Early emphysema. Ten years' evolution

Systematic review of the evidence relating FEV1 decline to giving up smoking

BACKGROUND

The rate of forced expiratory volume in 1 second (FEV1) decline ("beta") is a marker of chronic obstructive pulmonary disease risk. The reduction in beta after quitting smoking is an upper limit for the reduction achievable from switching to novel nicotine delivery products. We review available evidence to estimate this reduction and quantify the relationship of smoking to beta.

METHODS

Studies were identified, in healthy individuals or patients with respiratory disease, that provided data on beta over at least 2 years of follow-up, separately for those who gave up smoking and other smoking groups. Publications to June 2010 were considered. Independent beta estimates were derived for four main smoking groups: never smokers, ex-smokers (before baseline), quitters (during follow-up) and continuing smokers. Unweighted and inverse variance-weighted regression analyses compared betas in the smoking groups, and in continuing smokers by amount smoked, and estimated whether beta or beta differences between smoking groups varied by age, sex and other factors.

RESULTS

Forty-seven studies had relevant data, 28 for both sexes and 19 for males. Sixteen studies started before 1970. Mean follow-up was 11 years. On the basis of weighted analysis of 303 betas for the four smoking groups, never smokers had a beta 10.8 mL/yr (95% confidence interval (CI), 8.9 to 12.8) less than continuing smokers. Betas for ex-smokers were 12.4 mL/yr (95% CI, 10.1 to 14.7) less than for continuing smokers, and for quitters, 8.5 mL/yr (95% CI, 5.6 to 11.4) less. These betas were similar to that for never smokers. In continuing smokers, beta increased 0.33 mL/yr per cigarette/day. Beta differences between continuing smokers and those who gave up were greater in patients with respiratory disease or with reduced baseline lung function, but were not clearly related to age or sex.

CONCLUSION

The available data have numerous limitations, but clearly show that continuing smokers have a beta that is dose-related and over 10 mL/yr greater than in never smokers, ex-smokers or quitters. The greater decline in those with respiratory disease or reduced lung function is consistent with some smokers having a more rapid rate of FEV1 decline. These results help in designing studies comparing continuing smokers of conventional cigarettes and switchers to novel products.

Evolution of changes in carbon monoxide transfer factor in men with chronic obstructive pulmonary disease

Progression of chronic obstructive pulmonary disease (COPD) has been studied predominantly by following change in forced expiratory volume in 1s (FEV1) which reflects both primary airway disease and associated alveolar disease. Carbon monoxide transfer (Tlco) (the product of the transfer coefficient Kco and alveolar volume Va) is the only simple, widely available test of alveolar function, but few studies have followed long-term changes in an individual. Seventeen middle-aged men with moderate chronic airflow obstruction (mean FEV1 56% of predicted values) were observed with yearly measurements of FEV1, Tlco and Kco over a mean of 18.9 yr. At the end of follow-up FEV1 had fallen to 29% of predicted values. Va, measured by single breath dilution, fell in each man. Kco at recruitment ranged from 41% to 110% predicted and remained >75% predicted in eight men at the end of follow-up supporting a phenotype of COPD with predominant airway disease and little emphysema. Fall in FEV1 was faster (2.03% predicted FEV1/yr) in seven men with low initial Kco<75% pred. than in men with initial Kco>75% pred. (1.14% predicted FEV1/yr, P=0.006). Repeated measurements of CO transfer in an individual should increase the present poor knowledge of the contribution of alveolar disease to the progression of chronic airflow obstruction.

Functional alterations accompanying a rapid decline in ventilatory function

In a study of two groups of healthy males matched for age, smoking habits, and duration of follow-up, but differing in the rapidity of decline of FEV1 and/or vital capacity (VC), we measured lung volumes before and after bronchodilator inhalation, forced expiratory flows, diffusion capacity for CO (DLCO), and total respiratory impedance. A discriminant analysis showed that the separation between the two groups was achieved best by DLCO, weight, and FEV1/VC among the smokers and by body height and DLCO among the nonsmokers. The fact that DLCO turns out to discriminate between people with a rapid and a normal spirographic decline in the present group points to the possibility of using this measurement, in combination with FEV1/VC and weight, as a predictor of rapid decline of lung function in middle-aged healthy male smokers.

Measurement of lung density by means of quantitative CT scanning. A study of correlations with pulmonary function tests

In recent years, much attention has been given to the role of CT in detecting and quantitating pulmonary emphysema. We measured CT lung density in 45 patients undergoing a diagnostic work-up and compared this with pulmonary function tests. The CT lung densities measured with the sector method and with the whole lung method were very highly correlated with each other (r = 0.96, p less than 0.001), and measurements at TLC systematically gave a lower density than those at FRC (p less than 0.001). Also, CT density measurements at TLC and even more so at FRC correlated well with pulmonary function indices of airway obstruction and of hyperinflation, but not with indices that are considered more specific for emphysema (single breath DCO, static lung compliance) We conclude that CT lung-density gives a good reflection of the degree of hyperinflation, ie, enlargement of distal airways, but is not sensitive to detect whether or not this is associated with emphysema.

