Due to the lack of specificity of symptoms, it is difficult to make a direct diagnosis of COPD. Instead, a physician will look for indicators that can indicate respiratory obstruction. Factors suggestive of COPD include:
- Progressive dyspnea: which gets worse with exercise.
- Chronic sputum production: Any pattern of sputum production is indicative of respiratory obstruction (COPD).
- History of exposure to etiologic agents.
- A family history of COPD.
Once this ‘checklist’ is verified and the possibility of COPD is highlighted, a more specific diagnostic approach is considered, which combines physical examinations, laboratory tests, and imaging techniques.
The physician looks for the “Hoover’s sign,” which involves analyzing the inward drawing of the ribcage during inspiration instead of outwards. This is indicative of a flattened diaphragm ,which contracts inwards due to hyper expanded muscles in the rib cage.
Barrel chest examination includes testing for hyper inflated lungs caused by obstruction of airways, leading to air being trapped inside the alveoli, thus reducing their elasticity and contributing to inflation. Inflation increases the anterior and posterior diameter of the chest (rib cage), giving it the shape of a barrel, hence the name. This is more indicative of emphysema, leading to wheezing during expiration, decreased and low-pitched breathing sounds, and prolonged expiration with coarse crackles.
Patients with chronic bronchitis upon physical examination produce cough and expectoration, rhonchi (coarse sounds, rales), and have rapid cardiac outputs.
Spirometric analysis, which measures the FEV and FVC (forced vital capacity: the total amount of air that can be exhaled during a single expiration), also helps in assessing COPD. The ratio of FEV/FVC, when falling below 70%, denotes a state of airflow obstruction that is not fully reversible.
Differential diagnosis of conditions with similar end-results, such as congestive heart failure, bronchiolitis, and bronchiectasis are also performed in order to rule out possibilities.
Additional tests that aid in confirming COPD include,
- Sputum culture: to check for bacterial infections (Hemophilus influenzae , Streptococcus pneumoniae, Pseudomonas aeruginosa, Moraxella catarrhalis, etc.). The sputum is also analyzed to check for macrophages and neutrophils.
- Metabolic alkalosis is checked as patients with COPD tend to retain high levels of sodium.
- Arterial blood gas analysis helps in detecting COPD when the FEV falls below 1l/s or 30% of the predicted value. A pH of less than 7.3 indicates respiratory compromise.
- Chest radiography helps in detecting chronic bronchitis and emphysema to some extent, with the former being marked by increased bronchovascular markings and cardiomegaly, and the latter being marked by bullous findings, a smaller heart and hyperinflated rib cage.