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Biomedical subjects

A Cockcroft

Publications and source records attributed to A Cockcroft.

At least 55 records · Page 3Linked to original sources
PubMed1987

Voluntary isocapnic hyperventilation and breathlessness during exercise in normal subjects.

1. Nine normal subjects performed 6 min, constant-workload, exercise tests on a bicycle ergometer at either a 'high workload' or at a 'low workload'. During the first 'high workload' test their spontaneous breathing pattern was recorded on to magnetic tape. During one subsequent 'high workload' test and one 'low workload' test they voluntarily copied their recorded breathing pattern. During a second 'low workload' test they breathed spontaneously. Isocapnia was maintained by the operator throughout both the copying tests. During the exercise tests ventilation was recorded and subjects indicated the level of their sensation of breathlessness every 30 s. 2. Subjects felt markedly less breathless when a proportion of their ventilation was produced by voluntary effort than when the same total level of ventilation was produced entirely by the stimulus of exercise. Furthermore, voluntary isocapnic hyperventilation during exercise did not increase breathlessness above that normally associated with that level of exercise. 3. These results suggest that it is reflexly driven ventilation, and not simply the level of ventilation itself, which relates to the level of breathlessness during exercise.

Adult↗
PubMed1987

Radiological irregular opacities and coalwork exposure: a case-referent study.

Five hundred and fifteen men newly attending chest clinics in coalmining areas of England and Wales were entered into a study of the risk of irregular opacities on the chest radiograph in relation to occupation; readable radiographs were received for 489. The men completed questionnaires on occupational and smoking history and the radiographs were read for irregular opacities by the collaborating chest physicians and by a panel of three readers using the ILO 1980 classification. Older men had more irregular opacities than younger men, but coalworkers had a significant excess risk of nearly three times of having irregular opacities, which remained after stratifying for smoking and age. Lung cancer was evident on 14% of the radiographs and was significantly less common in coalworkers than non-coalworkers. The findings are consistent with a causal association between coalwork exposure and irregular opacities. Other evidence suggests that these opacities are associated with emphysema in coalworkers.

Adult↗
PubMed1987

Breathlessness.

Explore the source record for details and available documents.

Humans↗
PubMed1986

Central lymph node changes and progressive massive fibrosis in coalworkers.

Lungs from 123 coalworkers coming to necropsy were examined to determine the association between dust related changes in the central lymph nodes and progressive massive fibrosis and secondary foci in the lung parenchyma. Increasingly extensive changes of the central nodes were scored macroscopically, the highest scores indicating erosion through the walls of adjacent bronchi or branches of the pulmonary artery or both. In 88 cases (mainly with extensive changes) microscopic assessment was also made. Increasingly extensive changes of central nodes were associated with the presence of progressive massive fibrosis in the lungs (p less than 0.001) and the presence of secondary foci in lungs without progressive massive fibrosis (p less than 0.03). Microscopic assessments agreed fairly well with macroscopic assessments, but tended to be assigned lower scores. A hypothesis for the pathogenesis of progressive massive fibrosis is proposed whereby dust, accumulating in central lymph nodes, leads eventually to spread through the capsule and rupture into bronchi or pulmonary vessels, thereby sending dust laden activated cells back into the lungs to produce progressive massive fibrosis. These preliminary results are consistent with the hypothesis but more detailed studies are required.

Coal Mining↗
PubMed1985

Arterial oxygen desaturation during treadmill and bicycle exercise in patients with chronic obstructive airways disease.

Nine men with severe chronic obstructive airways disease (COAD), known to desaturate on exercise, performed a 6 min self-paced walk on a treadmill, followed by a bicycle exercise with workloads adjusted to mimic the oxygen consumption achieved on the treadmill. During both exercises, ventilation, oxygen consumption, carbon dioxide production, PaO2, PaCO2, pH and arterial lactate were measured and subjective breathlessness recorded. A reasonable match of oxygen consumption between the two exercises was achieved. In all subjects PaO2 fell to a lower level during treadmill compared with bicycle exercise. Ventilation, carbon dioxide production and arterial lactate were higher during bicycle exercise. Subjective breathlessness was greater during bicycle exercise, in proportion to the higher ventilation on the bicycle. The greater anaerobiosis occurring on the bicycle led to acidosis and an increased ventilation, minimizing the exercise fall in PaO2. Bicycle testing may seriously underestimate exercise desaturation occurring during level walking in patients with severe COAD.

Aged↗
PubMed1985

Breathlessness during different forms of ventilatory stimulation: a study of mechanisms in normal subjects and respiratory patients.

This study investigates the mechanisms underlying the perception of breathlessness induced by hypoxia and hypercapnia in both naive normal subjects and patients with respiratory mechanical problems. In normal subjects separately receiving both oscillating hypercapnic and hypoxic ventilatory stimulation, equivalent peak stimulus intensities in end-tidal gas were associated with a 'damped' ventilatory response when the frequency of stimulation was increased. A concomitant fall in peak breathlessness levels on a visual analogue scale was recorded in each case. In normal subjects and patients, the voluntary copying of a ventilatory pattern recorded during oscillating hypercapnic stimulation was associated with a marked diminution or complete absence of breathlessness despite equivalent levels of peak ventilations achieved. Voluntary copying of hypercapnic stimulated ventilation was not associated with any demonstrable change in the distribution of muscle movements between the chest wall and abdomen. These results suggest that the intensity of breathlessness depends on the level of effective reflex stimulation of the respiratory-related neurones in the medulla. They cannot be explained solely in terms of perception of afferent neural information arising from either chemoreceptors or respiratory mechanoreceptors.

