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Biomedical subjects

J Risberg

Publications and source records attributed to J Risberg.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Hyperbaric oxygen therapy. Now an established treatment in Norway].

Hyperbaric oxygen therapy can be a life-saving form of treatment for certain acute medical conditions, e.g. cerebral gas embolism, clostridial infections, and smoke/carbon monoxide inhalation. It has long been used for treating decompression illness in divers. As from 1994 our hospital has been delegated the national responsibility for hyperbaric medicine in Norway. This paper describes the physiological basis, indications, and contraindications for hyperbaric oxygen treatment, and summarises hyperbaric oxygen treatment in Bergen over the last two years.

Humans↗
PubMed1995

Cerebral dysfunction in fibromyalgia: evidence from regional cerebral blood flow measurements, otoneurological tests and cerebrospinal fluid analysis.

Measurements of regional cerebral blood flow (rCBF), analysis of cerebrospinal fluid, auditory brain stem responses (ABR) and oculomotor tests were performed in 19 patients with fibromyalgia. The results from the rCBF measurements showed a normal flow level with slight but significant focal flow decreases in dorsolateral frontal cortical areas of both hemispheres. The ABR results showed signs of dysfunction at least at the brain stem level and the oculomotor tests showed high frequency of pathology. The cerebrospinal fluid analysis showed discrete changes in the cell differential count. Possible explanations for the involvement of the central nervous system in fibromyalgia are discussed.

Adult↗
PubMed1995

Effects of venous gas microemboli on pulmonary gas transfer function.

Dynamic lung volumes and flows, slope of phase III of the single breath oxygen test (delta-N2), closing volume (CV), and transfer factor for carbon monoxide (TICO) were measured before and 1 h after an air dive in a hyperbaric chamber to a pressure of 0.49 MPa for 40 min. Six divers had a bottom time of 20 min and a rate of decompression of 50 kPa x min-1, and six divers had a bottom time of 24 min and a rate of decompression of 100 kPa x min-1. Decompression stops were 5 min at 0.16 MPa and 10 min at 0.13 MPa for both groups. As control exposure they were breathing O2 at atmospheric pressure for 40 min. The dive and control exposure were done on different days within 1 wk, in random order. Doppler ultrasound monitoring for venous gas microemboli (VGM) was done during the first hour after the dive. VGM were detectable in all six divers with the fast decompression rate and in one subject with the slow rate (P < 0.01). In the subjects having VGM there was a significant reduction in TICO of -5.9 +/- 4.4% compared with -0.5 +/- 3.4% after the control exposure (P = 0.034). In the five subjects without detectable VGM, the changes in TICO were -2.8 +/- 3.7% and 0.2 +/- 3.8%, respectively. There were no significant changes in dynamic lung volumes and flows, CV, or delta-N2. A reduction in TICO may reflect effects of VGM after dives in which the effect of O2 exposure is negligible.

Adult↗
PubMed1995

Effects of gas density and ambient pressure on myocardial contractility in the rat.

BACKGROUND: Cardiac contractility and myocardial blood flow have been shown to increase when anesthetized and awake rats were exposed to normoxic 0.5 MPa ambient pressure, independent of inert gas composition. Similar changes have been demonstrated in anesthetized rats breathing a dense (relative density (RD) 5) SF6-O2 gas mixture at normobaric pressure. HYPOTHESIS: The purpose of the present study was to further explore whether cardiac contractility increases during hyperbaric exposure as a response to the elevated atmospheric pressure per se or rather as a response to increased breathing gas density. METHODS: Arterial pressure, left ventricular pressure (LVP), central venous pressure and intra-esophageal pressure were monitored in anesthetized rats during simulated dives. The rats were exposed to various gas mixtures (air, SF6-N2-O2, He-N2-O2), partial pressures of O2 (PIO2 0.02 and 0.03 MPa) ambient pressure (PTot 0.1-0.3 MPa) and gas density (RD 1-10.1). RESULTS: Cardiac contractility increased briefly by 5-10% (p < 0.05) during mild hyperoxia (PIO2 0.03 MPa). A concomitant stepwise increase in RD (1-10.1) and PTot (0.1-0.3 MPa) by adding SF6 to air, increased maximal rate of LVP rise (+dP/dt) and fall (-dP/dt) by 30% (p < 0.01). Two groups of rats exposed to either a high density SF6-N2-O2 (RD 5.5) or a normal density He-N2-O2 (RD 1.2) breathing gas of identical PTot 0.2 MPa demonstrated similar rise in dP/dt (peak 72%, p < 0.05). CONCLUSION: At moderately increased ambient pressure, pressure per se increases cardiac contractility independently of the breathing gas density.

Animals↗
PubMed1994

Cortical activation during visual spatial processing: relation between hemispheric asymmetry of blood flow and performance.

