The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Comparative Study
Effects of lung volume and thoracic gas compression on maximal and partial flow-volume curves.
Comparing isovolume flows, measured at the mouth during forced expiratory manoeuvres as started from maximal or partial lung inflation, is a means of assessing the effects of deep inhalation on airway calibre. The aim of this study was to investigate whether the assessment of the effect of deep inhalation during induced bronchoconstriction is influenced by the lung volume at which it is determined and by volume differences due to thoracic gas compression that occur during forced expiratory manoeuvres. Four healthy subjects and six subjects with mild-to-moderate asthma subjects performed partial and maximal forced expiratory manoeuvres in a flow-type body plethysmograph at control and during a methacholine (MCh) inhalation challenge. ⋯ We conclude that during induced bronchoconstriction, the bronchodilation following a deep inhalation, expressed as maximal to partial flow ratio is dependent both on lung volume and volume differences due to thoracic gas compression. The use of expired flow and volume measurements may lead to a small but systematic overestimation of the bronchodilator effect of a deep inhalation. On the contrary, maximal to partial flow slope is insensitive either to lung volume or volume differences due to thoracic gas compression and can, therefore, be fairly determined from expired flow-volume loops.
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The aim of this study was to determine the current incidence of side-effects severe enough to cause intolerance of standard antituberculosis therapy with isoniazid, rifampin and pyrazinamide in patients hospitalized as a result of pulmonary tuberculosis. Five hundred and nineteen patients with proven pulmonary tuberculosis, who initially received standard antituberculosis therapy, were retrospectively studied in the department of infectious diseases in a teaching chest hospital. The incidence of severe side-effects related to the therapy, which led to the definitive termination of one of the three standard drugs, was measured and the risk factors for intolerance were analysed. ⋯ Significant risk factors for intolerance of the standard therapy following a multivariate analysis were a history of hepatitis (odds ratio (OR) 3.4; 95% confidence interval (95% CI) 1.6-7.6; p = 0.0026) and an age > or = 60 yrs (OR 1.9; 95% CI 1.2-3.2; p = 0.017). Both of these risk factors were also significantly associated with the intolerance of pyrazinamide (history of hepatitis: OR 2.5; 95% CI 1.4-4.3; p = 0.0045; age > or = 60 yrs: OR 2.1, 95% CI 1.3-3.5; p = 0.0029) but not of isoniazid and rifampin. The side-effects of standard antituberculosis therapy are frequent in hospitalized patients aged > or = 60 yrs or with a history of previous hepatitis, and are probably due to pyrazinamide rather than to isoniazid or rifampin.
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Review Comparative Study
Control of breathing in mechanically ventilated patients.
During mechanical ventilation, the respiratory system is under the influence of two pumps, the ventilator pump and the patient's own respiratory muscles. Depending on the mode of mechanical ventilatory support, ventilation may be totally controlled by the ventilator or may be determined by the interaction between patient respiratory effort and ventilator function. In either case, compared to spontaneous breathing, the breathing pattern is altered and this may influence: 1) force-length and force-velocity relationships of respiratory muscles (mechanical feedback); 2) chemical stimuli (chemical feedback); 3) the activity of various receptors located in the respiratory tract, lung and chest wall (reflex feedback); and 4) behavioural response (behavioural feedback). ⋯ Thus, the response of ventilator to patient effort, and that of patient effort to ventilator-delivered breath are inevitably the two components of control of breathing during mechanical ventilation; the ventilatory output is the final expression of the interaction between these two components. As a result of this interaction, the various aspects of control of breathing of the respiratory system may be masked or modulated by mechanical ventilation, depending on several factors related both to patient and ventilator. This should be taken into consideration in the management of mechanically ventilated patients.
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Comparative Study
A five year follow-up of lung function among chemical workers using flow-volume and impedance measurements.
Impedance of the respiratory system, measured using the forced oscillation technique (FOT), has repeatedly been proposed as a tool for occupational health screening. The aim of this study was to compare the outcome of impedance measurements and flow-volume curves, and to study relationships between lung function decline and specific exposures and smoking. Both measurements were applied in 136 chemical workers from seven main production/personnel groups during a 5 year follow-up (1990-1995). ⋯ Smoking had a significant effect on most flow-volume parameters but only for frequency dependence among the impedance outcomes. It is concluded that alterations in impedance parameters do reflect changes in flow-volume curves induced by age. smoking and occupational exposure. Therefore, these data are a valuable extension to current cross-sectional data.
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Comparative Study
Glucocorticoid resistant asthma: T-lymphocyte steroid metabolism and sensitivity to glucocorticoids and immunosuppressive agents.
We have previously shown that T-lymphocytes from clinically glucocorticoid (GC) resistant asthmatics are more refractory to dexamethasone suppression in vitro than those of GC sensitive asthmatics. We wished to extend these observations to compare three GCs used topically for asthma therapy (budesonide, beclomethasone dipropionate and fluticasone 17 alpha-propionate) and three immunosuppressive drugs (cyclosporin A, FK506 (tacrolimus) and mycophenolate mofetil) with dexamethasone for their antiproliferative effects on T-lymphocytes from GC sensitive and resistant asthmatics, and also to compare the rates of steroid metabolism by T-lymphocytes from these patients. Antiproliferative activity of the drugs was measured on peripheral blood T-lymphocytes activated with phytohaemagglutinin (PHA) and anti-CD3 antibody in vitro. ⋯ The rates of total metabolism and 20 alpha-hydroxylation of steroid by homogenates of T-lymphocytes from GC sensitive and resistant asthmatics were equivalent. Thus, relative GC resistance in T-lymphocytes from GC resistant as compared with sensitive asthmatics is: 1) manifest with GC molecules of variable molecular structure; 2) not accompanied by elevated intracellular metabolism of steroids; and 3) overcome by immunosuppressive drugs which inhibit T-lymphocytes by non-GC-mediated mechanisms. We conclude that current anti-asthma glucocorticoids at therapeutic concentrations are unlikely to be of benefit for the therapy of glucocorticoid resistant asthma, and that other immunosuppressive drugs may have potential as therapeutic agents in these patients.