Abdomen↗
PubMed1985

A self paced treadmill walking test for breathless patients.

A treadmill exercise test is described that retains the advantages of self paced walking but allows the measurement of cardiorespiratory variables. A horizontal treadmill was modified to allow patients to control their own speed. During exercise continuous measurements of speed, distance, heart rate, arterial oxygen saturation, and stride length were made and subjective assessments of breathlessness were recorded on a visual analogue scale. Ten men with severe chronic obstructive lung disease performed a 12 minute corridor walk and a self paced 12 minute treadmill walk on the same day and repeat treadmill walks on different days. Six of them performed three walks or more. Six patients had ventilatory measurements during treadmill exercise. There was no significant difference (p greater than 0.1) in the distance covered during corridor and treadmill walks, and distances on the treadmill were repeatable after the first walk. Use of a mouthpiece significantly reduced the distance covered on the treadmill. The self paced treadmill walk is a simple repeatable test and has advantages over both a corridor walking test and standard progressive tests for assessment of breathless patients.

Aged↗
PubMed1984

Recycling of transferrin receptors in A431 cells is inhibited during mitosis.

There is a marked reduction in the number of surface transferrin receptors as A431 cells enter mitosis which persists until telophase when receptors reappear to a level that exceeds the original interphase value. This is most simply explained by assuming that recycling of receptors back to the cell surface is inhibited as cells enter mitosis but that internalisation continues for a short while, causing surface receptor depletion. In telophase recycling would resume before internalisation giving a temporary excess of surface transferrin receptors.

Carcinoma, Squamous Cell↗
PubMed1983

Prevalence and relation to underground exposure of radiological irregular opacities in South Wales coal workers with pneumoconiosis.

A total of 124 coal workers and ex-coal workers receiving disability benefit for coal worker's pneumoconiosis and routinely reattending the Cardiff Pneumoconiosis Medical Panel during a 10-week period were studied. Those with complicated pneumoconiosis were excluded. Their current chest radiographs and their chest radiographs at the time of certification were read in random order by three readers using the 1980 ILO Classification of Radiographs. An irregularity score was derived from the readings. The x-ray findings were examined for changes since certification and for relationships with age, smoking, and underground coal work exposure. One-fifth of the current radiographs showed mainly irregular opacities, whereas nearly all of those from the time of certification showed mainly irregular opacities, whereas nearly all of those from the time of certification showed mainly rounded opacities. Irregular opacities were related to age, smoking, and underground exposure. The exposure effect remained after excluding the older men. The findings suggest that radiological irregular opacities, and their associated pathology and lung function changes, commonly develop in coal workers with pneumoconiosis and should be considered part of the condition.

Adult↗
PubMed1982

Post-mortem study of emphysema in coalworkers and non-coalworkers.

A post-mortem survey of emphysema in coalworkers and non-coalworkers was carried out in men aged 50-70 years dying of ischaemic heart disease (IHD). It was determined that in such men selection for necropsy was similar in coalworkers and non-coalworkers. All lungs were examined in a standard way and the amounts of centrilobular and panacinar emphysema were scored on numerical scales. Emphysema in men dying of IHD was significantly more frequent in coalworkers than in non-coalworkers even after age and smoking habits were accounted for by stratification. In the coalworkers, the severity of emphysema was related to the amount of dust in simple foci in the lungs. Because both groups were selected similarly from their parent populations the relative frequency of emphysema found in this study reflects that in the whole populations of coalworkers and non-coalworkers in the study area and confirms an excess of emphysema in coalworkers. This excess is likely to be due to occupational factors.

Aged↗
PubMed1982

Shape of small opacities and lung function in coalworkers.

Lung function and chest radiographs were reviewed in 357 coalworkers who had been referred from the Cardiff Pneumoconiosis Medical Panel. The chest films were read according to the 1980 ILO classification of radiographs by three experienced readers. An irregularity score, reflecting the shape of the small opacities, was derived from the readings and compared with the lung function variables. Men with higher irregularity scores had significant reductions in ventilatory capacity and gas transfer factor, with no change in total lung capacity, after age, height, profusion of small opacities, and smoking habit had been taken into account. The effects were present both in those with and in those without large opacities. The agreement between readers over the shape of opacities was almost as good as for their profusion. Men with rounded opacities had a lower gas transfer factor if they were predominantly of the "p" type. The results are consistent with those for a combination of emphysema and interstitial fibrosis, which has been found in coalworkers with irregular opacities.

Adult↗
PubMed1982

Psychological changes during a controlled trial of rehabilitation in chronic respiratory disability.