Total respiratory resistance and reactance in patients with asthma, chronic bronchitis, and emphysema

A comparison was made of total respiratory resistance (Rrs) and reactance (Xrs) determined between 6 and 26 Hz by means of a forced oscillation technique in 27 patients with asthma (group A), 28 patients with chronic bronchitis (group B), and 20 patients with emphysema (group E) to examine whether the method can provide data capable of distinguishing among these diseases. The three groups demonstrated a similar reduction in the FEV1. In addition, static and dynamic lung volumes, maximal expiratory flows, diffusing capacity for CO, airway resistance (Raw), and elastic lung recoil were measured. The observed alterations of Rrs and Xrs consisted of an increase in Rrs, a decrease in Rrs with frequency, and a decrease in Xrs. However, significant differences were found between the three groups: Rrs at 6 Hz and average Rrs were most increased in group A, whereas the negative frequency dependence of Rrs and the decrease in Xrs were least pronounced in group E. In all groups Rrs at 6 Hz, the average slope of Rrs, and the average level of Xrs were tightly interrelated and showed in addition a high correlation with airway resistance; the correlations with FEV1 were less satisfactory. Discriminant analysis performed on the complete set of data, excluding diffusing capacity and elastic lung recoil, which were used as selection criteria, demonstrated that forced oscillation parameters were the most important factors discriminating among the groups.

Comparison of dynamic lung function indices during forced and quiet breathing in upper airway obstruction, asthma, and emphysema

We compared the dynamic lung function indices in patients with asthma (n = 27), emphysema (n = 20), and UAO (n = 18), with the purpose being to examine whether different patterns of abnormalities could be found and which tests were most discriminative among the three groups. Forced expiratory indices were measured (FEV1; PEF; MEF50%), as well as indices obtained during quiet breathing (Raw; Gaw; Gaw/VL). The three groups were comparable as far as PEF was concerned (about 60 +/- 20 percent of predicted, yet the group with UAO showed significantly larger FEV1 (84 percent of predicted vs 55 percent and 57 percent of predicted in asthma and emphysema respectively), and larger MEF50% (71 percent of predicted vs 25 percent and 23 percent of predicted in the other groups), and the group with asthma had the largest Raw (0.37 +/- 0.18 kPa.s.L-1 vs 0.24 +/- 0.13 in UAO and 0.22 +/- 0.10 in emphysema). From these functional tests, several ratios were derived which were discriminative among the three groups. Upper airway obstruction could be recognized by a significantly lower PEF/MEF50% ratio and higher FEV1/PEF ratio than in the other conditions. Furthermore, a distinction between asthma and emphysema could be made by comparing airway patency during forced and quiet breathing, ie, the MEF50%/Gaw ratio. This ratio was, in fact, significantly different for all three groups, having the lowest value in emphysema (0.19 +/- 0.08 kPa vs 0.44 +/- 0.23 kPa and 0.63 +/- 0.34 kPa in asthma and UAO, respectively). Within the group with UAO, those with variable intrathoracic obstruction showed the least difference from asthma and emphysema for the measured indices.

Pulmonary function in middle-aged women with heterozygous deficiency of the serine protease inhibitor alpha 1-antichymotrypsin

Heterozygous alpha 1-antichymotrypsin (ACT) deficiency is inherited in an autosomal dominant mode independently of alpha 1-antitrypsin with a gene frequency (q) of 0.003. In a previous study, a high prevalence of enlarged residual volumes in subjects with the trait were noted. Neutrophil cathepsin G, the target proteinase of ACT, enhances the elastolytic action of elastase. Thus, hypothetically, subjects with the trait may have increased risk for developing pulmonary emphysema. To test whether heterozygous ACT deficiency predisposes to lung disease, plasma ACT concentrations were determined in a cohort of 1,872 middle-aged women. Women with subnormal levels were studied with respect to heredity, airway symptoms, and lung function. Twelve women (0.64% of the cohort) were classified as heterozygotes after family studies and were compared with control subjects, matched for age, weight, sex, and smoking status. There were no significant differences in airway symptoms between heterozygotes and control subjects. However, the prevalence of ex-smokers was significantly higher among heterozygotes than among the screened population as a whole (prevalence ratio, 2.18; 95% confidence interval, 1.004-4.72). There were no differences between the heterozygotes and the control subjects in the basal spirometry. However, after bronchodilation, five of the 12 heterozygotes manifested residual volumes greater than 2.5 standard deviations above normal mean compared with one of 24 control subjects (p = 0.012). The present investigation thus confirms our previous findings of an increased prevalence of enlarged residual volumes in heterozygous ACT deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Emphysematous change in chronic asthma in relation to cigarette smoking. Assessment by computed tomography

To evaluate the occurrence and the degree of emphysema in chronic asthma in relation to the effect of cigarette smoking, we examined 35 subjects with irreversible airway obstruction (17 nonsmokers and 18 smokers). We performed pulmonary function testing and CT scans on all subjects. The ES was assessed by a visual scoring system on CT scans. Between nonsmokers and smokers, there was a significant difference in the ES (p less than 0.05), but not in the FEV1, TLC, and Dsb/VA (expressed as percent predicted values). The ES was 2.3 +/- 4.7 percent (mean +/- SD) in nonsmoking subjects and 13.7 +/- 16.7 percent in smoking subjects. In all subjects the ES showed significant correlations with Dsb/VA (p less than 0.001) and pack-years of cigarette consumption (p less than 0.001) but did not show correlations with FEV1 and with TLC. We concluded that emphysema can occur in smoking asthmatic subjects because of the effect of cigarette smoking, and CT scans are useful for detecting this emphysematous change.