Håkan Fridén - Academia.edu (original) (raw)

Papers by Håkan Fridén

A new method, volume accounting, for the study of CSF hydrodynamics is presented, The method is b... more A new method, volume accounting, for the study of CSF hydrodynamics is presented, The method is based on the assumption that the CSF volume is constant when the CSF pressure is constant and that to each CSF pressure level there corresponds a certain CSF volume. It is shown that the method can be used to establish the CSF volume/ pressure relationship, to estimate the parameters in pressure/flow models and to validate such models.

Springer eBooks, 1976

The adult communicating hydrocephalus syndrome has been subjected to intense scientific study all... more The adult communicating hydrocephalus syndrome has been subjected to intense scientific study all over the world since Hakim and Adams drew attention to its existence (6, 7, 1). The initial enthusiasm of excellent surgical treatment results has, however, been replaced with a more subdued optimism (2, 12). No doubt, there are patients who dramatically respond to a shunt operation, but it is also obvious that many patients, fulfilling the original diagnostic criteria, do not benefit from the operation. The terms “normal-pressure hydrocephalus” and “low-pressure hydrocephalus” have been extensively used to characterize this syndrome. Systematic studies of CSF pressure have been rare. Many clinical reports have entirely lacked information of the CSF pressure values. There are reports (13) on episodic CSF pressure increase in the patients with otherwise normal pressure, and this condition has been considered to be pathogenetic. The original concept of Hakim and Adams was that here has been, at one stage of the development of the syndrome, a period of increased CSF pressure causing a dilatation of the ventricles. When the pressure decreases again, the ventricles should remain dilated also at a lower pressure due to the law of surface tension.

The intracranial volume/pressure (V/P) relationship (1,2,4,5,6) has been studied by many investig... more The intracranial volume/pressure (V/P) relationship (1,2,4,5,6) has been studied by many investigators. Most experiments have been made on animals and very little is known about the quantitative aspects in man. The present paper deals mainly with the reference values for the different V/P variables and the deviations from normal found in some pathological states.

Springer eBooks, 1986

It is an important assumption in most studies on cerebrospinal fluid (csf) dynamics, that the pre... more It is an important assumption in most studies on cerebrospinal fluid (csf) dynamics, that the pressure in the venous sinuses (Pss) does not change when the csf pressure (Pc) changes (Davson, Hollingsworth et al. 1970; Sullivan, Miller et al. 1979). By assuming a constant Pss, the changes in csf absorption with changes in Pc can be related to the Pc change alone without reference to the pressure in the recipient vessels, Pss. If however, the Pss changes in the same direction as a change in Pc, then csf outflow resistance will be overestimated if the no-change in Pss assumption is made. If Pss changes in the opposite direction to Pc then outflow resistance will be underestimated.

Springer eBooks, 1980

A cerebrospinal fluid shunt is intended to lower the intracranial pressure. It should work in par... more A cerebrospinal fluid shunt is intended to lower the intracranial pressure. It should work in parallel with the physiological CSF outflow pathways. Very little has been done, so far, to analyze the hydrodynamics of the CSF in the individual patient, the hydrodynamics of the shunt implanted in such a patient, and the hydrodynamics of the combined patient-shunt system. This paper is part of a more extended study of shunts and deals mainly with the variability of the shunt properties.

The hydrodynamics of the cerebrospinal fluid in man. Instrumentation, computer methods, investiga... more The hydrodynamics of the cerebrospinal fluid in man. Instrumentation, computer methods, investigation procedures and physiological modelling

Springer eBooks, 1983

When using the bolus method for assessing the volume/pressure properties of the cerebrospinal flu... more When using the bolus method for assessing the volume/pressure properties of the cerebrospinal fluid space the calculations are often based on the assumption of a direct exponential relationship between volume and pressure. This implies that the rectilinear relationship between CSF pressure and elastance is assumed to pass through the origin. The present paper is aimed to test the hypothesis of s\}ch an exponential relation in normal man by studying the volume/pressure relationship by means of continuous CSF infusion over a wide range of pressures.

Projektet syftar till att ta fram ett underlag som kan ligga till grund för de val man gör som an... more Projektet syftar till att ta fram ett underlag som kan ligga till grund för de val man gör som anläggningsägare då en simhall med all kringutrustning skall utformas och byggas, i syfte att såväl byggnation som drift av badhusen ska genomföras på ett så miljö- och hälsomässigt samt ekonomiskt hållbart sätt som möjligt. De aspekter som behandlas är energianvändning, vattenrening, ventilation och innemiljö, driftsoptimering genom simulering av driften med en simuleringsmodell som har tagits fram inom ramen för projektet samt städmetoder. Den övervägande delen av befintliga badhus är utrustade med reningsanläggningar bestående av sandfilter med flockningssteg. I stort sett alla badhus använder klor för att desinficera badvattnet. I och med att problemen med bildning av desinfektionsbiprodukter uppmärksammats i en allt större utsträckning på senare tid så har kompletterande reningssteg tillförts. Membranfiltrering för rening av badvatten har länge varit en allt för energikrävande teknik ...

