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Biomedical subjects

W K Morgan

Publications and source records attributed to W K Morgan.

At least 55 records · Page 3Linked to original sources
PubMed1990

Blood gas analysis as a determinant of occupationally related disability.

Arterial blood gas analysis is one of the criteria used by the Department of Labor to award total and permanent disability for coal workers' pneumoconiosis (Black Lung). We have observed that Black Lung claimants often undergo several blood gas analyses with widely differing results that sometimes range from complete normality to life-threatening hypoxemia in the same subject. We concluded that blood gas analysis in occupationally related disability determination is unreliable, in that quality control and instrumentation are variable; that severe hypoxemia is rare in coal workers' pneumoconiosis; and that such hypoxemia is nonspecific and correlates poorly with breathlessness.

Blood Gas Analysis↗
PubMed1990

Inhaled particle deposition and body habitus.

As a result of the intrapleural pressure gradient that exists in the human lung, both ventilation and particle deposition increase from apex to base. Since the intrapleural gradient varies with the height of the subject, it was decided to compare regional particle deposition in tall, short, and obese subjects to ascertain whether it was influenced by height and weight. Surprisingly, deposition in the vertical plane was not significantly influenced by the height of the subject when corrected for ventilated lung volume. In addition, it was shown that in obese subjects there was increased deposition in the middle zones relative to the apices and bases. This finding persisted after correction for ventilated lung volume and differential attenuation resulting from non-uniform thickness of the fat layer in the obese subject's chest. In the tall and short groups there was a consistent pattern in the concentric deposition of particles with there being a gradient from the central or hilar region to the periphery of the lungs, with the latter showing the most deposition.

Adipose Tissue↗
PubMed1990

Bite-to-bite variation of muscular activity in cats.

Changes in electromyographic (EMG) activity between successive bites in the jaw-closing muscles of cats are described for the reduction of food with different textures. Plots of these data suggest, and statistics confirm, that one cannot predict the magnitude of EMG activity from one bite to the next, but that predicting the direction of change in EMG activity (i.e. increases or decreases) may be possible, given the relative magnitude of a bite. The patterns observed also show that the degree of variability between masticatory cycles differs among the jaw-closing muscles and with food texture. These patterns of muscle activity are related to the neural control of jaw movements.

Animals↗
PubMed1990

The respiratory effects of cobalt.

We studied seven subjects with certain manifestations of cobalt-induced lung disease. All worked with cobalt and were involved in either the production or use of hard metal. The mode of presentation varied from an acute hypersensitivity pneumonitis that cleared completely when exposure ceased to progressive severe interstitial fibrosis of the lungs. In one subject reexposure was followed by a recurrence of the symptoms. All subjects showed restrictive ventilatory impairment and a reduction of their diffusing capacity. The radiologic appearances varied greatly. While two subjects had clear roentgenograms with small lung volumes, others had a micronodular pattern or small blotchy nodular infiltrates, and one had diffuse reticulonodulation as is seen in cryptogenic fibrosing alveolitis. The pathologic appearances varied between desquamative interstitial pneumonia and overt mural fibrosis of the alveoli. Six of the seven patients had multinucleated giant cells in their biopsy specimens or bronchoalveolar lavage fluid.

Adult↗
PubMed1989

The topography of particle deposition in the human lung.

The effect of varying particle size on the site of deposition of inhaled particles in the human lung was measured in 11 young healthy male subjects. The simultaneous inhalation of two chemically inert, radiolabelled particles, differing in size but in no other respect, controlled for all other variables including airways geometry, breathing pattern and posture. Under conditions of quiet respiration the larger particles (3.5 microns) were preferentially deposited in the upper rather than the lower zones of the lungs as compared with the smaller particles (1.1 microns). Furthermore, the penetrance of the larger particles beyond the mucociliary escalator was greater for 3.5 microns particles in all lung zones and particularly at the apex. These findings may be of significance in the pathogenesis of those diseases induced by the inhalation of particles, vapours or fumes.

Adult↗
PubMed1989

On welding, wheezing, and whimsy.

The various exposures, hazards, and diseases that may be accounted by welders are described. The hazards of welding may be subdivided conveniently into acute toxic effects, chronic toxic effects, chronic respiratory effects, and carcinogenetic effects. Each is considered in turn and their effects on morbidity and mortality are discussed. The evidence suggests that welding is not a particularly hazardous occupation provided care is taken to limit exposure to the toxic effects of any fumes that are generated. Nonetheless, the technical aspects of welding are constantly undergoing change, and continual vigilance is necessary lest a new process introduces a formerly unrecognized hazard.

Environmental Monitoring↗
PubMed1989

Clearance of inhaled particles in ankylosing spondylitis.

Patients with ankylosing spondylitis may uncommonly develop apical fibrobullous lung disease, the cause of which is unknown. It is postulated here that rigidity of the thoracic cage leads to reduced apical clearance of inhaled particles and may thereby predispose to chronic infection. Deposition and clearance of inhaled technetium-99m sulphur colloid particles were studied in eight male patients with ankylosing spondylitis who had chest wall rigidity (mean (SD) chest expansion 1.8 (1.07) cm) but normal chest radiographs. As a reference population eight healthy male volunteers were also studied. Particle deposition showed an increasing gradient from apex to base, with no significant difference between patients and controls. Clearance was assessed by comparing absolute counts, corrected for decay, at 24 hours with the baseline values. No delay in particle clearance in those with ankylosing spondylitis was apparent.