Regional cerebral blood flow was studied in normal males and females during rest and three spatial tasks: counting of rectangular shapes, mental rotation, and cube analysis. Whereas gender caused no significant differences in performance scores or asymmetries, a highly significant relation was found between performance on the cube analysis task and right > left hemisphere flow asymmetry in the parietotemporooccipital border zone (PTO region) during cube analysis. This indicates that subjects utilizing a right hemisphere strategy when solving certain spatial tasks are superior to subjects with more bilateral involvement.

Adult↗
PubMed1994

Regional cerebral blood flow in sign language users.

Cerebral activation was compared during sign and spoken language comprehension. Nine hearing children of deaf parents were studied and the cerebral activation was measured by recordings of the regional cerebral blood flow. Comprehension of a complex material gave a bilateral activation of posterior temporal regions for both spoken and signed language. It seems that sign language activates the cortex in a way which is very similar to spoken language, when the listener watches the speaker. Cortical areas usually regarded to be important for spatial ability do not show enhanced activation during sign language perception.

Adult↗
PubMed1994

Ethanol reduces asymmetry of visual rCBF responses.

Visual regional CBF (rCBF) responses were measured in 10 healthy male subjects before and after an ethanol dose of 1 g/kg body weight. This dose induces well-established cerebral vasodilatation. However, significant bilateral occipital increases were found in both conditions. Apparently, the coupling between neuronal activity and rCBF is preserved following ethanol. The occipital and posterior parietal flow increases were, however, larger on the right than the left side in the sober state. During inebriation the asymmetry disappeared, possibly representing a more undifferentiated processing of visual information. We propose that ethanol causes a reduced inhibition of the left posterior cortex and a reduction of right-hemisphere information processing.

Adult↗
PubMed1994

Effect of beta 1-adrenoceptor blockade in rats at 5 bar ambient pressure.

Conscious rats exposed to 5 bar (500 kPa) ambient pressure show increased total myocardial blood flow (TMBF) and enhanced cardiac contractility in spite of unaltered mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO). Four groups of awake, adapted rats were given injections of atenolol at 1 bar air or 5 bar normoxic N2, or both. Atenolol injected at 1 bar caused a marked reduction of HR, MAP, peak left ventricular pressure (LVP), and rate of LVP rise (+dP/dt) and fall (-dP/dt). In spite of beta 1-adrenoceptor blockade, ambient pressure rise increased HR, LVP, +dP/dt, -dP/dt, TMBF, and calculated cardiac O2 consumption (P < 0.05). A second atenolol injection at 5 bar caused a brief reduction in HR but did not affect cardiac contractility. Rats receiving the first atenolol injection at 5 bar demonstrated unchanged TMBF. We conclude that beta 1-adrenoceptor blockade does not annual the increase in cardiac contractility associated with hyperbaria.

Animals↗
PubMed1993

Acute effects of alcohol on regional cerebral blood flow in man.

Acute effects of alcohol in a low (0.7 g/kg) and a high dose (1.5 g/kg) on regional cerebral blood flow (rCBF) were measured with 133Xe inhalation technique at resting conditions in 13 normals. Mean hemisphere CBF increased globally by 12% at the lower dose and 16% at the higher dose. A normal hyperfrontal flow pattern was seen in both alcohol conditions. There were, however, significant regional differences in response to alcohol. The largest rCBF increase was observed in prefrontal regions at the lower dose, and in temporal regions at the higher. Expressed in relative values (% of the whole brain CBF), the temporal rCBF increased linearly with increasing alcohol dosage, while the prefrontal rCBF showed a increase at the lower dose followed by a decrease at the higher dose. It is concluded that alcohol has two types of acute effects on rCBF, a global vasodilatory effect and some regional effects, most clearly seen in prefrontal and temporal regions. The prefrontal flow augmentation following acute alcohol intake may be related to a transient arousal reaction, which has been reported by others. The temporal flow increase may be related to effects of alcohol on emotions and mood.

Adult↗
PubMed1992

Organ blood flow and cardiac contractility in anaesthetized cats at 5 bar (500 kPa) ambient pressure.

Previous in vivo and in vitro experiments have demonstrated increased cardiac contractility and increased total myocardial blood flow (Qmyocardial) when rats were exposed to normoxic 5-bar (500 kPa) ambient pressure. In the present study, regional blood flow was measured using the microsphere method on nine anaesthetized cats at surface and normoxic 5-bar (500 kPa) ambient pressure. Left ventricular pressure (LVP) and cardiac contractility, measured as peak left ventricular +dP/dt and -dP/dt were measured in six of the cats. Arterial pressure, heart rate and cardiac output remained unchanged after compression, but total Qmyocardial increased by 29% (P less than 0.01) and cerebral blood flow increased by 66% (P less than 0.05). At the same time +dP/dt and -dP/dt was increased by 83% and 102%, respectively (P less than 0.01), while LVP was enhanced by 14% (P less than 0.05). Except for a moderate decrease in partial pressure of oxygen, acid base status in arterial blood remained unchanged. The results indicate that the effects of increased ambient pressure on the heart are general physiological phenomena, which are not only limited to the laboratory rat.

Acid-Base Equilibrium↗
PubMed1992

Redistribution of blood flow in the cerebral cortex of normal subjects during head-up postural change.

