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Biomedical subjects

T J Clark

Publications and source records attributed to T J Clark.

At least 127 records · Page 7Linked to original sources
PubMed1977

Do sympathomimetic amines prevent exercise-induced asthma by bronchodilatation alone?

Seventeen patients with exercise-induced asthma were studied. Eleven patients (cases 7-17), of whom seven were atopic subjects, were given isoetharine or isoprenaline and were subsequently tested for exercise-induced asthma after bronchodilatation had ceased. In two atopic and one non-atopic patients protection was observed which could not be attributed to chance. Two of these three patients were studied again and this phenomenon was repeatable. Prevention of exercise-induced asthma 30 min after inhalation of isoetherine and sodium cromoglycate was compared in 10 patients (cases 1-10), of whom six were atopic subjects. There was no significant difference in the results and protection from isoetharine was not related to the magnitude of its bronchodilator effect. These results suggest that beta-adrenergic agonists may have both bronchodilator and other actions in exercise-iduced asthma. Whether these other actions are anti-alergic is unknown.

Adolescent↗
PubMed1977

Comparison of salbutamol Rotahaler with conventional pressurized aerosol.

Salbutamol in a powder aerosol from the Rotahaler insufflator was compared, with equal doses of the conventional pressurized aerosol by dose-response curves and in a 1 month open trial, in the treatment of asthma patients with good inhalation technique. Results were not significantly different in either study. A further group of asthma patients, who were known to be incapable of using pressurized aerosols effectively, were shown to benefit from treatment with the Rotahaler. This device should increase the value of the sympathomimetic drugs to the minority of asthma patients who cannot use conventional aerosols correctly.

Administration, Intranasal↗
PubMed1977

Intrasubject variability of maximal expiratory flow volume curve.

Analysis of airflow in the terminal portion of the maximal expiratory flow volume curve has been suggested as a useful test for the early diagnosis of chronic airways obstruction. Whether such an analysis can identify early disease, and whether any subsequent action can prevent the progress of chronic airways obstruction, is unknown and will require prospective studies. As a precursor of such a study we have tried to establish the intrasubject variability of those tests of forced expiration which may be used for screening. We therefore measured expiratory flow volume curves of five healthy males and five healthy females aged 20-30 years as this is an age-group in which early detection of airways obstruction may be of value. Flow volume curves were obtained on the same day of the week for six weeks, and on three separate days during this period we carried out three flow volume curves every hour from 9 am to 6 pm. The data were subjected to analysis of variance to determine the variability of each measurement. Data were collected from forced expired volume in one second (FEV1) forced vital capacity (FVC), maximum expiratory flow rates at 50% and 75% of expired vital capacity, and forced expiratory time (FET). The results showed no consistent pattern of diurnal variation over the working day. The variation in any subject for FEV1 and FVC over the study period was considerably less than variations detected in the maximal expiratory flow rates at 50% and 75% of the expired vital capacity and FET. Our results suggest that the intrasubject variation found in flow rates of the terminal portion of the maximal expiratory flow volume curve and forced expiratory time may limit the usefulness of these tests in detecting early airways obstruction. FEV1 and FVC are more reproducible tests and are therefore particularly suited for cross-sectional screening. The more sensitive maximal expiratory flow volume curve may, however, be more useful for long-term studies in individuals when the onset of disease is sought, or for short-term challenge studies requiring the most sensitive index of change in airway characteristics.

Adult↗
PubMed1977

Physiological patterns in early morning asthma.

Sixteen asthmatic patients who regularly showed early morning falls in peak expiratory flow rate of more than 25% were studied at 06.00 hours and 14.00 hours. At 06.00 hours considerable deterioration in static lung volumes and airways resistance occurred which was typical of an attack of acute asthma. Blood gas analysis showed less variation, with mild hypoxia and a wide alveolar-arterial oxygen tension gradient throughout the study. Diurnal variation was also seen in the response of maximal mid expiratory flow rates to the inhalation of helium/oxygen mixture in seven patients, but another seven were consistently non-responders. The overall pattern of results suggests that the calibre of both large and small airways decreased at night but improvement was more complete in large airways during the day. Despite these findings patients had few symptoms at 06.00 hours when most of them showed marked reversibility after inhaling aerosol salbutamol. This phenomenon might account for the sudden nature of some asthma deaths as these often occur in the early morning. If this is the case, the minority of patients whose early morning decline in lung function was not immediately reversible would appear to be at greatest risk.

Adult↗
PubMed1976

Sleeping ventilatory patterns in patients with severe chronic airflow obstruction causing respiratory failure.

During sleep some patients with airways obstruction and hypoxaemia developed tachypnoea. This could not be explained by the severity of their abnormality of lung function, their CO2 responsiveness, the nature of their lung disease or their personality. This nocturnal tachypnoea correlated best with a raised resting arterial blood PCO2, and was not seen hypoxaemic patients with a normal PCO2 who showed the usual fall in respiratory rate when asleep. We suggest that in patients with both hypoxaemia and hypercapnia sleep removes a cortical inhibitory mechanism which slows breathing durigng waking hours, and is linked to the arterial blood PCO2.

Airway Obstruction↗
PubMed1975

Airway function in healthy subjects and patients with left heart disease.