Adult↗
PubMed1988

Radiographic abnormalities and duration of employment in Western Australian iron-ore miners.

Plain chest radiographs of 788 Pilbara iron-ore miners from Western Australia have been examined by two independent observers for evidence of pneumoconiosis. The prevalence of any radiographic abnormality (a profusion grade of 0/1 or greater on the International Labour Office [ILO] scale) was 6.7% for Reader 1 and 9.9% for Reader 2. The prevalence of a definite radiographic abnormality (a profusion grade of 1/0 or greater on the ILO scale) was 1.9% for Reader 1 and 2.8% for Reader 2. The prevalence of any abnormality, as identified by either or by both observers, was significantly related to age. The relationship between a radiographic abnormality and the duration of employment was less clear. The results indicate a need for more detailed and comprehensive studies of the effects of iron-ore dust in this industry.

Adolescent↗
PubMed1988

Radiographic abnormalities in relation to total dust exposure at a bauxite refinery and alumina-based chemical products plant.

A cross-sectional study of 788 male employees of an aluminum production company examined the relationship of radiographic abnormalities to smoking and dust exposure from the mining and refining of bauxite to alumina. Among the aluminas produced were low temperature range transitional forms. The present analyses were limited to nonsmokers and current smokers. Two National Institute of Occupational Safety and Health (NIOSH)-certified "B" readers interpreted the radiographs. The predominant radiographic abnormalities noted were scanty, small, irregular opacities in the lower zones of profusion 0/1 to 1/1. Rounded opacities were rare. Among nonsmokers with low dust exposures, the prevalence of opacities greater than or equal to 1/0 showed no trend with increasing age and duration of exposure, suggesting no relationship between age and prevalence of opacities of Category 1 or more in this cohort (p greater than 0.10). Nonsmokers who had accumulated higher dust exposures showed a trend of increasing prevalence of opacities with increasing duration, suggesting an effect of occupational exposure at higher cumulative exposure levels (p less than 0.05). In most exposure categories, smokers exceeded nonsmokers in their prevalence of opacities greater than or equal to 1/0; the overall prevalence among smokers being 12 and 11% according to Readers A and B, respectively, compared with 4% in nonsmokers (p less than 0.01). In conclusion, 7 to 8% of aluminum workers in this cohort had radiographic findings of scanty, small, irregular opacities, the prevalence of which was increased among smokers (p less than 0.01). There was a moderate increase in the prevalence of opacities with increasing tenure in nonsmokers with high cumulative exposures (p less than 0.05).

Aging↗
PubMed1988

The effects of kaolin on the lung.

We studied the prevalence of ventilatory impairment, chest symptoms, and radiographic abnormality in a selected sample of more than 2,000 kaolin workers from east central Georgia. The presence of ventilatory impairment was related to the presence of complicated pneumoconiosis, employment in clay calcining, and cigarette smoking. In those working with calcined clay, there was an increased prevalence of abnormality of the FEV1, but not the FVC, when compared to both wet and dry processors and which could not be explained by either cigarette smoking or the presence of pneumoconiosis. The magnitude of abnormality in the calcined clay workers was, however, unlikely to lead to disabling impairment. In workers with more than 3-yr tenure, there were 90 subjects with simple pneumoconiosis and 18 with complicated pneumoconiosis, yielding an adjusted prevalence of 3.2% and 0.63%, respectively, in the sample examined. Dry processing was associated with a greater risk of developing pneumoconiosis than wet processing.

Adult↗
PubMed1987

The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part III. Radiographic findings.

A study was conducted to estimate the exposure-response relationship for tremolite-actinolite fiber exposure and radiographic findings among 184 men employed at a Montana vermiculite mine and mill. Workers were included if they had been employed during 1975-1982 and had achieved at least 5 years tenure at the Montana site. Past fiber exposure was associated with an increased prevalence of parenchymal and pleural radiographic abnormalities. Smoking was not significantly related to the prevalence of small opacities. However, the number of workers who had never smoked was small, and this prevented measurement of the smoking effect. Under control for smoking and age, the prevalence of small opacities was significantly greater for vermiculite workers with greater than 100 fiber/cc-years exposure than for comparison groups (cement workers, blue collar workers, and coal miners) who had no known occupational fiber exposure. A logistic model predicted an increase of 1.3% in the odds ratio for small opacities at an additional exposure of 5 fiber-years.

Adult↗
PubMed1987

Fansidar hypersensitivity pneumonitis.

We report a subject who had Fansidar prescribed to him for the purpose of malaria prophylaxis. This agent is a combination of pyrimethamine and sulphadoxine. He subsequently developed severe hypersensitivity pneumonia and required mechanical ventilation. We believe that sulphadoxine was responsible for his illness.

Alveolitis, Extrinsic Allergic↗