Symptomatic smokers without COPD have physiological changes heralding the development of COPD

Background Chronic Obstructive Pulmonary Disease (COPD) is a major health problem, mainly due to cigarette smoking. Most studies in COPD are dedicated to fully developed COPD in older subjects, even though development of COPD may start soon after smoking initiation. Therefore, there is a need to diagnose this “early disease” by detecting the initial events responsible for ultimate development of COPD.

Methods Measurement of maximum mid expiratory flow between 25–75 of vital capacity (MMEF) in a routine spirometry, that detects small airways disease, was used to investigate if MMEF abnormalities in smokers without COPD (noCOPD) would relate to respiratory symptoms and identify smokers that might progress to COPD. For this purpose we studied 511 smokers, 302 COPD and 209 noCOPD, followed long term with spirometry including MMEF, CO diffusion capacity (DLCO), 6-minute walking test (6MWT), MRC Dyspnoea Scale, and COPD Assessment Test (CAT). Three spirometries V1,V2,V3 (5±2.5 and 10±4 years apart respectively from V1) were performed to assess functional decline and development of COPD.

Results 65% of noCOPD had an abnormal MMEF (<80%) and 38% an abnormal DLCO. NoCOPD with MMEF<80% performed worse in the 6MWT (p=0.01), were more dyspnoeic (p=0.01) and had higher prevalence of chronic bronchitis than noCOPD with MMEF>80% (p=0.04). 21% of noCOPD with MMEF<80%, and 2.7% with MMEF>80% developed COPD by V3 (p=0.0004).

Conclusions The MMEF, a functional test available in a routine spirometry, can detect early lung abnormalities and identify the subset of symptomatic smokers with pathologic changes that might lead to COPD.