Predicted values for the forced expiratory flow adjusted for forced vital capacity, a descriptive study

BACKGROUND

The forced expiratory flows (FEFs) towards the end of the expiration may be more sensitive in detecting peripheral airways obstruction compared to the forced expiratory volume in 1 s and forced vital capacity (FVC). However, they are highly variable. A partial solution is to adjust the FEFs for FVC (FEF/FVC). Here we provide reference equations for these adjusted FEFs at 25%, 50%, 75% and 25-75% of FVC, which are currently lacking.

METHODS

We included pulmonary healthy, never-smoker adults; 14 472 subjects from Lifelines, a biobank for health research, and 338 subjects from the department's control cohorts (NORM and Fiddle). Reference equations were obtained by linear regression on 80% of the Lifelines dataset and validated on the remaining data. The best model was defined as the one with the highest adjusted R2-value. The difference in variability between adjusted and unadjusted FEFs was evaluated using the coefficient of variation.

RESULTS

For all adjusted FEFs, the best model contained age, height and weight. The adjustment improved the coefficient of variation of the FEF75 from 39% to 36% and from 43% to 40%, respectively, in males and females. The highest percentage of explained variance by the reference equation was obtained for FEF75/FVC, 32%-38% for males, and 41%-46% for females, depending on the validation set.

CONCLUSION

We developed reference equations for FVC-adjusted FEF values. We demonstrated minimally yet significantly improved variability. Future studies in obstructive airway diseases should demonstrate whether it is worthwhile to use these (predicted) adjusted FEF values.

Airway inflammation in COPD after long-term withdrawal of inhaled corticosteroids

Long-term treatment with inhaled corticosteroids (ICS) might attenuate lung function decline and decrease airway inflammation in a subset of patients with chronic obstructive pulmonary disease (COPD), and discontinuing ICS treatment could result in further lung function decline. We hypothesised that airway inflammation increases after ICS withdrawal following long-term ICS treatment in COPD.

In the GLUCOLD-1 study (GL1), 114 patients with moderate-severe COPD were randomised to 6-month or 30-month treatment with fluticasone propionate (500 µg twice daily), 30-month treatment with fluticasone/salmeterol (500/50 µg twice daily) or placebo. During the 5-year follow-up study (GL2), patients were followed prospectively while being treated by their physician. Bronchial biopsies and induced sputum were collected at baseline, at 30 months (end of GL1) and at 7.5 years (end of GL2) to assess inflammatory cell counts. Data were analysed using linear mixed-effects models.

In patients using ICS during GL1 and using ICS 0–50% of the time during GL2 (n=61/85), there were significant increases in GL2 bronchial CD3+ (fold change per year calculated as GL2 minus GL1 2.68, 95% CI 1.87–3.84), CD4+ (1.91, 95% CI 1.33–2.75) and CD8+ cells (1.71, 95% CI 1.15–2.53), and mast cells (1.91, 95% CI 1.36–2.68). The sputum total cell counts increased significantly in GL2 (1.90, 95% CI 1.42–2.54), as did counts of macrophages (2.10, 95% CI 1.55–2.86), neutrophils (1.92, 95% CI 1.39–2.65) and lymphocytes (2.01, 95% CI 1.46–2.78).

ICS discontinuation increases airway inflammation in patients with moderate-severe COPD, suggesting that the anti-inflammatory effects of ICS in COPD are not maintained after ICS discontinuation.