The UCLA population studies of chronic obstructive respiratory disease. 5. Agreement and disagreement of tests in identifying abnormal lung function

Spirometric indices of early airflow impairment in individuals at risk of developing COPD: Spirometry beyond FEV1/FVC

Spirometry is the current gold standard for diagnosing and monitoring the progression of Chronic Obstructive Pulmonary Disease (COPD). However, many current and former smokers who do not meet established spirometric criteria for the diagnosis of this disease have symptoms and clinical courses similar to those with diagnosed COPD. Large longitudinal observational studies following individuals at risk of developing COPD offer us additional insight into spirometric patterns of disease development and progression. Analysis of forced expiratory maneuver changes over time may allow us to better understand early changes predictive of progressive disease. This review discusses the theoretical ability of spirometry to capture fine pathophysiologic changes in early airway disease, highlights the shortcomings of current diagnostic criteria, and reviews existing evidence for spirometric measures which may be used to better detect early airflow impairment.

The Contribution of Small Airway Obstruction to the Pathogenesis of Chronic Obstructive Pulmonary Disease

The hypothesis that the small conducting airways were the major site of obstruction to airflow in normal lungs was introduced by Rohrer in 1915 and prevailed until Weibel introduced a quantitative method of studying lung anatomy in 1963. Green repeated Rohrer's calculations using Weibels new data in 1965 and found that the smaller conducting airways offered very little resistance to airflow. This conflict was resolved by seminal experiments conducted by Macklem and Mead in 1967, which confirmed that a small proportion of the total lower airways resistance is attributable to small airways <2 mm in diameter. Shortly thereafter, Hogg, Macklem, and Thurlbeck used this technique to show that small airways become the major site of obstruction in lungs affected by emphysema. These and other observations led Mead to write a seminal editorial in 1970 that postulated the small airways are a silent zone within normal lungs where disease can accumulate over many years without being noticed. This review provides a progress report since the 1970s on methods for detecting chronic obstructive pulmonary disease, the structural nature of small airways' disease, and the cellular and molecular mechanisms that are thought to underlie its pathogenesis.

Biomarkers in migraine: their promise, problems, and practical applications

Biomarkers are physical signs or laboratory measurements that "occur in association with a pathological process and have putative diagnostic and/or prognostic utility." Biomarkers hold considerable promise for understanding and intervening in the disease process of migraine. They may permit recognition of individuals at risk of developing migraine, improve the timing, accuracy, and precision of migraine diagnosis, and serve as indicators of treatment response and disease progression. Furthermore, they hold great promise for research. At the same time, there are important limitations to the use of biomarkers in migraine, including problems with validity, reliability, accuracy, and precision. Legal, ethical, and cost considerations are also important. This review describes the potential uses and limitations of biomarkers in migraine diagnosis, treatment, and research.

Choosing optimal values of FEV1 and FEV1/FVC for surveillance for respiratory disorders in occupational populations

Pulmonary lung-function testing plays an important role in surveillance programs for occupational respiratory disorders. Spirometry is usually utilized by applying preset cut-off values to discriminate between healthy and unhealthy subjects. This article demonstrates the usefulness of decision analysis techniques to arrive at an optimal diagnosis. The diagnostic performance of FEV1 and FEV1/FVC was evaluated by relative operating characteristics curves (ROCs) applied to data of a cohort gathered in 1965. Both parameters showed quite similar ROCs, with a maximal sensitivity of 40% at a specificity of 95% relative to the physician's diagnosis of respiratory disorder. The area under the curves was. 75 for both FEV1 and FEV1/FVC, illustrating that misclassification of 25% of the subjects is likely to occur. Regarding the consequences of a false-positive and a false-negative decision as of equal importance, the 5%-percentile (FEV1 residual less than -1.2 L) would be the optimal cut-off. An FEV1 residual below the lower 5%-percentile was six times more likely to appear in subjects with chronic nonspecific lung disease (CNSLD) than in subjects without. The post-test probability of CNSLD was three to four times the pre-test probability. In occupational or public health practice, however, false-positive results need to be avoided, even at the expense of a higher false-negative rate. In those situations, a more rigid cut-off between normal and abnormal values may be warranted.

Marijuana smoking, pulmonary function, and lung macrophage oxidant release

Pulmonary alveolar macrophages lavaged from tobacco smokers release increased levels of oxidants and have been implicated in the pathophysiology of emphysema. It is unknown whether lung macrophages recovered from marijuana smokers also liberate excessive levels of oxidants. To evaluate this possibility, pulmonary alveolar macrophages were obtained by bronchoalveolar lavage from nonsmokers, smokers of marijuana only, smokers of tobacco only, and smokers of tobacco plus marijuana. Spontaneous and stimulated superoxide anion release was measured by the superoxide dismutase-inhibitable reduction of ferricytochrome c. These findings were correlated with recent lung function tests. Superoxide anion production by macrophages, studies of small airway integrity (closing volume, closing capacity, and the slope of Phase III of the single-breath nitrogen washout curve), and evaluation of alveolar gas exchange (diffusing capacity of carbon monoxide) were similar in both nonsmokers and marijuana smokers. However, tobacco smoking was associated with both significantly higher levels of superoxide anion release by pulmonary alveolar macrophages and significant abnormalities of small airway function and alveolar diffusing capacity. Based on the results of this study, pulmonary alveolar macrophages of marijuana-only smokers do not produce increased amounts of oxidants when compared to macrophages of non-smoking subjects. This observation may account for the absence of abnormalities in small airway function and alveolar diffusing capacity in marijuana-only smokers, in contrast to the presence of such findings in smokers of tobacco, regardless of marijuana use.

