The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Case Reports
Fatal ball-valve airway obstruction by an extensive blood clot during mechanical ventilation.
A ball-valve airway obstruction by a blood clot cast of almost the whole bronchial tree occurred in a small-cell lung cancer patient, who had been on mechanical ventilation for 9 days. Chest radiographs revealed overinflated lungs. ⋯ A postmortem extraction of the clot was performed with a rigid tube. This case is rare because of absence of severe haemoptysis and lung volume reduction.
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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
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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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.