The Relationship of Chronic Obstructive Pulmonary Disease (COPD) to Asthma

Rhee, Yang Keun

Abstract

Chronic obstructive pulmonary disease (COPD) and bronchial asthma are considered to be two distinct respiratory symptoms that share a functional abnormality, namely, airflow limitation. The new diagnosis of both syndromes relies on the measurement of expiratory flow, in particular, the forced expiratory volume measured after first-second forced expiration (FEV1) from forced vital capacity (FVC). COPD is characterized by poorly reversible or irreversible airflow limitation, wheareas asthma is characterized by reversible airflow obstruction, but the definitions of the COPD and asthma overlap each other, and 10-30% of COPD patients are combined with asthma. COPD and asthma should be considered separately, given the increasing divergence in the overall approach to treatment. COPD is largely "irreversible" - in constrast to asthma - and not substantially improved by inhaled anti-inflammatory treatment. In most cases, the clinical presentations of COPD and asthma are relatively easy to distinguish and the key in differentiating between them is history taking, physical examination, sputum and bronchoalveolar lavage fluid (BALF) examination, bronchial provocation and bronchodilator response test, HRCT, and biopsy. However, in some cases, it is very difficult to distinguish between pure COPD and COPD combined with asthma. I suggest, in these cases, peak expiratory flow rate (PEFR) is very valuable to evaluate the diurnal and seasonal variations of lung function needed for differential diagnosis.