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Biomedical subjects

T J Clark

Publications and source records attributed to T J Clark.

At least 91 records · Page 5Linked to original sources
PubMed1982

Responses to cigarettes of various tar contents.

Specific conductance was measured before and within ten minutes of smoking a cigarette in 36 smokers on 210 occasions. Five types of cigarette were used including the equivalent of a 1956 unfiltered cigarette. Cigarettes were smoked in the smokers' usual fashion. Significant decreases in specific conductance occurred on only 19 occasions in 13 subjects and were most frequent with the cigarette with the highest tar content currently available. Examining the overall results the only significant change was an increase in specific conductance in the control, non-smoking period. We conclude that irritant qualities of tobacco smoke increase with tar content but airway narrowing lasting up to ten minutes is an uncommon event when cigarettes are smoked normally. Most smokers adapt to or avoid any sustained acute airway response to tobacco smoke whatever its tar content.

Airway Resistance↗
PubMed1981

An analysis of submaximal exercise responses in patients with sarcoidosis and fibrosing alveolitis.

An increase work rate exercise test was performed by 15 patients with sarcoidosis and by 20 patients with fibrosing alveolitis. The patients with sarcoidosis had a moderate reduction in total lung capacity (TLC) and transfer factor (DLCO), with chest radiographs showing widespread pulmonary infiltration but no evidence of fibrosis. The patients with fibrosing alveolitis had a significantly greater reduction in TLC and DLCO than those in the sarcoidosis group. Values for cardiac frequency (fH) and ventilation(V) were interpolated to the standard oxygen uptakes of 0.75, 1.0 and, where possible, 1.5 litres/min (33.5, 44.6 and 67 mmol/min respectively). The tidal volume at the ventilation of 20 and 30 litres/min was also determined. The exercise responses were compared to two groups of 20 normal men; each group being age matched to one group of patients. The fH at oxygen uptakes of 0.75, 1.0 and 1.5 litres/min were significantly higher in both patient groups than in the normal men. The submaximal indices for V were significantly greater in both patients groups than in the normal subjects at all three levels of oxygen uptake, and significantly greater in patients with fibrosing alveolitis than in those with sarcoidosis. The tidal volumes at 20 and 30 litres/min were smaller than normal in both patient groups but differences were removed by normalizing for differences in vital capacity. The maximum exercise ventilation measured in the patients with fibrosing alveolitis was significantly correlated with measurements of lung volume. Submaximal indices detect significant abnormalities during exercise in patients with pulmonary fibrosis and represent an alternative method for documenting abnormal exercise responses. Despite comparable radiological abnormalities the functional impairment in fibrosing alveolitis is much greater than in sarcoidosis. Thus the physiological abnormalities are not comparable quantitatively although they share a common qualitative difference.

Adult↗
PubMed1981

Regular versus symptomatic aerosol bronchodilator treatment of asthma.

Regular treatment with salbutamol or placebo aerosols was compared in a double-blind study in 18 asthma patients. Although symptom scores and respiratory function tests were not significantly different, wheezing attacks requiring additional puffs of a standard salbutamol aerosol were significantly more frequent during the period on placebo when patients were receiving symptomatic treatment only. Thus regular treatment with bronchodilator aerosols provides better control of asthma than symptomatic use alone.

Adult↗
PubMed1981

Influence of breath holding at total lung capacity on maximal expiratory flow measurements.

1. Forced exhalations performed from volumes below total lung capacity, so-called partial expiratory flow-volume curves, are suggested to be more sensitive in detecting airways bronchoconstriction than maximal expiratory flow-volume curves begun at total lung capacity. 2. In eight healthy men both maximal and partial expiratory flow-volume curves were measured where breath was held at total lung capacity of 70% of vital capacity respectively, for either 0 or 15 s before performing the forced exhalation. An histamine aerosol was used to provoke bronchoconstriction. 3. The results showed that the 15 s breath hold caused greater reduction in expiratory flow rates after histamine for both maximal and partial expiratory flow-volume curves than either manoeuvres performed with no breath hold. 4. A breath hold of 15 s at total lung capacity appeared to make the maximal expiratory flow-volume curve as sensitive as a partial expiratory flow-volume curve in detecting the response to histamine as well as providing measurements of forced expiratory volume in 1 s and vital capacity. Forced spirometry after a 15 s breath hold at total lung capacity therefore provides an easy and sensitive technique for detecting bronchoconstriction.

Airway Obstruction↗
PubMed1981

Pattern of breathing during cigarette smoking.

1. Recordings were made of the pattern of breathing during and after smoking a cigarette in 14 smokers and nine non-smokers. 2. The most consistent effect was an increase in tidal volume during smoking which reverted to baseline over 1-2 min. Changes in breath times were smaller and less consistent. Similar effects were observed with intermittent inhalations of charcoal. 3 In four subjects the tidal volume response was significantly decreased by oropharyngeal and laryngeal anaesthesia with lignocaine. 4. Filtration of particulate matter from the cigarette smoke delayed the onset of changes in tidal volume. 5. The changes probably represent an irritant response with stimulation at laryngeal or oropharyngeal level.

Adult↗
PubMed1981

Time course of response to prednisolone in chronic airflow obstruction.

Nineteen patients with chronic airflow obstruction measured their morning and evening peak expiratory flow (PEF) daily for 28 days. A placebo was taken for the first week and prednisolone 20 mg twice daily was taken for the last three weeks. The mean PEF in 13 patients who responded to prednisolone reached a maximum after eight days' treatment. The majority of the 19 patients had asthma and were thought to represent a typical cross section of patients who would be considered for a trial of oral corticosteroids. Most responsive patients will achieve a maximum response within eight days.