Regional cerebral blood flow was measured in 21 normotensive subjects during supine rest and during head-up tilt to 70 degrees. The results showed significant and consistent regional cerebral blood flow changes in the frontal areas with lower relative flow distribution values (percentage of mean flow) during head-up tilt than during supine rest. The lower frontal flow distribution values during tilt were not related to habituation, to repeated measurements, or to the estimated level of arterial CO2 which was derived from expired end-tidal CO2 levels. None of the subjects had orthostatic hypotension and there was no significant difference in mean hemispheric blood flow between lying down and standing up. There was no significant gender difference in regional cerebral blood flow, although female subjects tended to have higher mean hemispheric flow than males in both postures. It remains to be established whether the flow decreases in the frontal cortex are caused by cerebral functional factors or by haemodynamic mechanisms.

Adult↗
PubMed1992

Cycloid psychosis: regional cerebral blood flow correlates of a psychotic episode.

Eight patients meeting Leonhard's criteria for cycloid psychosis were investigated on repeated occasions during a psychotic episode, with regional cerebral blood flow measurements and clinical ratings. The results showed that, at admission to the hospital, when the patients were clinically exacerbated, the mean hemispheric blood flow was significantly elevated compared with values from a normal control group. The hemispheric blood flow level covaried significantly with the degree of clinical symptoms, such that the more elevated the cortical blood flow was, the more behaviorally disturbed was the patient. At discharge from the hospital, the patients had no residual symptoms and the cortical blood flow was normal. These findings differ distinctly from those commonly made in other psychoses, such as schizophrenia.

Adult↗
PubMed1991

Regional cerebral blood flow asymmetries in a group of 189 normal subjects at rest.

Regional cerebral blood flow (rCBF) asymmetries were studied in 189 subjects (96 males and 93 females) at rest with the 133Xenon inhalation method using a fixed detector system. rCBF asymmetries in the resting condition were very small, nevertheless a significant (p less than 0.001) effect for their topographical distribution was present, reflecting higher rCBF in the right fronto-temporal and left parieto-occipital regions. rCBF asymmetries were not correlated with age, and there were no significant differences between males and females. Asymmetries are therefore useful from a statistical point of view in detecting rCBF abnormalities in the resting condition: they are more stable than absolute values in normal subjects and no matching according to age or sex is required when statistical comparisons are performed.

Adolescent↗
PubMed1991

Aspects of stability of regional cerebral blood flow in chronic schizophrenia: an 18-year followup study.

Regional cerebral blood flow (rCBF) measurements and psychiatric ratings were performed on seven schizophrenic patients (mean age = 41.4 years) who had been examined 18 years previously in a study that used similar psychiatric ratings and a comparable rCBF technique. Neither the clinical symptomatology nor the rCBF level and distribution had changed appreciably between 1972 and 1990. The findings indicate that cerebral functional activity in chronic schizophrenia remains constant in spite of continuous neuroleptic medication.

Adult↗
PubMed1990

Regional cerebral blood flow in schizophrenia: repeated studies during a psychotic episode.

Regional cerebral blood flow (rCBF) measurements and clinical ratings were performed on 17 schizophrenic patients and a subgroup of 10 medication-free patients before and after treatment. While clinically exacerbated patients had normal blood flow, patients in remission showed a redistribution of flow with lower values in frontal areas. Anteroposterior ratios correlated with the degree of behavioral disturbances, suggesting that the level of frontal lobe activity in schizophrenia may be a function of the patient's clinical state at the time of study.

Adult↗
PubMed1990

Distribution of cardiac output in awake rats during exposure to 5 bar.

Previous studies have reported increased total myocardial blood flow (TMBF) after 15 min stable pressure in a normoxic O2-N2 and O2-He at 5 bar, although cardiac output (CO), heart rate (HR), and mean arterial pressure (MAP) remained unchanged. In the present study, 2 groups of awake rats were exposed to normoxic 5 bar atmospheres; group 1 breathing a He-O2-N2 mixture and group 2 a O2-N2 mixture. Organ blood flow was determined by the microsphere method in control (C) (group 1) and after 15 (T1) and 75 min (T2) hyperbaric exposures (groups 1 and 2). MAP and HR remained at control levels in group 2 animals and increased slightly (6-10%, P less than 0.05) in group 1 rats. CO remained unchanged during the experimental period in both groups. In group 1, TMBF had increased by 13% (P less than 0.05) at T1 and continued to increase at T2 for both groups. Blood flow to the liver and spleen increased during the exposure in both groups. Renal blood flow fell by 25% from C to T2 (P less than 0.05). The arterial blood gases and pH remained at the predive control level in group 2 rats, whereas serum corticosterone concentration fell to 60% during compression (P less than 0.01), possibly due to N2 narcosis, but increased gradually toward 80% of C value during the pressure exposure. We conclude that the increase in TMBF, which is initiated by compression to a 5-bar normoxic atmosphere, persists when stable pressure is maintained.

Animals↗