Carbon monoxide diffusing capacity, other indices of lung function, and respiratory symptoms in a general population sample

To assess the relationships among single-breath diffusing capacity for CO (DLCOsb) (13), respiratory symptoms, and cigarette smoking in a general population sample, the data of 718 men and 894 women 20 yr of age or older were analyzed, and comparisons were performed with flow-volume curve (MEFV) variables and the slope of the alveolar plateau (DN2%/L) as well. Percent predicted DLCOsb and its correction for alveolar volume (DL/VA) were significantly lower in smokers than in nonsmokers. The relationship of presence/absence of respiratory symptoms and cigarette smoking with DLCOsb and DL/VA was significant. DLCO indices were almost always selected as discriminant variables in multivariate analysis between asymptomatic and symptomatic subjects. Poor concordance among lung function tests was evident: in men, 30% with abnormal (i.e., lower than 97.5% percentile) and 21% with normal DLCO indices also had abnormal MEFV parameters and/or DN2%/L. In women, the corresponding figures were 24 and 10%, respectively. In men, when considering only DLCO indices, the percentage of symptomatic subjects with abnormal lung function tests ranged from 33% in those with at least one symptom to 45% in those complaining of dyspnea. When the proportion of symptomatic subjects with DN2%/L and MEFV abnormalities were added, it increased to 56 and 66%, respectively. However, in women the proportion of symptomatic subjects with abnormal lung function indices was very small. These results indicate the usefulness of including CO diffusing capacity in epidemiologic surveys in the detection of abnormalities.

Single breath nitrogen test in an epidemiologic survey in North Italy. Reliability, reference values and relationships with symptoms

The usefulness of single breath nitrogen test (SBN2) was evaluated in a cross-sectional epidemiologic survey on a general population sample (n = 3,289) of North Italy. Each subject was submitted to CNR standardized questionnaire and to lung function testing using automated equipment (Hewlett-Packard 47804S). Acceptable closing volume (CV) and slope of alveolar plateau (DN2%/L) tracings were performed by only 1,370 and 1,982 subjects respectively, in comparison with the 2,638 diffusing capacity and the 3,079 forced vital capacity acceptable maneuvers. Prediction equations were computed on normal subjects for CV indices, with the exception of DN2%/L: they were similar to those found in other studies. Significant differences among smoking categories were found for all the SBN2 parameters in males, but only for DN2%/L in females. The latter was also able to distinguish either subjects with airway obstruction from those without it or symptomatic from asymptomatic individuals, but DN2%/L did not give more information than Vmax75, a sensitive index of flow volume curve. Our results suggest that the place of SBN2 in large scale epidemiologic testing has not been justified.

Tracheobronchial changes in habitual, heavy smokers of marijuana with and without tobacco

We performed flexible fiberoptic bronchoscopy in 29 habitual, heavy marijuana smokers 25 to 45 yr of age, with and without concomitant tobacco smoking, to inspect and biopsy their proximal tracheobronchial tree for the evaluation of histopathologic changes. Control tobacco smokers (TS) and nonsmokers (NS) residing in the same metropolitan area were similarly studied and compared with the marijuana smokers (MS) and marijuana-tobacco smokers (MTS). Respiratory and drug histories, physical examination, and pulmonary function tests were obtained prior to bronchoscopy. The prevalence of respiratory symptoms and pulmonary function abnormalities was generally higher in the 3 smoking groups than in the NS group but was not statistically different across all groups. However, bronchoscopic inspection revealed airway hyperemia and other visible abnormalities in 32 (91%) subjects in the 3 smoking groups, unlike the unremarkable findings in the NS group. Light microscopy showed 2 or more histopathologic changes in the bronchial epithelium of all MS, MTS, and TS. Squamous metaplasia was observed in all MTS, a prevalence that was significantly different from that in MS, TS, and NS. Hyperplasia of basal and goblet cells was more prevalent in the MS than in the NS, whereas cellular disorganization was more prevalent in the MS than in the TS. A direct relationship between cumulative marijuana use (joint-years) and bronchoscopic and histopathologic changes was not apparent in this study sample. These results indicate that relatively young, habitual, heavy marijuana smokers have a high prevalence of abnormal airway appearance and histologic findings, irrespective of concomitant tobacco smoking.(ABSTRACT TRUNCATED AT 250 WORDS)

Small airways function in nonsmokers with rheumatoid arthritis

To evaluate the possible relationship between rheumatoid arthritis (RA) and airways dysfunction independent of cigarette smoking, we studied 19 lifetime nonsmokers with RA and 47 healthy nonsmokers. Ten tests of small airways function were administered to the subjects. In addition, diffusing capacity and static lung compliance were measured, and upstream airway conductance at mid-to-low lung volumes was calculated. Mean values were not significantly lower in the RA group than in the control group in any of the tests of small airways function. Three of the 19 (16%) patients with RA versus 15 of the 47 (32%) control subjects had abnormal findings on greater than 2 tests of small airways function (P greater than 0.1). Although mean diffusing capacity and static lung compliance were both within normal limits in each group, the former tended to be lower, while the latter was significantly lower, in the RA subjects. We conclude that airways dysfunction in RA, if present, is probably related to factors other than the underlying disease; if an association between RA and small airways abnormality is present in some patients, its prevalence is too small to have been detected in our sample.