Adult↗
PubMed1981

Recovery of plasma corticotrophin and cortisol levels after three-week course of prednisolone.

Patients with chronic airflow obstruction were given a three-week course of prednisolone 40 mg per day. The basal plasma cortisol level and response to tetracosactrin were depressed after such a course. Basal plasma cortisol and corticotrophin (ACTH) levels were measured on five consecutive days after three weeks of treatment with prednisolone and were found to rise simultaneously to control levels within three days. Pituitary and adrenal functions were depressed for four days after short high dose courses of corticosteroids and patients may be at risk if they encounter stress during this time.

Adrenal Cortex Function Tests↗
PubMed1981

Automated system for the measurement of airways resistance, lung volumes, and flow-volume loops.

Using a digital computer and body plethysmograph measurements of airways resistance, lung volumes, and flow-volume loops may be obtained from a single manoeuvre performed by the patient. All the measurements together with a display of the flow-volume loop are displayed within 10 seconds of the patient completing the manoeuvre. The system appears to offer considerable advantages in speed, objectivity, and reproducibility when compared with conventional methods.

Airway Resistance↗
PubMed1981

Comparison of inhaled and intravenous terbutaline in acute severe asthma.

In patients with acute severe asthma, 5 mg of terbutaline by inhalation and 500 microgram intravenously in divided doses both produced equally effective but not maximal bronchodilatation. There was no difference in the production of side-effects. These results support the view that inhaled therapy can be as effective in patients with acute severe asthma as injected treatment. In view of the risks of intravenous treatment, especially using high doses, inhaled bronchodilator therapy would seem advisable as initial treatment.

Acute Disease↗
PubMed1981

A new method for computer-assisted determination of airways resistance.

Conventional methods for determining airways resistance, based on the recording of pressure and flow as X-Y displays, may yield inconsistent results because airways resistance is only one of a number of factors determining the shape of such displays. The temporal behavior of alveolar pressure and flow during panting suggests that the relationship between pressure and flow should be formulated in terms of differential equations. An equation is postulated to include terms characterizing resistance, gas inertance, and the behavior of the lungs as a number of parallel compartments with time constants that may be different. A simple algorithm allows these terms to be deduced from measured pressure and flow signals. Measurements obtained using the new method correlate well with those obtained using conventional methods. Variation of specific airways conductance is significantly reduced when compared with values obtained by conventional methods. Measured values for inertance agree well with theoretically predicted values.

Airway Resistance↗
PubMed1981

Sleep apnoea in diabetic patients with autonomic neuropathy.

Breathing during sleep was monitored in 8 diabetic patients with objective evidence of autonomic neuropathy and in 8 diabetic patients without neuropathy. Thirty or more periods of apnoea lasting 10 seconds or longer during one night's sleep were demonstrated in 3 of the diabetic patients with autonomic neuropathy. Such apnoeic periods may be related to the high incidence of cardiorespiratory arrests reported in such patients, particularly in association with anaesthesia or pneumonia.

Adult↗
PubMed1981

Comparison of intravenous and inhaled terbutaline in the treatment of asthma.

In a double-blind crossover controlled study, intravenous (IV) or nebulized terbutaline was given to eight patients with moderately severe asthma on two separate days. Four incremental doses of terbutaline were given by each route to establish a maximal effect. Both routes of administration produced significant increases increases in FEV1, FVC, PEFR, MEF50% single-breath TLC, and effective pulmonary blood flow. A decrease in slope of alveolar argon plateau was observed with both routes, but helium responsiveness showed variable changes with no significant or consistent effect seen. There was no significant difference between responses to incremental doses and maximal response apart from pulse rate, which rose during IV treatment. These results showed that the IV route had no advantage in terms of effectiveness or site of action over the inhaled route. Since IV treatment can produce systemic side effects, inhaled bronchodilator therapy should be used as the route of choice.

Adult↗
PubMed1980

Lung function and symptoms of cigarette smokers related to tar yield and number of cigarettes smoked.

In a survey of over 18 000 male civil-servants, tar yield and number of cigarettes smoked daily were related to lung function and respiratory symptoms. Both phlegm production and airflow obstruction among smokers increased with daily cigarette consumption. Tar yield influenced phlegm production but not the degree of airflow obstruction. However, those smoking more than twenty cigarettes per day lost most of the advantage of smoking low-tar cigarettes since their phlegm production was the same as that of high-tar cigarette smokers. Ex-smokers had better lung function than current smokers with comparable total cigarette consumption; the difference between ex-smokers and current smokers was not related to the length of time that ex-smokers had abstained from smoking. Despite a reduction in phlegm production a change to low-tar cigarettes, may only be associated with an improvement in lung function if dialy cigarette consumption is also reduced. After stopping smoking there may be an initial improvement in lung function but ex-smokers never fully restore their lung function, no matter how long they have abstained from smoking. Although lower tar yield may reduce phlegm production and the risk of cancer, the development of airways obstruction may not be related to the tar content of cigarettes. Rather, the gaseous phase of tobacco smoke may contain the irritant agents leading to airways obstruction.

Adult↗
PubMed1980

[Corticosteroid treatment of asthma].

Inhaled beclomethasone dipropionate (BDP) has proved to be an effective corticosteroid in the treatment of asthma, acting as if it were equivalent to about 5 to 10 mg of prednisolone per day but without the systemic side effects that may accompany oral treatment. The effectiveness of inhaled BDP is not associated with significant local side effects, the most common of which has proved to be oral candidiasis. There is no evidence to date that inhaled BDP promotes lung infection or damages the bronchial epithelium.

Asthma↗