Correlation between differential spirometry and radiographic and gammagraphic methods.
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The persisting defects after treatment of tuberculosis in 51 patients were evaluated by a simultaneous measurement of the functional residual capacity (FRC) using the body plethysmograph and the helium dilution method. In most patients large volumes of trapped air were detected by the difference of two methods of measurement. The amount of trapped air showed to be dependent of the other pulmonary parameters obtained: Tiffeneau index, FRC measured by body plethysmography, difference between predicted and measured FRC.
Static and dynamic spirometric tests were performed in 21 healthy subjects (21-61 years old, 8 smokers and 9 ex-smokers) on 3 different days within 2 weeks. The design of the study allowed separation of the influence of learning and diurnal changes between 09.00 and 17.00 h. In addition, the reproducibility of the tests and the effect of inhalation of 2.5 mg of terbutaline sulphate were studied. No learning effect was observed. There were slight, but statistically significant differences between morning, noon and afternoon measurements. Thus, the residual volume and flow in the early phase of forced expiration were highest in the afternoon, while maximal voluntary ventilation was lower at noon than in the afternoon or morning. The intraindividual variabilities (defined as standard deviation of difference between first and second measurement) of total lung capacity, vital capacity and forced expiratory volume in 1 s (FEV1) were about 3% of the predicted values. The ratio of intra- to interindividual variability was 0.2-0.3. The remaining tests showed higher variability and a higher intra- to interindividual variability ratio. Terbutaline inhalation caused a significant increase in most forced expiratory flow variables. A 10% increase in FEV1 corresponded to a 50-60% increase in endexpiratory flow. In spite of this, the endexpiratory flow and mean transit time were better discriminators of the effects of bronchodilation in normal subjects.
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According to a previously published theoretical model of emphysema, the ratio of RV to TLC (RV/TLC) reflects the size mismatch between the hyperinflated lungs in the disease and the surrounding chest. The model suggests that RV/TLC is an important predictor of improvement in FVC and that increased FVC is an important determinant of increased FEV(1) after lung volume reduction surgery (LVRS). We tested these predictions in 13 patients undergoing LVRS, in whom we made detailed measurements of lung mechanics. Using stepwise regression, we found that RV/TLC was the only preoperative independent predictor of the increase in FVC. Seventy percent of the increase in FEV(1) was attributable to increased FVC, with the remainder due to increased FEV(1)/FVC. In a separate group of 78 LVRS patients evaluated with standard preoperative pulmonary function tests, RV/TLC again was found to correlate with the increase in FVC, and changes in FEV(1) were also due largely to changes in FVC. However, RV/TLC was not predictive of the increase in FEV(1) among the group of 78 patients, because FEV(1)/FVC in patients with a low preoperative RV/TLC often increased despite little change in FVC. These findings support the proposed mechanism for increased FVC following LVRS. They also illustrate the limitations of the model, and suggest further hypotheses for selecting patients who may benefit from surgery.
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Quantitative test criteria have been developed to assess the acceptability of spirometric tracings. Most automated spirometers have been programmed with the criteria in order to assist in data collection. These instruments compare computed parameters from the collected tracings with the criteria and, after 3 acceptable FVC maneuvers have been collected, print out a statement indicating that "tests meet acceptability criteria." Technicians, nurses, and even their medical supervisors are beginning to rely on these statements as assuring overall test quality. However, a review of actual curves indicates that unacceptable results can be obtained from tests that comply with these standards. Although quantitative test criteria are a positive step toward quality assurance, they should be treated as they were developed, as "minimum" criteria. All curves should be inspected for visible defects, especially if the results are used to follow subjects longitudinally.
