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Biomedical subjects

R I Stewart

Publications and source records attributed to R I Stewart.

At least 19 recordsLinked to original sources
PubMed1991

The standard of spirometry in the RSA.

Standards for high-quality lung function testing have not yet been formally adopted in the RSA, despite the increase in the performance of spirometry. A study was undertaken to determine the standard of spirometry in clinical practice in this country. Forty-five spirometer users agreed to participate. Responses to a questionnaire, administered by personal interview, were graded according to the proportion of correct or appropriate answers: completely unsatisfactory less than 33.3%; poor 33.3-66.6%; and satisfactory greater than 66.6%. Only 6 spirometers were regularly calibrated. Knowledge of international standards for spirometry, the basic working mechanism of the spirometer being used and calibration ranged from poor to completely unsatisfactory in most of the practices. Instructions to the patients for performing the manoeuvres were satisfactory, but elevation of the result for acceptability, reproducibility, selection of the best test and diagnosis of a positive bronchodilator response were generally completely unsatisfactory. Only 18 practitioners knew the source of the reference values they used and 5 had proved their validity with a sample. Fourteen of the 45 practitioners were unable to make the correct diagnoses from two typical test results. Of the 45 practitioners, 40 were interested in a course in practical, clinical spirometry. In the light of the predominantly unsatisfactory results obtained in this study, we consider clinical spirometry to be an urgent priority for all levels of medical education.

Clinical Competence↗
PubMed1990

[The influence of exercise-induced bronchoconstriction on participation in organized sport].

Approximately 70-80% of all asthma sufferers develop acute airway obstruction with exercise, while at least 7% of children in the general population develop exercise-induced bronchoconstriction. The purpose of this study was: (i) to determine whether children in the Cape Peninsula who suffer from asthma and/or exercise-induced bronchoconstriction are as inactive and uninvolved in sport as asthmatic children in the USA; and (ii) whether this uninvolvement is a direct result of their susceptibility to exercise-induced bronchoconstriction. An in-depth study was done on the intensity, frequency and level of participation in sport by children with asthma and/or exercise-induced bronchoconstriction compared with a control group of healthy children without a history of asthma or exercise-induced bronchoconstriction. Children with asthma and/or exercise-induced bronchoconstriction generally maintained a similar level of sport participation as healthy children, and only children with serious asthma or exercise-induced bronchoconstriction experienced limitations with regard to physical activity. It was found that, in contrast to children in the USA, non-participation in sport could not be explained by asthma and/or exercise-induced bronchoconstriction.

Adolescent↗
PubMed1990

The prevalence of exercise-induced bronchoconstriction in Cape Town schoolchildren.

An attempt was made to determine: (i) the prevalence of exercise-induced bronchoconstriction among white and coloured schoolchildren in Cape Town; and (ii) the validity of an exercise test for the diagnosis of asthma in the general population. Children (698 white and 494 coloured) were randomly drawn from schools in the northern suburbs of Cape Town. Each child participated in a standard 6-minute exercise test and spirometric measurements were taken before and 10 minutes after exercise with a portable spirometer. The diagnosis of asthma was based on a questionnaire and personal questioning and included those children who, in the past or at present, suffered episodic or continuous airflow obstruction, which was responsive to a bronchodilator. The criterion for the diagnosis of exercise-induced bronchoconstriction was a 10% decline in forced expiratory volume in 1 second after exercise. The prevalence of exercise-induced bronchoconstriction was significantly higher among white children (5.87%) than coloured children (4.05%). The sensitivity of the exercise test was 0.31 and the specificity 0.97. In contrast to the results of hospital-based studies, the negative predictive value of an exercise test (95%) was found to be greater than the positive predictive value (46%). It is therefore concluded that exercise testing is not a useful screening test for epidemiological use; it is probably useful as a challenge test for detecting asthma in the individual patient when the likelihood of the disease is high.

Adolescent↗
PubMed1990

Assessment of the 2.4 km run as a predictor of aerobic capacity.

Since the 2.4 km run time test is routinely used in military training programmes as an indicator of aerobic capacity and its possible improvement, an attempt was made to: (i) establish a regression equation of VO2max v. 2.4 km run time in a group of 20 young military volunteers; and (ii) determine whether this equation could be used to predict VO2max reliably from the 2.4 km time obtained from another group. Before and after training, VO2max was measured in all subjects using a treadmill test, and 2.4 km run time was determined in the field. Linear regression equations using the 2.4 km run time as the independent variable accounted for 76-92% of the variance in VO2max, while the standard error of the estimate varied from 2.24-2.91 ml/kg/min. In the second test group, the directly measured VO2max was 59.89 +/- 0.99 ml/kg/min, while the mean value estimated from the regression equation of the first group was 59.61 +/- 1.16 ml/kg/min (P less than 0.001). It was concluded that, in the population studied, the 2.4 km run time in the field reliably predicts VO2max measured during treadmill exercise in the laboratory.