1. In forty non-smoking healthy subjects and seventy-two patients with left heart diseases measurements were made of the volume expired in the first second of a forced expiration (FEV1) and the total volume expired in a forced expiration (FVC) before and after inhalation of salbutamol. Before and after salbutamol the healthy subjects and patients also inhaled maximally an inspirate, the first part of which contained 133Xe and, during controlled expiration, the radioactivity of the expirate was measured and plotted against its volume. the resulting curves were divided into phases of different slope by eye, the point at which phase 3 changed to phase 4 being nominated the closing volume. 2. In forty non-smoking healthy subjects inhalation of salbutamol was followed by significant increase in FEV1 but FVC and closing volume did not change. 3. Change in posture from seated erect to supine in thirty of these healthy subjects was accompanied by significant reduction in FEV1 and FVC and as closing volume was not significantly different in the two positions the ratio closing volume/vital capacity was increased with recumbency. 4. In seventy-two patients with left heart diseases without a history of cough or wheeze, FEV1, FVC, closing volume and the ratio closing volume/vital capacity were significantly different from values in the healthy subjects. There was no significant difference between non-smokers and ex-smokers amongst the patients. 5. Significant increase in FEV1, FVC and reduction in closing volume and the ratio closing volume/vital capacity followed inhalation of salbutamol in patients with heart diseases but the values remained significantly different from those recorded in the healthy subjects. 6. In twenty patients with heart diseases, FEV1 and FVC were reduced by change in posture from seated erect to supine but the ratio closing volume/vital capacity and the regression with age of this ratio were not significantly changed by change in position. 7. In patients with heart diseases the ratio closing volume/vital capacity was significantly correlated with severity of breathlessness and length of symptom-history but not with left ventricular end-diastolic or pulmonary vein wedge pressures.

Adult↗
PubMed1975

Effect of atropine on sputum production.

The effect of atropine on sputum production has been studied in patients with asthama, chronic bronchitis, and bronchiectasis in some of whom there was bronchorrhoea. In three patients a reduction in sputum volume was observed after atropine but it would seem that the decrease was mainly due to the inhibitory effect on salivary secretion which facilitates spitting. The one patient treated with long-term oral atropine showed a marked reduction in sputum volume although chemical constituents and viscosity levels remained unchanged, suggesting that in this case atropine had an inhibitory effect on bronchial gland secretion.

Adolescent↗
PubMed1975

Clinical relevance of the flow rate response to low density gas breathing in asthmatics.

The maximal expiratory flow rate response to low density gas breathing was examined at the mid-vital capacity point in 31 asthmatic patients. Clinical features and long-term follow-up date were documented to assess the clinical relevance of the various responses. Many of the patients with chronic asthma had not responded adequately to outpatient therapy, and they had been admitted to hospital for evaluation and management. With increased steroid doses and intensive bronchodilator therapy, all showed considerable improvement and were studied when this improvement occurred. The remainder of the patients were studied after recovery from acute asthmatic attacks or during maintenance management as outpatients. All patients with a forced expiratory volume in 1 second is greater than 75 per cent of the predicted value and mid-expiratory flow rate is greated than 50 per cent of the predicted value at the time of study showed a good response to helium. Those patients with more severe obstruction could be divided into 2 groups, responders and nonresponders. A qualitatively similar response to normal subjects (density-dependent flow rates) was a feature of those patients who in general showed further improvement in ventilatory function on follow-up. A qualitatively similar response to that seen in patients with chronic irreversible obstruction (density-independent flow rates) was a feature of those patients who in general showed no further improvement in ventilatory function on long-term follow-up. There were, however, exceptions to both groups. We conclude that in asthmatics with more than mild air flow obstruction, the assessment of helium response can be of value in identifying those patients who have, in addition to asthma, chronic irreversible obstruction due to concommitant chronic bronchitis and/or emphysema. Clinical assessment and measurement of single-breath diffusion of carbon monoxide provide additional support for the latter diagnoses and separate the few exceptions from the bulk of the nonresponders. Responders and nonresponders can be fairly reliably identified from the simply recorded exhaled flow volume curve, thus obviating the need for a volume displacement plethysmograph.

Acute Disease↗
PubMed1975

A case of primary alveolar hypoventilation associated with mild proximal myopathy.

A 34-year-old man presented with clinical features of primary alveolar hypoventilation, but was found additionally to have an adult onset myopathy caused by acid maltase deficiency. This was not severe, as judged clinically, and was initially overlooked. His vital capacity and sprint maximal ventilatory volume were only slightly reduced, and the ventilatory response to CO2 was virtually absent. There was, however, a mild impairment in the ability to decrease Pco2 to normal by voluntary hyperventilation. The relation of myopathy and alveolar hypoventilation is discussed, and it is proposed that the primary muscle disease predisposed the patient to the development of the ventilatory abnormality.

Adult↗
PubMed1975

The use of corticosteroids in the treatment of acute asthma.

A study of 23 patients admitted to hospital with severe acute asthma is reported in which plasma cortisol level on admission was significantly correlated with the degree of acidaemia and pulse rate. Patients who had not previously received treatment with corticosteroids responded satisfactorily to repeated daily injections of tetracosactrin depot, the rate of improvement being comparable to that observed in other patients treated with intravenous hydrocortisone hemisuccinate. A prompt and sustained rise in plasma cortisol was also seen following tetracosactrin. The total daily dose of hydrocortisone required to achieve plasma cortisol levels above 100 mug/100 ml was less when given by continuous intravenous infusion compared with intermittent injections, and a regime of 3 mg/kg body weight every six hours by infusion appeared satisfactory. Most patients reported subjective improvement by about four hours after starting treatment but objective evidence did not appear until about six hours from the start. Measurements of FEV1 and FVC proved to be the most reliable indices of the beginning of improvement although pulse rate was the first index to show maximum improvement. Previous maintenance treatment with corticosteroids in patients with asthma did not appear materially to affect the plasma half-life of intravenous hydrocortisone (4 mgm/kg body weight) when compared with healthy subjects or other patients with asthma who had not previously been treated with corticosteroids.

Acute Disease↗