An acute exacerbation of chronic obstructive pulmonary disease (COPD) can be mild, moderate and severe. Being a progressive disease, it generally is considered to have a poor prognosis and a high mortality rate.
An early diagnosis of a COPD exacerbation ensures an early treatment. This improves the prognosis and slows down the progression of the disease. The diagnostic criteria of an acute COPD exacerbation, therefore, attain immense importance in view of this vital fact.
Secondly, the patient should be a known and diagnosed case of COPD. The reason for this is that a COPD exacerbation can be confused with other conditions due to similar symptoms such as shortness of breath and treatments of these cases differs.
“An estimated three million people are affected by COPD in the UK. COPD is under-diagnosed. 60-85% of patients, mainly with mild-to-moderate disease, are thought to remain undiagnosed”.
COPD exacerbations differential diagnosis
The common health conditions that can be confused with a COPD exacerbation include:
- Congestive heart failure
- Pulmonary embolism
These conditions can also occur in patients with COPD as its complications. So, a confirmed diagnosis becomes essential for a quick recovery.
COPD exacerbation diagnosis and tests
The criteria for a medical diagnosis of an acute COPD exacerbation involves clinical assessment by the pulmonologist, lung function test (spirometry), a chest x-ray, sputum culture and specific diagnostic blood tests.
The patient should be above the age 35 to 40 years with a history of present or past smoking.
He should also present with the exacerbation symptoms such as increased frequency and severity of coughing with a change in color and thickness of the sputum, shortness of breath and wheezing. In an exacerbation due to an infective cause, fever with chills is often present.
A history of exposure to a known cause or a risk factor will help to narrow down the diagnosis.
Chest x- ray
A chest x-ray will help to rule out other conditions and narrow down the diagnosis of a COPD exacerbation. This may or may not be conclusive.
- Pulmonary embolism chest X-ray will show an elevation of the diaphragm often with slight atelectasis (partial collapse or incomplete inflation of the lung) and a small unilateral pleural effusion.
- Pneumonia chest X-ray will show lower lobe opacity with or without pleural effusion.
- Pneumonia chest X-ray will show a collapsed lung with air in the pleural space indicated by a black space.
- A chest X-ray of an asthma patient typically is not of much diagnostic importance.
- Chest X-ray in congestive heart failure will show an enlarged heart besides other signs.
The chest x-ray of a patient with acute COPD exacerbation will show an increased anteroposterior diameter, increased retrosternal airspace, flattening of the diaphragm, hyperinflation of the lungs, bullae, decreased lung markings, a narrow vertical heart and the presence or absence of comorbidity.
Chest CT scan
The doctor may order a chest CT if the chest x-ray findings are inconclusive.
Pulse oximetry will show hypoxemia — an abnormally low concentration of oxygen in the blood. This is done routinely outside the hospital.
Spirometry or the lung function tests will show the level of airflow obstruction and the stage of COPD.
A sputum gram stain and culture may be asked for in severe and infective cases to identify the responsible pathogen.
Arterial blood gas measurement (ABG)
ABG testing is done in patients with a moderate to severe acute exacerbation and will show:
- Hypercarbia — abnormally elevated carbon dioxide (CO2) levels in the blood
- Hypoxemia — an abnormally low concentration of oxygen in the blood.
- Respiratory acidosis also called respiratory failure or ventilatory failure is a condition wherein when the lungs cannot remove all of the carbon dioxide from the blood due to an impaired gas exchange. This causes the blood, to become too acidic
Complete blood count (CBC)
CBC will show
- Anemia — low hemoglobin count
- Polycythemia — a condition that results in an increased level of circulating red blood cells in the blood
- Leucocytosis – increase in the white blood cells if the exacerbation is due to an infective cause
Other blood tests that may be asked for include
- Renal function tests
- Serum electrolytes
Both these tests are usually normal in an uncomplicated case of COPD exacerbation.
Cardiac troponin test
The troponin test will rule out any heart muscle injury.
The doctor may order an ECG to rule out any cardiac comorbidity such as right ventricular hypertrophy, cardiac ischemia, and arrhythmias.