Adolescent↗
PubMed1990

Weight loss in obese women--exercise v. dietary education.

It was postulated that a nutrition-education programme was as effective an adjunct to a diet-based weight-loss programme as an exercise regimen. Forty-five obese female volunteers were placed on the same 5,000 kJ diet and were then assigned to each of three therapy groups: (i) an exercise group, involving three 1-hour exercise sessions per week (15 women); (ii) a lecture group involving a weekly 1-hour group lecture session (15); and (iii) a control group (15) who received only the diet and no activity. Weight loss, body fat loss (%) and daily energy intake reductions were equally reduced in the subjects in all three groups who completed the programme. There was, however, a significantly higher dropout rate in the control group. Taking this into account, the weight loss in the two test groups was similar and greater than that of the control group. We conclude that, in the short term, dietary education was as effective as exercise in promoting dietary compliance and weight loss.

Adult↗
PubMed1990

Human chorionic gonadotrophin and weight loss. A double-blind, placebo-controlled trial.

Low-dose human chorionic gonadotrophin (HCG) combined with a severe diet remains a popular treatment for obesity, despite equivocal evidence of its effectiveness. In a double-blind, placebo-controlled study, the effects of HCG on weight loss were compared with placebo injections. Forty obese women (body mass index greater than 30 kg/m2) were placed on the same diet supplying 5,000 kJ per day and received daily intramuscular injections of saline or HCG, 6 days a week for 6 weeks. A psychological profile, hunger level, body circumferences, a fasting blood sample and food records were obtained at the start and end of the study, while body weight was measured weekly. Subjects receiving HCG injections showed no advantages over those on placebo in respect of any of the variables recorded. Furthermore, weight loss on our diet was similar to that on severely restricted intake. We conclude that there is no rationale for the use of HCG injections in the treatment of obesity.

Adipose Tissue↗
PubMed1988

Carbon monoxide diffusing capacity in asthmatic patients with mild airflow limitation.

The aim of this study was to test the hypothesis that carbon monoxide diffusing capacity (DCO) is elevated in asthmatic patients with minimal airflow limitation and/or hyperinflation; the latter factors should reduce the possibility of technical errors in the measurement of DCO. In ten asthmatic and ten healthy subjects, DCO and its components, membrane diffusing capacity (Dm) and pulmonary capillary blood volume (Qc) were measured by the single-breath method. Values were normalized for alveolar volume (VA). The mean DCO/VA was higher in the asthma groups as was the Qc/VA. The Dm/Qc was also higher in the asthma group. In the asthmatic but not the healthy subjects, both DCO/VA and Qc/VA were negatively correlated with the forced expiratory flow at 50 percent of vital capacity and peak inspiratory flow rate. Thus, DCO/VA may be increased in asthmatic patients with only mild airflow limitation; this may be due to an elevated capillary blood volume.

Adult↗
PubMed1987

The adult respiratory distress syndrome in association with diabetic keto-acidosis. A case report.

A 41-year-old man presented in stupor, with ketoacidosis and acute severe respiratory failure. He had a history of alcohol abuse and had been on insulin therapy for diabetes secondary to chronic pancreatitis for 11 years. the condition was rapidly progressive and the patient died within 5 hours of presentation of profound hypoxia and hypotension despite aggressive therapy. Autopsy confirmed the clinical diagnosis of 'shock lung'. None of the more commonly associated precipitating factors of adult respiratory distress syndrome could be detected clinically or at autopsy and the pathogenesis of the condition remains elusive.

Adult↗
PubMed1987

Serum alpha-1-protease inhibitor activity and pulmonary function in young insulin-dependent diabetic subjects.

