Search PubMed⌕ Search

Biomedical subjects

N W White

Publications and source records attributed to N W White.

At least 19 recordsLinked to original sources
PubMed1998

Prevalence of occupational lung disease in a random sample of former mineworkers, Libode District, Eastern Cape Province, South Africa.

BACKGROUND: Gold mineworkers in South Africa are exposed to high levels of silica dust as a result of which they are at risk of developing silicosis, which is a compensable disease. The incidence of tuberculosis is also high. METHODS: To determine the prevalence of occupational lung disease and the previous compensation history in former migrant mineworkers, a study was undertaken in a random sample of men living in Libode, a rural district of Eastern Cape Province, South Africa. Two hundred thirty-eight ex-mineworkers were examined according to a protocol that included chest radiography and spirometry. Chest radiographs were read into the International Labour Organisation (ILO) classification for pneumoconioses by two readers. RESULTS: The mean age was 52.8 years, and the mean length of service was 12.15 years. The prevalence of pneumoconiosis (> or = ILO 1/0) was 22% and 36% (variation by reader). For both readers, a significant association between length of service and pneumoconiosis and between pneumoconiosis and reduction in FVC and FEV was found. Twenty-four percent of study subjects were eligible for compensation. CONCLUSION: There is a high prevalence of previously undiagnosed, uncompensated pneumoconiosis in the study group. As a result of the failure to diagnose and compensate occupational lung disease, the social and economic burden of such disease is being borne by individuals, households, and the migrant labor-sending communities as a whole.

Adult↗
PubMed1997

Prevalence of occupational lung disease among Botswana men formerly employed in the South African mining industry.

OBJECTIVE: To determine whether previous health experiences affect the prevalence of occupational lung disease in a semirural Botswanan community where there is a long history of labour recruitment to South African mines. METHOD: A cross sectional prevalence study of 304 former miners examined according to a protocol including a questionnaire, chest radiograph, spirometry, and medical examination. RESULTS: Overall mean age was 56.7 (range 28-93) years, mean duration of service 15.5 (range 2-42) years. 26.6% had a history of tuberculosis. 23.3% had experienced a disabling occupational injury. Overall prevalence of pnemoconiosis (> 1/0 profusion, by the International Labour Organisation classification) was 26.6%-31.0%, and 6.8% had progressive massive fibrosis (PMF). Many were entitled to compensation under South African law. Both radiograph readers detected time response relations between pneumoconiosis and PMF among the 234 underground gold miners. PMF could result from < 5 years of exposure, but was not found < 15 years after first exposure. Both pulmonary tuberculosis (PTB) and pneumoconiosis were found to be associated with airflow limitation. CONCLUSIONS: Former miners in Botswana have a high prevalence of previously unrecognised pneumoconiosis, indicative of high previous exposures to fibrogenic respirable dust. Their pneumoconiosis went unrecognised because they had no access to surveillance after employment. Inadequate radiographic surveillance or failure to act on results when employed or when leaving employment at the mines could have contributed to under recognition. Community based studies of former miners are essential to fully evaluate the effects of mining exposures. Our findings indicate a failure of established measures to prevent or identify pneumoconiosis while these miners were in employment and show that few of the social costs of occupational lung diseases are borne by mining companies through the compensation system.

Accidents, Occupational↗
PubMed1997

Regression of polyvinylchloride polymer pneumoconiosis.

A 35 year old man heavily exposed to polyvinylchloride (PVC) polymer dust developed dyspnoea and a mild restrictive lung disorder consistent with PVC pneumoconiosis. Clinical and radiological abnormalities cleared on removal from exposure, suggesting that in its early stages PVC pneumoconiosis is reversible.

Adult↗
PubMed1996

Acute-phase response and the hypercoagulable state in pulmonary tuberculosis.

In our experience, severe pulmonary tuberculosis (PTB) is often complicated by deep venous thrombosis (DVT). Because of the association between inflammation and haemostatic changes that can result in a hypercoagulable state, we have prospectively examined such predisposing factors in representative patients. Sequential analyses in a control group with active PTB showed anaemia, thrombocytosis, elevations in plasma fibrinogen, fibrin(ogen) degradation products (FDP), tissue plasminogen activator (t-PA) and inhibitor (PAI-1) with depressed antithrombin III levels. Age, sex and disease matched individuals with venographically proven DVT had higher FDP (15.8 +/- 14.3 v 3.2 +/- 1.7 micrograms/ml:P < 0.01), t-PA (19.4 +/- 14.9 v 11.3 +/- 0.8 ng/ml:P < 0.01), and functional PAI-1 activity (11.6 +/- 6.3 v 4.2 +/- 4.1:P < 0.01) with lower platelet counts (347 +/- 110 v 563 +/- 230 x 10(9)/1:P < 0.01). Fibrinogen levels in all patients rose during the first 2 weeks of therapy and, together with related disturbances, corrected within 12 weeks. In conclusion, elevated plasma fibrinogen with impaired fibrinolysis coupled with a decrease in antithrombin III and reactive thrombocytosis would appear to favour the development of DVT in PTB.

