharp decrease in amplitude followed by a change in the coefficient RAP from positive to negative values. This was interpreted as a sign of critical disturbance in cerebral circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01476419
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...