Thirty-four men with chronic respiratory disability took part in a randomised, controlled trial of physical training. The control group also undertook exercise training after their control period. During the study measurements were made of exercise tolerance (12-minute walking distance) and the men completed two psychology questionnaires. Walking distance improved significantly more in the treatment group than in the control group. Both groups recorded scores suggesting psychological "improvement" and the changes in the two groups were not significantly different from each other. There were no consistent associations between the increase in walking distance and changes in psychological scores. Initial psychological scores were not useful in predicting changes in walking distance. The results suggest that the effect of treatment on walking distance was not psychological.

Clinical Trials as Topic↗
PubMed1981

Allergy in laboratory animal workers.

179 people working with small laboratory animals were studied by questionnaire, lung-function tests, skin tests with common allergen extracts and extracts of the serum and urine of five animal species, and serology. 49 people had symptoms related to animal contact, most commonly rhinitis but also asthma and skin rashes. Skin reactivity to animal extracts was related to symptoms, particularly asthma, but many people with rhinitis only had negative skin tests. Positive skin tests without symptoms were rare. 3 people had additional late skin reactions. Atopic individuals were no more likely than non-atopics to have animal-related symptoms but were more likely to have asthma. Gel diffusion revealed no precipitating antibodies, and no specific IgG was detected with the ELISA technique. Lung-function measurements were normal. Sensitisation to laboratory animals may involve heavy antigen exposure, so that relatively unreactive individuals can be affected. Exclusion of atopic individuals from work with laboratory animals will not eliminate the problem.

Animals↗
PubMed1981

Inhalation challenge in humidifier fever.

When exposed to an amount of contaminated humidifier water roughly equivalent to that inhaled over an 8-hour period at their work place, four out of six subjects developed symptoms of humidifier fever. Two non-exposed subjects failed to react to the same challenge. Characteristic lung function, temperature and leucocyte changes were recorded; however, a fall in gas transfer previously reported was not seen. That the reaction was immunologically mediated and not due to endotoxin activity was shown by a negative pyrogen response in rabbits inoculated intravenously with concentrated humidifier water. The nature of the immune response has not as yet been evaluated but it does not reside with the ability of humidifier fever antigens to activate complement. Skin testing produced an immediate weal and flare in the four subjects with precipitins and may reflect the presence of short-term anaphylactic IgG antibody.

Animals↗
PubMed1981

An investigation of operating theatre staff exposed to humidifier fever antigens.

Sixty staff working in a hospital operating theatre, where a case of humidifier fever had been identified, were studied together with 49 subjects working in other parts of the hospital. They each had a blood test for serology, a skin test, and a chest radiograph and completed a questionnaire. The theatre staff also had pulmonary function tests. The theatre humidifier was found to contain several organisms including amoebae and antigens cross-reacting highly with those implicated in previous outbreaks of humidifier fever. Of the 60 exposed subjects, 25 had developed antibodies, nine had probable symptoms of humidifier fever, and six possible symptoms. There was a strong association between symptoms and antibodies (p = 6 x 10(-5) by Fisher's exact test). The development of antibodies was also related to duration of exposure in the theatre (p less than 0.01 by X2 test for trend) and inversely to smoking (p = 0.0073 by Fisher's exact test) but not to history of atopy. Because of the presence of antigens and because certain biocides added were ineffective in controlling antigenic build-up the humidifier was switched off. Eight months later specific IgG levels in the theatre staff sera, estimated by an enzyme-linked immunosorbent assay technique, had fallen on average by 25%. Inhalation challenge with humidifier water was performed in eight subjects. Four subjects reacted to the challenge, including both those with antibodies and previous symptoms.

Air Conditioning↗
PubMed1979

Is appendicitis familial?

A family history of appendicectomy was sought in two groups of children admitted to Llandough Hospital over sixteen months. The study group consisted of 29 children with histologically confirmed acute appendicitis, while the control group consisted of 29 children admitted for reasons unrelated to abdominal pain. A history of appendicectomy was elicited in first-degree relatives--that is, siblings and parents of 20 of the children in the study group and of four of the controls--a statistically significant difference. The results obtained from this study suggest that a familial predisposition to appendicitis exists.

Acute Disease↗
PubMedDate not supplied

Surgeons who test positive for hepatitis C should not be transferred to low risk duties.

Current UK guidelines allow surgeons who are antibody-positive for hepatitis C virus (HCV) to continue performing exposure-prone procedures (EPPs) unless they have been shown to transmit HCV to a patient. Given the low rate of recognised transmission from surgeon to patient, this recommendation is probably reasonable and is consistent with the management of eAg negative carriers of hepatitis B who are also allowed to continue operating. It seems likely that, in the future, pressure will increase to remove surgeons who are HCV-positive (or positive for HBsAg without HBeAg or HIV-positive) from the list of those able to perform EPPs. If implemented, this would require surgeons to be tested at regular intervals for HCV status. There are no data to demonstrate that such an approach would benefit patients overall and the ethical costs would be high because many surgeons will have acquired HCV occupationally. The financial costs would also be high and, in my opinion, would be better deployed by ensuring that existing simple preventative measures are routinely applied to prevent patient-surgeon-patient transmission of all blood-borne viruses.

Hepatitis C↗