Acute-Phase Reaction↗
PubMed1994

Review and analysis of variation between spirometric values reported in 29 studies of healthy African adults.

Within- and between-population variation in spirometric measurements has been addressed in a systematic review of spirometric measurements from 29 studies published between 1965 and 1990 involving 9,690 men and 2,638 women of sub-Saharan African ancestry; FVC and FEV1 were age- and height-standardized at BTPS. Between- population differences were related to geographic region and sample source (workforce versus community). The effects of altitude, variation in sample mean height, and year of study publication were also significant variables in multivariate models explaining between-population differences. Altitude was the most important variable with an effect of 263 ml/1,000 m (95% confidence interval [CI] 120-410) on FVC in men. In women, variation in sample mean height was also important, with taller populations having larger values for FVC (64 ml/cm). In men, secular trends were evident, with date of study associated with negative trends among men in the U.S.A. (-35.3 ml/year), and positive trends (14.7 ml/year) in other regions. These differences in trend could not be explained. Population selection factors, altitude, date of study, and other biological sources of variation need to be taken into account in evaluating between- and within-population comparisons of spirometric measurements.

Adult↗
PubMed1992

Workmens' compensation and byssinosis in South Africa: a review of 32 cases.

Byssinosis has been compensable in the Republic of South Africa (RSA) since 1973. The legal and administrative provisions for byssinosis compensation are reviewed. A series of 32 cases of presumed byssinosis was submitted to the compensation authorities by the authors. Identical reports were submitted to an independent medical panel. The findings and outcomes in these cases are presented and compared. Seventeen of the 32 claims initially received compensation and four were subsequently accepted following appeals. Analysis of the medical basis of decision making indicated that seven claims were refused and at least four had their awards reduced as a consequence of inconsistent decisions. Arguable decisions resulted in five claims being refused and one award being reduced. Our experience illustrates problems inherent in the compensation system in South Africa. Initiation of a claim is expensive relative to wages in the industry, and awards are low since they are linked to wages (mean $60.47 per week). Processing of a claim took a mean of 13.8 months, while appeals for refusal to compensate took a further 29.8 months. It is argued that consensus medical definitions of compensable occupational disease should be used routinely and that provision must be made to facilitate entry of claimants into the compensation system.

Adult↗
PubMed1991

Silicosis among gemstone workers in South Africa: tiger's-eye pneumoconiosis.

Six cases of silicosis in workers involved in the processing of semiprecious gem stones have been seen in our clinic since 1976. They had been employed as stone sculptors in lapidaries where they processed tiger's-eye, rose quartz, amethyst, quartz crystal, and a variety of other locally occurring semiprecious stones. In five of the cases, exposure was in small and poorly regulated lapidaries without specific dust control measures. The sixth was detected during the course of a health and hygiene survey (including dust sampling) that was conducted in one of two lapidaries still operating in our area. Progressive massive fibrosis (PMF) or accelerated silicosis was noted in four of the six cases, three of whom had progression of their disease after cessation of exposure. With the development of PMF, the initial restrictive pulmonary function abnormalities were followed by steadily worsening airflow obstruction. Lung biopsies confirmed silicosis in three cases. Tuberculosis was confirmed in two cases and suspected and treated in a third. Workmen's Compensation was awarded in five cases. The survey confirmed that in semiprecious gem stone processing, the risk of silicosis appears to be confined to stone sculptors. Tried and proven techniques of general and local exhaust ventilation combined with water or oil to control dust at source were capable of effectively reducing dust emission to acceptable levels.

Adult↗
PubMed1990

Asthma and hyperthyroidism. A report of 4 cases.

For many years it has been known that thyrotoxicosis can worsen asthma, increasing both the frequency and severity of asthma attacks and increasing requirements for medication. Clinical recognition of this association may be difficult. Thyrotoxic asthmatics frequently experience side-effects from medications, particularly beta-receptor agonists and theophyllines. Four case reports of asthmatics in whom thyrotoxicosis was diagnosed are presented. All 4 patients improved on returning to euthyroid status. The mechanism responsible for the harmful interaction is not known.

Adult↗
PubMed1990

Comparison of dissection rates and angiographic results following directional coronary atherectomy and coronary angioplasty.

