The American review of respiratory disease
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Am. Rev. Respir. Dis. · Aug 1992
Exposure-response relationships between occupational exposures and chronic respiratory illness: a community-based study.
Data from a random sample of 3,606 adults 40 to 69 yr of age residing in Beijing, China, were analyzed to investigate the association of reported occupational exposures to dusts and gases/fumes with the prevalence of chronic respiratory symptoms and level of pulmonary function. The prevalence of occupational dust exposure was 32%, and gas or fume exposure, 19%. After we adjusted for age, sex, area of residence, smoking status, coal stove heating, and education, an increased prevalence of chronic phlegm and breathlessness was significantly related to both types of exposures. ⋯ Among subjects who did not report using coal stove heating, dust exposure was a significant predictor for FEV1, FEV1/FVC, FEF25-75, and peak expiratory flow rate (PEFR). There was also a significant decrease for FEV1 and FVC with increase of gas/fume exposure levels. Both current and former smokers appeared to be more susceptible to the effect of dusts than the never smokers.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Aug 1992
Perception of airway obstruction in a random population sample. Relationship to airway hyperresponsiveness in the absence of respiratory symptoms.
Subjects with asymptomatic airway hyperresponsiveness in epidemiologic studies may have variable airway obstruction that is not perceived as dyspnea. We tested the hypothesis that such subjects are less likely to report an increase in dyspnea during histamine-induced bronchoconstriction than symptomatic hyperresponders. A random population sample of 412 middle-aged subjects was studied. ⋯ The level of and increase in the Borg score were not significantly related to level and change in airway caliber (FEV1). In hyperresponsive subjects (PC10 < or = 16 mg/ml), subjects who reported dyspnea, wheeze, or asthma were more likely to show an increase in Borg score during histamine provocation than asymptomatic subjects (adjusted odds ratio 4.01, 95% confidence interval 1.01 to 16.00, p = 0.049), after adjustment for age, sex, smoking habits, FEV1, and atopy. This suggests that asymptomatic hyperresponders may have variable airway obstruction that is not recognized as breathlessness.
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Am. Rev. Respir. Dis. · Jul 1992
Effects of broxaterol and theophylline on fatigued canine diaphragm in vivo. A randomized, controlled study.
Since broxaterol, a new beta 2-agonist, has been shown to improve contractility of fatigued canine diaphragm in vitro, a controlled, randomized study was designed to assess its effects on fatigued canine diaphragm in vivo, and compare these to the expected inotropic effects of aminophylline. Diaphragm fatigue was induced in 21 dogs using electrophrenic stimulation at 20 Hz until transdiaphragmatic pressure (Pdi) at 20 Hz was reduced to about 50% of its original value. After stabilization of fatigue, animals were randomized in three groups. ⋯ In contrast, broxaterol administration resulted in a significant (p less than 0.05) and long-lasting increase in Pdi at low stimulation frequencies. Pdi at 20 Hz thus increased by 20 +/- 16% 90 min after the first bolus, and by 36 +/- 18% 90 min after the second dose. We conclude that (1) broxaterol promotes recovery of low-frequency fatigue in a dose-dependent way, and (2) theophylline does not improve the force output of fatigued canine diaphragm in vivo.
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Am. Rev. Respir. Dis. · Jun 1992
A model of airway narrowing in asthma and in chronic obstructive pulmonary disease.
We have examined the effect of airway wall thickening, loss of lung recoil, and airway smooth muscle shortening on the increase in airway resistance using a model of the human tracheobronchial tree. The values for airway wall thickening were determined morphometrically on the postmortem or surgically resected lungs of normal subjects, patients with moderate chronic obstructive pulmonary disease, and patients with severe asthma. Loss of recoil was simulated by deflating airways along their pressure-area curves by 1 to 3 cm H2O. ⋯ The analysis shows that moderate amounts of airway wall thickening, which have little effect on baseline resistance, can profoundly affect the airway narrowing caused by smooth muscle shortening--especially if the wall thickening is localized in peripheral airways. The combination of a loss of recoil and airway wall thickening are more than additive in their effect on simulated airway responsiveness. We conclude that airway wall thickening and a loss of lung recoil can partially explain the airway hyperresponsiveness observed in patients with chronic obstructive lung disease and asthma.
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Am. Rev. Respir. Dis. · Jun 1992
Effect of thyroid hormone on in vivo contractility of the canine diaphragm.
This study was designed to examine the effects of long-term (4 wk) administration of thyroid hormone on the in vivo contractility of the canine diaphragm. We implanted a pair of piezoelectric crystals chronically in the left crural and costal parts of the diaphragm by a midline laparotomy. Contractility was assessed by changes in the shortening of muscle fibers after twitch stimulation of both the crural and the costal parts of the diaphragm and in the transdiaphragmatic pressure (Pdi) after tetanic stimulation (10 to 100 Hz). ⋯ In the quadriceps femoris, although twitch force showed no change, both the maximal rate of contraction and maximal rate of relaxation became faster, and tetanic force decreased. Histologic examination of hyperthyroid dogs showed vacuolization and loss of fiber area of the diaphragm. These observations suggest that thyroid hormone impairs contractility of both the crural and costal parts of the diaphragm similarly, and that the decrease in contractility may be due to a loss of muscle mass and summation impairment of twitch contraction, which differs from that in other skeletal muscles.