Abnormalities of lung function have previously been described in patients with impaired alpha 1-protease inhibitor (alpha 1-PI) function and more recently in insulin-dependent diabetic subjects. This study was undertaken to test the hypothesis that impaired alpha 1-PI activity may be implicated in the pathogenesis of lung function abnormalities in young insulin-dependent diabetic patients. Twelve young (16.23 +/- 4.51 years), non-smoking insulin-dependent diabetic subjects and 12 reference subjects were evaluated in respect of lung mechanics, absolute serum alpha 1-PI levels and the functional ability of alpha 1-PI to inhibit elastase. Results of the ventilatory mechanics showed that the mean value for the volume-independent index of lung elasticity Kst(L) was significantly greater in the diabetic group (0.149 +/- 0.05 vs. 0.116 +/- 0.03; p less than 0.05). The absolute serum alpha 1-PI levels in the insulin-dependent diabetic subjects was significantly lower than in reference subjects (1.74 +/- 0.11 vs. 2.06 +/- 0.09 g/l; p less than 0.05). While the specific alpha 1-PI activity of the diabetic sera showed no significant difference from that of the reference sera, the total alpha 1-PI inhibitory activity in the diabetic sera was significantly lower than reference values (201.9 +/- 9.7 vs. 246.9 +/- 13.5 U/L; p less than 0.02). Although these findings indicate impairment of both ventilatory mechanics and alpha 1-PI activity in the insulin-dependent diabetic subjects, the pathogenesis of these findings and their functional implications are at present unknown.

Adolescent↗
PubMed1987

Cross-section study of pulmonary function in patients with insulin-dependent diabetes mellitus.

In this study, we attempted to establish the prevalence and nature of pulmonary dysfunction in a cross section of a diabetic population and the relationship of pulmonary dysfunction to diabetic factors and complications. Forty insulin-dependent diabetic patients, 15 to 60 yr of age, and 40 healthy reference subjects, matched for age, sex, and race, were studied. All subjects were lifelong nonsmokers and had no clinical evidence of past or present respiratory disease. Lung function was assessed from the flow-volume curve, single-breath nitrogen washout, static lung elastic recoil, and pulmonary diffusing capacity (DLCO/VA) and its components: membrane diffusing capacity (Dm/VA) and pulmonary capillary blood volume (Qc/VA). The diabetic patients had an increased value for Kst(L) and in Kst(L), the exponential shape constant of the pressure-volume curve compared with that of the reference subjects (Kst(L), 0.184 +/- 0.011 versus 0.135 +/- 0.005; p less than 0.005, mean +/- SEM). The DL/VA was lower in the diabetic subjects (4.62 = 0.12 versus 5.31 +/- 0.10 ml/min/mm Hg/L; p less than 0.001), and this was due to a lower Qc/VA (9.45 +/- 0.43 versus 11.75 +/- 0.35 ml/min; p less than 0.001). The Kst(L) and Qc/VA were correlated with the duration of diabetes. The In Kst(L) was negatively correlated with both DL/VA (r = -0.32, p less than 0.05) and Qc/VA (r = -0.36, p less than 0.05). There was no association between abnormal pulmonary function and the presence of other diabetic complications. It is concluded that there are mild, duration-related abnormalities of lung elastic recoil and pulmonary diffusing capacity and a reduction in pulmonary capillary blood volume in insulin-dependent diabetes mellitus.

Adolescent↗
PubMed1986

Breath holding in divers and non-divers--a reappraisal.

The two phases of breath holding, the voluntary inactive and involuntary active phases, were identified by non-invasive methods using the induction plethysmograph. Eight trained divers and 7 non-diving control subjects familiar with respiratory apparatus were studied. During breath holding from normocapnia and total lung capacity it was not possible to distinguish between the two groups in respect of the pattern or duration of breath holding or alveolar gas tensions at the breakpoint. Divers could, however, hold their breath much longer after hyperventilation (165 +/- 40.0 and 121 +/- 31.4 seconds; P less than 0.01). This was associated with a longer second phase than occurred in non-divers (78.0 +/- 29.7 and 17.6 +/- 13.1 seconds; P less than 0.01) and more severe alveolar hypoxia (percentage oxygen 7.6 +/- 1.8 and 10.9 +/- 1.7%; P less than 0.01). It is concluded that these divers had a hyperventilation-dependent attenuated hypoxic ventilatory response. Subjects could also be identified who have either a very short (less than 10 seconds) or very long (greater than 45 seconds) second phase. They were considered to be at risk of developing underwater hypoxia and unexpected loss of consciousness. It is further suggested that analysis of the phases of breath holding holds promise as a screening test of both novice and experienced divers.

Carbon Dioxide↗
PubMed1986

Arterial oxygenation and oxygen transport during exercise in patients with chronic obstructive pulmonary disease.

Twenty patients with chronic obstructive pulmonary disease (COPD) walked on the treadmill until symptoms limited further exercise. Ventilation, pulmonary gas exchange, arterial and mixed venous blood gas and haemodynamic variables were measured during steady state. It was not possible to predict from any resting cardiopulmonary variables (including static lung function tests) which patients would develop a decline in arterial PO2. In spite of variable PvO2 values at symptom-limited exercise, a good correlation was obtained between arterial haemoglobin saturation with oxygen and the venous admixture fraction. The directional change in PaO2, however, did not always follow that of the total oxygen transport to the tissues as gauged by either the PvO2 or the efficiency of oxygen delivery (oxygen flux/oxygen consumption) when expressed as a percentage of the value predicted for the level of exertion. This was due to the variable and unpredictable response of the cardiac output on exercise. It is concluded that there is a need to assess each patient individually both at rest and on exercise when evaluating arterial oxygenation and oxygen transport. The pattern of exercise-induced change in these oxygen indices is not predictable from resting data and they may even follow opposite directional trends.

