Detrended fluctuation analysis of peak expiratory flow and exacerbation frequency in COPD

作者：Donaldson Gavin C^*; Seemungal Terence A R; Hurst John R; Wedzicha Jadwiga A

来源：European Respiratory Journal, 2012, 40(5): 1123-1129.

DOI：10.1183/09031936.00180811

• Anti-cholinergic agent
• chronic obstructive pulmonary disease
• detrended fluctuation analysis
• exacerbations
• peak expiratory flow

We investigated whether exacerbation frequency in chronic obstructive pulmonary disease (COPD) was related to an exponent alpha which quantifies self-similarity in daily peak expiratory flow (PEF) and is calculated using detrended fluctuation analysis (DFA).
We examined data from COPD patients who recorded an increase in respiratory symptoms and post-bronchodilator PEF on daily diary cards. We also investigated PEF data from a double-blind, placebo-controlled trial of the anti-cholinergic agent, tiotropium.
In the observational study there were 308 patients with COPD (195 males; mean +/- SD age 68.3 +/- 8.4 yrs, forced expiratory volume in 1 s (FEV1) 1.12 +/- 0.46 L, FEV1 % predicted 44.5 +/- 16.4%). The mean +/- SD alpha over the first year was 0.944 +/- 0.19 and it was positively related to the frequency of exacerbations per year (p=0.009). In the clinical trial, a was lower in COPD patients randomised to tiotropium, mean +/- SD 0.87 +/- 0.21 (n=48) than on placebo, mean +/- SD 0.95 +/- 0.19 (n=52; p=0.035). Power analysis showed that fewer patients would be required for clinical studies with a as the outcome measure than exacerbation frequency.
DFA shows that daily PEF in COPD has long-term correlations which are related to exacerbation frequency. Monitoring of PEF and use of a may result in smaller COPD patient sample sizes in trials.

• 出版日期2012-11