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The relationship between 6 chronic respiratory symptoms and the performance of an excessively variable FEV1 (test failure) was examined among 8,522 white adults in 6 U.S. cities. A total of 747 (8.9%) performed an excessively variable FEV1 according to the American Thoracic Society criterion. After adjusting for smoking, age, and city of residence in 6 separate logistic regression models, the odds ratios for FEV1 failure among men were 2.32, 1.39, 1.40, 1.82, 2.61, 1.92 for moderate breathlessness, chronic cough, phlegm, wheeze, asthma, and recurrent chest illness, respectively. Among women, FEV1 failure was significantly associated with moderate breathlessness, chronic phlegm, wheeze, and asthma with odds ratios of 1.55, 1.45, 1.62, and 1.95, respectively. When all symptoms were evaluated simultaneously in a single logistic regression model, only breathlessness and asthma remained associated with FEV1 failure; odds ratio = 1.97 for asthma and 2.03 for breathlessness among men and 1.53 for both asthma and breathlessness among women. The 11-yr mortality experience of subjects with test failure, as defined by 2 different criteria, was compared to that of the quartile of the cohort with the highest cross-sectional test results. After adjusting for age, gender, and smoking, the relative risks of mortality were 1.62 and 1.98 for subjects with an FEV1 failure as defined by the ATS and 6-Cities criteria, respectively, and 1.99 and 1.90 for the groups with FVC failure as defined by the 2 criteria. Thus test failure is almost as strong a predictor of mortality as poor FEV1.
Thirty-one workers with occupational asthma caused by snow-crab processing were assessed by a long-term follow-up on three occasions at mean +/- SD intervals of 12.8 +/- 5.4, 31.4 +/- 6.3, and 64.4 +/- 6.3 months after leaving work. The diagnosis of work-related asthma was initially confirmed in all of them by specific inhalation challenges at the workplace or by laboratory inhalation of snow-crab boiling water (n = 24) or by serial monitoring of airway caliber and bronchial responsiveness to histamine at work and off work (n = 7). Total duration of work-related exposure was 12.8 +/- 5.6 months (range, 3 to 21 months), and the duration of symptoms after onset was 6.8 +/- 4.2 months (range, 1 to 18 months). At the time of diagnosis, all 31 subjects required medication for asthma, 11 had a FEV1 less than or equal to 85% predicted, and all subjects had a PC20 less than or equal to 16 mg/ml. Twelve of 25 serum samples assessed showed high levels of specific immunoglobulin E (IgE) antibodies to crab meat and/or boiling water. At the time of the first follow-up, there was a reduction in the number of subjects still requiring medication, with a significant reduction in FEV1, and a PC20 less than or equal to 16 mg/ml. However, no further change was observed afterwards. Similarly, the mean FEV1 and FEV1/FVC improved significantly from the time of diagnosis to the first follow-up (p less than 0.01), with a plateau thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of passive tobacco smoke exposure upon respiratory symptoms and lung function were assessed in a cross-sectional survey of 770 children 7 yr of age, using cotinine as a quantitative biochemical marker of exposure. Salivary cotinine levels were strongly related to the number of smokers in the home, but three-quarters of children from nonsmoking households had detectable salivary cotinine, and 10% of this group were in the upper two-fifths of the distribution of measured tobacco smoke exposure. Smoking by persons other than members of the household may deserve greater attention in future studies of young children. After adjustment for housing tenure, most respiratory symptoms were unrelated to salivary cotinine, but a "tendency for colds to go to the chest" was twice as prevalent in the upper two-fifths as in the lower two-fifths of the cotinine distribution. No association was found between salivary cotinine and reports of wheeze or measured reduction in FEV1 after 6 min of free running. After adjustment for sex, height, test conditions, and housing tenure, all baseline spirometric indices except FVC were inversely associated with salivary cotinine. Only FEF75-85 and FEF75 were significantly reduced, the difference for each index between the top and bottom quintiles of the cotinine distribution being about 7%, equivalent to a reduction of 1.1% (95% CL, 0.1 to 2.1%) per doubling of cotinine concentration. These changes may be evidence of small airways damage, which could later progress to more severe respiratory impairment.