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Biomedical subjects

G Nyman

Publications and source records attributed to G Nyman.

At least 19 recordsLinked to original sources
PubMed1992

Distribution studies of theophylline: microdialysis in rat and horse and whole body autoradiography in rat.

After intravenous administration of theophylline, microdialysis has been used for studying the non protein bound theophylline concentration in blood and in lung tissue in the rat as well as in two horses. The distribution pattern of 14C-theophylline in the rat was also investigated. When the distribution of theophylline was completed the time course of free drug in the interstitial fluid in lung tissue was in good agreement with the total concentration-time profile in plasma in both species. In the rat the free concentration of theophylline in the lung was slightly lower than the free concentration in the blood from 40 to 300 min. The in vivo protein binding in blood was 48.8 +/- 6.2% in the rats (n = 9) and 8-25% in the horses (n = 2). The whole body autoradiography study in rat showed that the concentration of radioactivity in the lung followed the blood concentration very closely up to 24 h after injection. The effect of theophylline in the lung can be assumed to be related to the plasma concentration of theophylline, since the concentration-time profile in plasma reflects the time course in the lung.

Animals↗
PubMed1992

Green Spring criteria for medical necessity of outpatient treatment and its use in a mental health utilization review program.

The authors have developed a two-tiered method for utilization review of outpatient mental health services. The methodology looks at initial and continued treatment evaluation and uses diagnosis, symptoms, plan of treatment, and the Global Assessment Scale (GAS) among other indicators to determine appropriateness of treatment. Preliminary program experience has been positive and is included.

Ambulatory Care↗
PubMed1991

Discontinuation of neuroleptic medication in older, outpatient schizophrenics. A placebo-controlled, double-blind trial.

Thirty-five schizophrenic outpatients over the age of 52 who had been stable on neuroleptic medication were all switched to haloperidol. Ten patients were unable to tolerate the haloperidol and two dropped out of the study. The remaining 23 patients were randomly and blindly assigned to haloperidol or placebo and then followed for 6 months. Five patients did not complete the study due to medical or administrative reasons. Among the patients who completed the study, five of 10 randomized to placebo relapsed compared with only one of eight randomized to haloperidol. However, three of 10 patients randomized to placebo have remained stable without medication for 2.5 years.

Age Factors↗
PubMed1991

Pulmonary gas exchange correlated to clinical signs and lung pathology in horses with chronic bronchiolitis.

Eight horses (mean weight 438 kg) with chronic obstructive pulmonary disease (COPD) were studied for clinical signs, ventilation/perfusion relationships (VA/Q) and lung morphology. Four horses were killed and necropsied after the study. In horses with COPD, minute ventilation was almost twice as high as normal, whereas PaO2 was significantly decreased. Cardiac output was normal, but pulmonary artery pressure and pulmonary vascular resistance were significantly increased. The VA/Q distribution was abnormal with an increased scatter of VA/Q ratios. However, shunt (VA/Q = 0) was increased in one horse only. Ventilation of dead space and high VA/Q regions (VA/Q greater than 10) were increased markedly and comprised 74 per cent of minute ventilation. On lung biopsy, all horses showed chronic bronchiolitis with epithelial hyperplasia and metaplasia. Diffuse acinar hyperinflation also was evident at necropsy. There was a significant inverse correlation between the respiratory rate and the fractional ventilation of normal VA/Q regions. Also, there was a significant agreement between the extent of bronchiolar epithelial hyperplasia in necropsy specimens of lungs and the degree of ventilation of high VA/Q regions and dead space. The findings suggest that hyperinflation of the lung due to obstructed airways may be the common denominator of increased ventilation of high VA/Q regions and dead space ventilation and of elevated pulmonary artery pressure in horses with COPD from chronic bronchiolitis.

Animals↗
PubMed1991

The Maryland Plan: the rest of the story.

Since 1976 the Maryland Plan, a statewide initiative sponsored jointly by the University of Maryland and the Maryland Mental Hygiene Administration, has recruited more than 200 university-trained psychiatrists into Maryland's state hospitals and community mental health centers. Although the plan's goals and strategies have been well publicized, no comparable joint state-university recruitment program has been launched outside of Maryland. The authors describe the conditions in Maryland that made successful collaboration possible, including a large and stable university residency program, attractive incentives available for the university from the state, a favorable economic climate, a crusading spirit, and psychiatric authority in the central office of the mental hygiene administration.

Academic Medical Centers↗
PubMed1990

Atelectasis causes gas exchange impairment in the anaesthetised horse.

The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the 'normal' regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.

Anesthesia↗
PubMed1989

Ventilation-perfusion relationships in the anaesthetised horse.

Ventilation-perfusion relationships were studied by the multiple inert gas elimination technique in seven horses while they were conscious and during inhalation anaesthesia with halothane. A generally good match between ventilation and perfusion was found in the conscious, standing horse. During anaesthesia a huge shunt developed, ie perfusion of completely unventilated lung regions, both in dorsal and left lateral recumbency and whether the horse was breathing spontaneously or mechanically ventilated. The shunt was significantly greater and the arterial oxygen tension (PaO2) significantly lower in dorsal than in left lateral recumbency. Little or no perfusion of low VA/Q regions was observed during anaesthesia, whether ventilation was spontaneous or mechanical. Positive end-expiratory pressure (PEEP) did not significantly improve PaO2 or reduce the shunt. Selective mechanical ventilation of dependent lung regions with PEEP reduced the shunt markedly, an effect that was not achieved by conventional mechanical ventilation with general PEEP. The findings seem compatible with alveolar collapse during anaesthesia, causing shunt, whereas the absence of clearly low VA/Q regions questions the role of airway closure as the major disturbance of gas exchange.

Anesthesia, Inhalation↗
PubMed1988

Sampling irregularity perturbs visual reconstruction.

We explored the human observer's ability to detect and discriminate sine-wave and square-wave gratings that were sampled at intervals varying from 4.7 to 9.4 arcmin. To study the effect of sampling irregularity on visual performance, we varied the position of each line sample on the basis of a Gaussian probability distribution, the standard deviation of which varied from 0 (regular sampling) to 4.7 arcmin (highly irregular sampling). The results indicate that irregular sampling has no systematic effect on the observer's ability merely to detect the presence of a sine- or square-wave grating. In contrast, sampling irregularity strongly impairs the subject's ability to discriminate between these waveforms. A model based on the convolution of difference-of-Gaussians-type weighting profiles predicted that sampling irregularity should have little to no effect on the output of a channel tuned to the third harmonic of the square-wave grating. The findings thus suggest the existence of a sampling scheme in the visual system. This scheme is based on local feature-selective mechanisms, probably edge detectors, that are highly sensitive to the relative position of the sample points in the space domain.

Discrimination, Psychological↗