Directional coronary atherectomy is a new percutaneous transluminal technique for treating occlusive coronary artery disease. In this study, angiographic results (i.e., residual stenosis and angiographic evidence of postprocedure dissection) after directional coronary atherectomy and balloon angioplasty were compared. The atherectomy group consisted of 91 lesions in 83 consecutive patients who underwent either left anterior descending artery or right coronary artery atherectomy. The angioplasty group consisted of 91 lesions in 84 patients that were matched with the atherectomy lesions with respect to vessel and whether the lesion was a restenosis lesion. The mean preprocedure diameter stenosis was 76% in both groups as measured quantitatively with electronic calipers. After the procedure, the mean residual diameter stenosis of the atherectomy lesions was 13 +/- 17%, whereas for the angioplasty lesions it was 31 +/- 18% (p less than 0.001). Success rates in both groups were similar (94.5 and 93.4%, respectively). The incidence of postprocedure dissection was 11% in the atherectomy group and 37% in the angioplasty group (p less than 0.0001). Directional coronary atherectomy results in significantly improved postprocedure angiographic appearances due to significantly less severe residual stenosis and lower incidence of dissection.

Angioplasty, Balloon, Coronary↗
PubMed1989

Venous thrombosis and rifampicin.

In a retrospective analysis of clinically diagnosed and lower limb deep vein thrombosis (DVT) proven by contrast venography, DVT complicated admissions in 46 (3.4%) of 1366 adult patients treated in a tuberculosis hospital during 1986. Analysis of 7542 admissions during 1978-86 showed a relative risk of 4.74 in patients treated with regimens including rifampicin compared with other regimens. DVT was significantly more common in winter months and usually occurred within 2 weeks of treatment being started. This probable association between rifampicin and DVT does not contraindicate use of this drug, but measures to prevent DVT should be taken in inpatients receiving rifampicin.

Adolescent↗
PubMed1989

Byssinosis in South Africa. A survey of 2411 textile workers.

The first study of the prevalence of byssinosis in the South African cotton textile industry is described. Questionnaires were administered to 2411 subjects from six textile mills. Height and weight were measured and pulmonary function was tested before and after the first shift of a working week. Dust concentrations were measured using a Lumsden-Lynch vertical elutriator sampler. The prevalence of byssinosis (all grades) according to work departments was as follows: spinning 11.2%, winding 6.1%, and weaving 6.4%. Subjects with symptoms of byssinosis had a significantly reduced forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity ratio when compared with controls matched for age, height and weight. Dust concentrations in many areas of the preparation and spinning processes exceeded the World Health Organisation's recommended permissible exposure limit for cotton dust in spinning operations. The prevalence of byssinosis in this study appears to be lower than that documented elsewhere. The mill design, machinery in use and environmental conditions in the South African cotton textile industry appear to be similar to those in Egypt and the USA before 1978. South Africa differs from these and other countries, including the UK, in having an exceptionally high labour turnover rate, which has reduced exposure periods. The subjects were found to have a high prevalence of previously treated pulmonary tuberculosis (3.4% for males and 2.2% for females), and in this population this disease appeared to cause more respiratory impairment than byssinosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Intravascular ultrasound: catheter-based Doppler and two-dimensional imaging.

Intracoronary Doppler and two-dimensional imaging devices have been developed to aid in the search for more precise information about vessel pathology and local vessel hemodynamics. Measurement of coronary flow reserve using Doppler catheters has been well-validated experimentally and is being used clinically in certain groups of patients. Current designs using Fast-Fourier Transform of the signal and real-time video spectral display allows for instantaneous modification in positioning of the catheter within the artery to minimize artifacts. Studies are underway to assess whether measurement of coronary flow reserve and estimations of absolute flow add practical information to the quantitative assessment of vascular disease. Contrast angiography has been the "gold standard" for in vivo study of vascular disease. The recent development of two-dimensional imaging catheters has potentially opened up a new frontier of clinical assessment of vessel pathology. Imaging catheters can be used in a diagnostic role as a means of guiding therapeutic interventions. Direct analysis of the radiofrequency output of the catheter may allow for more precise characterization of plaque composition.

Angioplasty, Balloon↗
PubMed1985

Pharmacokinetic evaluation of the digoxin-amiodarone interaction.

Amiodarone is known to raise serum digoxin levels. This study was designed to evaluate the pharmacokinetic basis of this interaction in 10 normal subjects. The pharmacokinetic variables for digoxin were determined after a 1.0 mg intravenous dose of digoxin in each subject, before and after oral amiodarone, 400 mg daily for 3 weeks. During amiodarone administration, systemic clearance of digoxin was reduced from 234 +/- 72 ml/min (mean +/- standard deviation) to 172 +/- 33 ml/min (p less than 0.01). This was due to reductions in both renal clearance (from 105 +/- 39 to 84 +/- 15 ml/min) (p less than 0.05) and nonrenal clearance (from 130 +/- 38 to 88 +/- 20 ml/min) (p less than 0.01). Digoxin half-life of elimination was prolonged from 34 +/- 13 to 40 +/- 16 hours (p less than 0.05). Digoxin volume of distribution was not significantly changed. Amiodarone caused a three- to fivefold increase in serum reverse triiodothyronine levels, but changes in thyroid function were not quantitatively related to the changes in digoxin pharmacokinetics. These alterations in digoxin pharmacokinetics produced by amiodarone explain the increase in serum digoxin level that has been observed when this drug combination has been used clinically.

Adult↗