Adult↗
PubMed1986

Cardiac output during exercise in patients with COPD.

Cardiac output response was examined to determine its relationship to exercise and arterial hypoxia, pulmonary hemodynamics, and the clinical/lung mechanics profile of patients with chronic obstructive pulmonary disease (COPD). Twenty patients with COPD were examined on the treadmill at rest and during steady state exercise at the highest workload comfortably tolerable to the subjects (60-70% VO2 max). In eight patients, the exercise cardiac output was less than 80% of predicted, while in the remainder (n = 12), the cardiac output response was normal (greater than 80% of predicted). It was concluded that hyperinflation and severe expiratory airflow limitation may be important determinants of the low exercise cardiac output response in some patients with COPD.

Aged↗
PubMed1986

Pulmonary function in young insulin-dependent diabetic subjects.

To clarify the issue of pulmonary dysfunction in diabetes mellitus, lung mechanics and CO transfer were investigated in 22 young (mean age 19.5 +/- 5 years) non-smoking, insulin-dependent diabetic patients and an equal number of matched healthy subjects. Mean closing capacity/total lung capacity (CC/TLC) was significantly greater in the diabetic than in the control group (31.4 +/- 6.8 vs 27.2 +/- 2.9 percent, p less than 0.01), as was the mean value of the volume independent index of lung elasticity (exponent constant, Kst(L)) (0.148 +/- 0.045 vs 0.118 +/- 0.030, p less than 0.05). The transfer factor expressed per unit alveolar volume (TL/VA) was also significantly lower in the diabetic than in the control group (5.25 +/- 0.68 vs 5.61 +/- 0.57 ml/min/mm Hg/L, p less than 0.05) and this could be ascribed to a lower pulmonary capillary blood volume. There was evidence of mildly abnormal lung mechanics and/or a decreased pulmonary capillary blood volume in 16 (73 percent) of the diabetic group. Since pulmonary dysfunction was either an isolated non-endocrine finding or was associated with only early systemic complications in these young patients, our findings suggest that pulmonary dysfunction is an early measurable complication in insulin-dependent diabetes mellitus.

Adolescent↗
PubMed1985

Ventilation during steady-state exercise in patients with chronic obstructive pulmonary disease. A preliminary study.

In this preliminary study 20 patients with chronic obstructive pulmonary disease (COPD) walked on the treadmill until symptoms limited further exercise. When minute volume exceeded 60% of the predicted maximum breathing capacity the arterial carbon dioxide partial pressure was frequently low, thus indicating hyperventilation; the arterial oxygen partial pressure also declined on exercise. In only 2 patients was there alveolar hypoventilation. Although other factors may be operative, the hyperventilation in some patients with COPD may be induced by an exertional decline in alveolar oxygen partial pressure. In 4 patients the exercise tidal volume exceeded the resting inspiratory capacity, indicating a decline in functional residual capacity and increased work of breathing. It is concluded that there is a need further to assess patients with COPD in respect of the association between exertional dyspnoea, alveolar ventilation and lung mechanics.

Aged↗
PubMed1985

Exercise in patients with chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) may incur exercise limitation by any one or combination of disturbances in breathing mechanics, oxygen transport, respiratory muscle metabolism or respiratory regulation and sensation. In spite of the increased ventilation demand/capacity ratio in these patients, the relationship between breathing mechanics, respiratory muscle fatigue, the adequacy of alveolar ventilation and the development of exertional dyspnoea is neither clearly defined nor predictable from data obtained with the patient at rest. The issue of oxygen transport during exercise has been complicated by confusion between arterial hypoxia and inadequate volume of oxygen transported to the tissues, which frequently may differ qualitatively and quantitatively. The cardiac output response to exercise in patients with COPD is therefore critical in determining oxygen transport. This response is also impossible to predict from resting lung mechanics, pulmonary arterial blood pressure, arterial oxygen tension or clinical disease profile. Without exercise testing, which includes measurement of all the variables mentioned, it is impossible to define clearly the cause of exercise-induced symptoms in patients with COPD. Exercise training with and without supplemental oxygen has been shown to improve exercise tolerance in these patients, but the precise mechanism of this improvement remains obscure.

Hemodynamics↗