Changes in carbon monoxide transfer over 22 years in middle-aged men

COPD Diagnosis: Time for Disruption

Articulating a satisfactory definition of a disease is surprisingly difficult. Despite the alarming individual, societal and economic burden of chronic obstructive pulmonary disease (COPD), diagnosis is still largely based on a physiologically dominated disease conception, with spirometrically determined airflow limitation as a cardinal feature of the disease. The diagnostic inaccuracy and insensitivity of this physiological disease definition is reviewed considering scientific developments of imaging of the respiratory system in particular. Disease must be approached as a fluid concept in response to new scientific and medical discoveries, but labelling as well as mislabelling someone as diseased, will have enormous individual, social and financial implications. Nosology of COPD urgently needs to dynamically integrate more sensitive diagnostic procedures to detect the breadth of abnormalities early in the disease process. Integration of broader information for the identification of abnormalities in the respiratory system is a cornerstone for research models of underlying pathomechanisms to create a breakthrough in research.

Change in pulmonary diffusion capacity in a general population sample over 9 years

Rationale

Data on the change in diffusion capacity of the lung for carbon monoxide (DL_CO) over time are limited. We aimed to examine change in DL_CO (ΔDL_CO) over a 9-year period and its predictors.

Methods

A Norwegian community sample comprising 1,152 subjects aged 18–73 years was examined in 1987 and 1988. Of the 1,109 subjects still alive, 830 (75%) were re-examined in 1996/97. DL_CO was measured with the single breath-holding technique. Covariables recorded at baseline included sex, age, height, weight, smoking status, pack years, occupational exposure, educational level, and spirometry. Generalized estimating equations analyses were performed to examine relations between ΔDL_CO and the covariables.

Results

At baseline, mean [standard deviation (SD)] DL_CO was 10.8 (2.4) and 7.8 (1.6) mmol·min⁻¹·kPa⁻¹ in men and women, respectively. Mean (SD) ΔDL_CO was −0.24 (1.31) mmol·min⁻¹·kPa⁻¹. ΔDL_CO was negatively related to baseline age, DL_CO, current smoking, and pack years, and positively related to forced expiratory volume in 1 second (FEV₁) and weight. Sex, occupational exposure, and educational level were not related to ΔDL_CO.

Conclusions

In a community sample, more rapid decline in DL_CO during 9 years of observation time was related to higher age, baseline current smoking, more pack years, larger weight, and lower FEV₁.

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.

Progression parameters for emphysema: A clinical investigation

In patients with airflow limitation caused by cigarette smoking, lung density measured by computed tomography is strongly correlated with quantitative pathology scores of emphysema, but the ability of lung densitometry to detect progression of emphysema is disputed. We assessed the sensitivity of lung densitometry as a parameter of disease progression of emphysema in comparison to FEV(1) and gas transfer. At study baseline and after 30 months we measured computed tomography (CT)-derived lung density, spirometry and carbon monoxide diffusion coefficient in 144 patients with chronic obstructive pulmonary disease (COPD) in five different centers. Annual change in lung density was 1.31 g/L/year (CI 95%: -2.12 to -0.50 HU, p=0.0015, 39.5 mL/year (CI 95%: -100.0-21.0 mL, p=0.2) for FEV(1) (-39.5 mL) and 24.3 micromol/min/kPa/L/year for gas transfer (CI 95%: -61.0-12.5 micromol/min/kPa/L/year, p=0.2). Signal-to-noise ratio (mean change divided by standard error of the change) for the detection of annual change was 3.2 for lung densitometry, but 1.3 for both FEV(1) and gas diffusion. We conclude that detection of progression of emphysema was found to be 2.5-fold more sensitive using lung densitometry than by using currently recommended lung function parameters. Our results support CT scan as an efficacious test for novel drugs for emphysema.

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.

Effects on diffusing capacity and ventilation--perfusion relationships of budesonide inhalations for 2 months in chronic obstructive pulmonary disease (COPD)

Forced expiratory volumes are reduced in chronic obstructive pulmonary disease (COPD), mainly as a result of inflammatory and morphological changes in the small airways (with a diameter < 2 mm) and in the alveoli. However, it is difficult to detect minor changes in small airways by spirometry measurements. To study the effects on small airways of inhaled corticosteroids (ICS), 19 stable COPD patients were investigated; 15 were evaluated by ventilation-perfusion (V(A)/Q) relationships, assessed by the multiple inert gas elimination technique, and by diffusing capacity for carbon monoxide (DL(CO)), assessed by the single breath technique. Measurements were repeated after 2 months of budesonide inhalations (800 microg) twice daily. Before ICS treatment: mean forced expiratory volume in 1 sec (FEV1) as a percentage of predicted (% P) was 40.1 (+/- 16.0)%, DL(CO)% P was 45.7 (+/- 25.0)% and 6.0 (+/- 6.4)% of the ventilation was directed at high V(A)/Q areas. The mean of the V(A)/Q ratio for ventilation (V-mean) was 2.7 times higher than normal. After 2 months of ICS: the mean of DL(CO)% P increased by 8.6 (+/- 19.4)%, and FEV1/vital capacity decreased by 6.9 (+/- 11.3)%. Basal morning and ACTH-stimulated S-cortisol levels were significantly reduced. All the V(A)/Q relationships remained unchanged. In conclusion, a significant increase in diffusion capacity for carbon monoxide levels after treatment with corticosteroid inhalations for 2 months was shown, but no significant improvements were found in forced expiratory airflow, lung volumes, or V(A)/Q relationships.