Mortality by level of emphysema and airway wall thickness.

RATIONALE: There is limited knowledge of the prognostic value of quantitative computed tomography (CT) measures of emphysema and airway wall thickness (AWT) on mortality. OBJECTIVES: To examine 8-year mortality in relation to CT-measured emphysema and AWT, and assess if potential impact of these predictors remained after adjustment for lung function. METHODS: In the Norwegian GenKOLS study of 2003-2005, 947 ever-smokers (49% with COPD) aged 40-85 years performed spirometry and CT examination. Mortality data from 2003-2011 were gathered from the Norwegian Cause of Death Registry. CT emphysema % low-attenuation areas (%LAA) and standardized measure for AWT (AWT-Pi10) were main predictors. We performed Laplace regression for survival data, estimating survival time for specified population percentiles within each emphysema category. Models were adjusted for sex, FEV1, COPD status, age, body mass index, smoking, and inflation level. MEASUREMENTS AND MAIN RESULTS: During 8-year follow-up all-cause mortality rate was 15%. Although 4% of the subjects with %LAA less than 3 died, 18% with %LAA 3-10 and 44% with %LAA greater than or equal to 10 died. After adjustment, the comparable percentile subjects with medium and high emphysema had 19 months shorter survival than subjects who died in the lowest emphysema category. Subjects with %LAA greater than or equal to 10 had 33 and 37 months shorter survival than the lowest emphysema category with regard to respiratory and cardiovascular mortality, respectively. No significant associations were found between %LAA and cancer and lung cancer mortality. AWT did not predict mortality independently, but a positive interaction with emphysema was observed. CONCLUSIONS: AWT affected mortality with increasing degree of emphysema, whereas CT measure of emphysema was a strong independent mortality predictor.

[Instructing patients in the correct use of inhalation devices]. / Opplaering av pasienter i riktig bruk av inhalasjonsmedisiner.

BACKGROUND: Limited knowledge is available on to what extent doctors and nurses know the correct use of various inhalation devices. We wanted to examine this skill among 25 doctors and 25 nurses randomly selected from the departments of pulmonology, internal medicine and surgery at a university hospital. DESIGN: Two technicians asked them to demonstrate the correct use of a metered-dose inhaler (MDI), Turbuhaler and Diskus. The performance was checked against a list of criteria with a maximum obtainable score of 9 for each device. RESULTS: The mean (SD) scores for the MDI, Turbuhaler and Diskus were 2.6 (2.0), 2.9 (2.2) and 3.7 (2.5), respectively. The score for the Diskus was significantly higher than those for the other two devices. The staff of the pulmonary department scored significantly higher than the staff of the other two departments, the scores for the pulmonary department being 4.1 (1.9), 4.8 (1.5) and 5.5 (1.5), respectively. The scores for the department of internal medicine were 2.4 (1.8), 2.7 (2.2) and 3.4 (2.5), and the scores for the department of surgery were 1.5 (1.2), 1.4 (1.5) and 2.3 (2.5). INTERPRETATION: This study indicates that there is a significant potential for improvement in correct use of these inhalation devices.

Diffusion capacity and CT measures of emphysema and airway wall thickness - relation to arterial oxygen tension in COPD patients.

BACKGROUND: Decreased diffusing capacity of the lung for carbon monoxide (DLCO) is associated with emphysema. DLCO is also related to decreased arterial oxygen tension (PaO2), but there are limited data on associations between PaO2 and computed tomography (CT) derived measures of emphysema and airway wall thickness. OBJECTIVE: To examine whether CT measures of emphysema and airway wall thickness are associated with level of arterial oxygen tension beyond that provided by measurements of diffusion capacity and spirometry. METHODS: The study sample consisted of 271 smoking or ex-smoking COPD patients from the Bergen COPD Cohort Study examined in 2007-2008. Emphysema was assessed as percent of low-attenuation areas<-950 Hounsfield units (%LAA), and airway wall thickness as standardised measure at an internal perimeter of 10 mm (AWT-Pi10). Multiple linear regression models were fitted with PaO2 as the outcome variable, and %LAA, AWT-Pi10, DLCO and carbon monoxide transfer coefficient (KCO) as main explanatory variables. The models were adjusted for sex, age, smoking status, and haemoglobin concentration, as well as forced expiratory volume in one second (FEV1). RESULTS: Sixty two per cent of the subjects were men, mean (SD) age was 64 (7) years, mean (SD) FEV1 in percent predicted was 50 (15)%, and mean PaO2 (SD) was 9.3 (1.1) kPa. The adjusted regression coefficient (CI) for PaO2 was -0.32 (-0.04-(-0.019)) per 10% increase in %LAA (p<0.01). When diffusion capacity and FEV1 were added to the model, respectively, the association lost its statistical significance. No relationship between airway wall thickness and PaO2 was found. CONCLUSION: CT assessment of airway wall thickness is not associated with arterial oxygen tension in COPD patients. Emphysema score measured by chest CT, is related to decreased PaO2, but cannot replace measurements of diffusion capacity in the clinical evaluation of hypoxaemia.

Case-control studies on risk factors for chronic obstructive pulmonary disease: how does the sampling of the cases and controls affect the results?

INTRODUCTION: Sampling is regarded as crucial to the validity of case-control studies. Ideally, cases and controls should be selected from the same source population, but deviations from this approach are often seen. OBJECTIVE: Our objective was to examine how exposure-disease relationships in a study on chronic obstructive pulmonary disease (COPD) were affected by the sampling sources of cases and controls. METHODS: A Norwegian case-control study on COPD including 1909 subjects used three sources of recruitment for cases (general population, hospital registry and volunteers) and two sources for controls (general population and volunteers). This resulted in six sampling combinations of cases and controls (groups A-F). We examined how the risk factors gender, age, smoking, educational level and comorbidity were associated with COPD in these six sampling groups. RESULTS: Several exposure-disease associations were dependent on variation in sampling source, thereby demonstrating the possibility of selection bias. The theoretically most ideal sampling group is likely group A, where both cases and controls are recruited from a general population. When using group A as a reference, the groups containing either voluntary controls and/or hospital-based cases deviated the most, suggesting higher susceptibility to selection bias in these groups. CONCLUSION: Recruitment from several sources made our study design vulnerable to selection bias. Our findings should bring about increased awareness to the sampling process, and encourage sampling of cases and controls from the same source population in future studies.