Projektet ”Kemikaliesmarta åtgärder i förskola” har kartlagt och bedömt förändring i förekomsten ... more Projektet ”Kemikaliesmarta åtgärder i förskola” har kartlagt och bedömt förändring i förekomsten av farliga kemikalier i förskolemiljö. Tre kemikaliesmarta tillvägagångssätt har tillämpats: nybyggnation enligt fastighetsägarens miljöstyrningsrutiner som bland annat innefattar val av byggmaterial som är godkända enlig Byggvarubedömningen, ombyggnation med tillämpning av samma rutiner samt genomförandet av kemikaliesmarta åtgärder på nivå 1 i enlighet med dokumentet Vägledning för kemikaliesmart förskola som innebär utfasning av föremål som misstänkt innehålla de farliga kemikalierna från förskolan innemiljö

Optimering av industriella processer är ett viktigt steg för kvalitetsäkring av processer och pro... more Optimering av industriella processer är ett viktigt steg för kvalitetsäkring av processer och produkter och för en effektivt resurs- och energianvändning. En väsentlig del i kvalitetsarbetet med industriella batchprocesser är att spåra och minska processvariationer. Multivariata beräkningsmetoder är ett kraftfullt verktyg för detta men kräver ett systematisk arbetssätt för insamling och granskning av information, för utformning av beräkningsrutiner och för tolkning av resultaten.” Det som skiljer batchprocesser från mera vanliga kontinuerliga processer är att loggade data från processen förändras under batchens gång. Förutom dessa tidserier finns också skalära data, dvs ingångsdata som beskriver råvaror och bakgrundstillstånd samt resultatdata t.ex. i form av kvalitetsegenskaper. Den här rapporten beskriver arbetsgången vid multivariat analys och modellering av batchprocesser i industriella sammanhang. Arbetet sker i flera steg 1 Processbeskrivning 2 Datakatalogisering 3 Datainsamli...

Recent Progress in the Study and Therapy of Brain Edema, 1984

Corticosteroids, particularly dexamethasone, have been used extensively in neurosurgical practice... more Corticosteroids, particularly dexamethasone, have been used extensively in neurosurgical practice in an attempt to reduce the brain edema which frequently accompanies intracranial pathology7,8. Where it has been possible, the pretreatment of patients before neurosurgical operations has reduced the morbidity frequently associated with some procedures13, in spite of many studies there is still little agreement on the mode of action of steroids in the prevention or resolution of brain edema6, in the present study the effect of dexamethasone on the conduction of cerebrospinal fluid (CSF) across the isolated sagittal sinus has been examined.

Acta neurochirurgica. Supplementum, 1979

Proceedings of IEEE International Conference on Control and Applications CCA-94, 1994

ABSTRACT

Advances in Soft Computing

Summary. We present a method for evaluating the discriminative power of compact feature combinati... more Summary. We present a method for evaluating the discriminative power of compact feature combinations (blocks) using the distance-based scoring measure, yielding an algorithm for selecting feature blocks that significantly contribute to the outcome variation. To estimate classification ...

Journal of the European Academy of Dermatology and Venereology, 1995

Acta Neuropathologica, 1987

Autopsied brains from 55 patients with dementia between 59-95 years of age (mean age 77.9 +/- 8.1... more Autopsied brains from 55 patients with dementia between 59-95 years of age (mean age 77.9 +/- 8.1 years) and 19 non-demented individuals between 46-91 years of age (mean age 74.3 +/- 10.5 years) were examined to establish histopathological criteria for normal ageing, primary degenerative [Alzheimer's disease (AD)/senile dementia of Alzheimer type (SDAT)] and vascular (multi-infarct) dementia (MID) disorders. Senile/neuritic plaques, neurofibrillary tangles, microscopic infarcts and perivascular serum protein deposits were quantified in the frontal lobe (Brodmann area 10) and in the hippocampus. The demented patients were classified according to the DSM-III criteria into AD/SDAT and MID. Operationally defined histopathological criteria for dementias, based on the degree/amount of the histopathological changes seen in aged non-demented patients, were postulated. The demented patients were clearly separable into three histopathological types, namely AD/SDAT, MID and AD-MID, the dementia type where both the degenerative and the vascular changes are coexistent in greater extent than are seen in the non-demented individuals. Using general clinical, gross neuroanatomical and histopathological data three separate dementia classes, namely AD/SDAT, MID and AD-MID, were visualized in two-dimensional space by multivariate data analysis. This analysis revealed that the pathology in the AD-MID patients was not merely a linear combination of the pathology in AD/SDAT and MID, indicating that AD-MID might represent a dementia type of its own. The clinical diagnosis for AD/SDAT and MID was certain in only half of the AD/SDAT and one third of the MID cases when evaluated histopathologically and by multivariate data analysis. AD/SDAT, MID and AD-MID were histopathologically diagnosed in 49%, 24% and 27%, respectively, of all the dementia cases studied. Opposite correlation between the number of tangles, plaques and the patient age in non-demented and AD/SDAT cases were observed, indicating that the pathogenesis of tangles and plaques in the two groups of patients might be different and that AD/SDAT might not be a form of an exaggerated ageing process.