definition of copd

In 2004, the UK National Institute for Clinical Excellence
defined chronic obstructive pulmonary disease (COPD) as
“characterised by airflow obstruction. The airflow obstruction is
usually progressive, not fully reversible and does not change
markedly over several months. The disease is predominantly
caused by smoking.” COPD is the preferred umbrella term for
the airflow obstruction associated with the diseases of chronic
bronchitis and emphysema. These are closely related to, but not
synonymous with, COPD.
Although asthma is associated with airflow obstruction, it is
usually considered as a separate clinical entity. Some patients
with chronic asthma also develop airflow obstruction that is
relatively fixed (a consequence of airway remodelling) and often
indistinguishable from COPD. Because of the high prevalence
of asthma and COPD, these conditions coexist in many patients,
creating diagnostic uncertainty. Other conditions also associated
with poorly reversible airflow obstruction include cystic fibrosis,
bronchiectasis, and obliterative bronchiolitis. Although these
conditions need to be considered in the differential diagnosis of
obstructive airways disease, they are not conventionally covered
by the definition of COPD