American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Oct 1994
Randomized Controlled Trial Multicenter Study Comparative Study Clinical TrialGender difference in airway hyperresponsiveness in smokers with mild COPD. The Lung Health Study.
Methacholine bronchoprovocation challenge testing was successfully completed in 5,662 participants (3,556 men and 2,106 women) at the time they were randomized into the Lung Health Study, a multicenter trial designed to evaluate early intervention in chronic obstructive pulmonary disease (COPD). All participants were smokers between the ages of 35 and 60 yr who had mild COPD. The male:female prevalence of a positive challenge (PC20FEV1) was 25%:48% and 63%:87% at a PC20FEV1 of < or = 5 mg/ml (AHR5) and < or = 25 mg/ml (AHR25), respectively. ⋯ When the measured baseline FEV1 was added to the model as a surrogate for airway caliber, the RR for female gender decreased to 1.06 (0.96, 1.18). Thus, in this population of middle-aged smokers with mild COPD, the high prevalence of AHR appears to be associated with a decrease in airway caliber. The higher prevalence of AHR noted in women is due to their having a smaller airway caliber than their male counterparts.
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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 StudyFish consumption may limit the damage of smoking on the lung.
High fish consumption is characteristic of Japanese-American men of the Honolulu Heart Program (HHP). Analyses of data from the Atherosclerosis Risk in Communities (ARIC) study suggest high fish intake protects the lung against smoking damage. Measurements of forced expiratory volume in 1 s (FEV1) and smoking status in the HHP cohort were done at the first examination in 1965-68. ⋯ However, the predicted FEV1 at < or = 30 cigarettes/d was 52 ml (95% CI: 17, 87) higher in the high fish consumption group. No significant difference in FEV1 was noted between groups at > 30 cigarettes/d. These findings suggest that the protective role of fish is "saturated" at higher "doses" of cigarette smoking.
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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.
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Am. J. Respir. Crit. Care Med. · Sep 1994
Comparative StudyUse of flow-volume curves in detecting secretions in ventilator-dependent patients.
A noninvasive means of detecting airway secretions in ventilator-dependent patients is desirable because endotracheal suctioning can result in life-threatening complications. In a patient who had copious secretions, we observed a sawtooth pattern on his flow-volume curve that disappeared after suctioning. Accordingly, we systematically examined the usefulness of a sawtooth pattern on flow-volume curves in detecting secretions in ventilator-dependent patients and compared its accuracy with clinical examination. ⋯ Interobserver agreement, assessed by the kappa statistic, was excellent: 0.76, 0.76, and 0.84. In the subgroup of patients evaluated by both clinical examination and flow-volume curve analysis, clinical examination was less accurate in 11 of the 15 patients. In conclusion, detection of a sawtooth pattern strongly suggests the presence of secretions, and the absence of this pattern suggests that secretions are unlikely to be present.