American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Oct 1994
Comparative StudyAntigen-specific stimulation of histamine releasing factors in diisocyanate-induced occupational asthma.
Diisocyanate-induced asthma differs from occupational asthma (OA) caused by protein allergens in that specific IgE antibody responses are rarely identified. To investigate the immunopathogenesis of diisocyanate asthma, diisocyanate-exposed workers were evaluated for in vitro production of antigen-specific mononuclear cell-derived histamine releasing factor (HRF). The mean HRF response to diisocyanate-HSA antigens was significantly greater in patients with OA than in diisocyanate-exposed asymptomatic subjects (p < 0.05). ⋯ Analysis of HRF production by subpopulations of peripheral blood mononuclear cells (PBMC) showed that lymphocytes and adherent cells were major sources of both spontaneous and antigen-stimulated HRF. The results suggest that antigen-specific HRF produced by PBMCs are an important biomarker for diisocyanate-induced asthma. This is the first report of hapten-specific stimulation of PBMCs resulting in HRF production.
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Am. J. Respir. Crit. Care Med. · Oct 1994
Randomized Controlled Trial Comparative Study Clinical TrialComparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation.
Several modalities of ventilatory support have been proposed to gradually withdraw patients from mechanical ventilation, but their respective effects on the outcome of weaning from mechanical ventilation are not known. We conducted a randomized trial in three intensive care units in mechanically ventilated patients who met standard weaning criteria. Those who could not sustain 2 h of spontaneous breathing were randomly assigned to be weaned with T-piece trials, with synchronized intermittent mandatory ventilation (SIMV), or with pressure support ventilation (PSV). ⋯ The three groups were comparable in terms of etiology of disease or characteristics at entry in the study. When all causes for weaning failure were considered, a lower number of failures was found with PSV than with the other two modes, with the difference just reaching the level of significance (23% for PSV, 43% for T piece, 42% for SIMV; p = 0.05). After excluding patients whose weaning was terminated for complications unrelated to the weaning process, the difference became highly significant (8% for PSV versus 33% and 39%, p < 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Oct 1994
Comparative StudyHyperpnea limits the volume recruited by positive end-expiratory pressure.
The effectiveness of positive end-expiratory pressure (PEEP) relates directly to alveolar recruitment. We tested the hypothesis that active use of expiratory muscles during labored breathing impairs the ability of PEEP to increase end-expiratory lung volume. ⋯ Hyperpnea also shifted the distribution of the recruited volume toward regions sampled by the rib cage band of the plethysmograph. Whatever advantage expiratory muscle activity may have for minimizing the workload of the inspiratory muscles, the cost may be reduced effectiveness of PEEP in increasing lung volume and improving oxygen exchange.
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Am. J. Respir. Crit. Care Med. · Oct 1994
Comparative StudyNicotine prevents a reduction in neutrophil filterability induced by cigarette smoke exposure.
Decreased deformability of neutrophils exposed to cigarette smoke is considered a determinant of neutrophil sequestration within the pulmonary microvasculature, which may be a risk for the development of pulmonary emphysema. In this study we examined the effect of nicotine, a major cigarette component, on the reduction in neutrophil deformability, measured as cell filterability, after exposed to cigarette smoke. Neutrophils were exposed to smoke by incubating them in an aqueous solution of smoke extracts. ⋯ Addition of nicotine, glutathione, alpha-tocopherol, thymol, and erythrocytes prevented the increase in membrane resistance following gas-phase smoke exposure. Nicotine also protected against an increase in membrane resistance against the effect of chloramine-T and hydrogen peroxide, but it provided no protection from superoxide radical generated from a xanthine-xanthine oxidase mixture of N-formylmethionylleucylphenylalanine. These results suggest that nicotine prevents the reduction in neutrophil filterability, probably by scavenging oxidants present in the cigarette smoke.