Investigations in COPD
- Lung function tests which demonstrate:
- Increased total lung capacity
- FEV1/ FVC Ratio usually less than 70%, an “obstructive” picture. This is demonstrated in Spirometry. The volume of air blown out in one second is divided by the total amount of air blown out, until all air is expired. This is expressed as a percentage value and a value of less than 70% indicates COPD.
- Reduced gas transfer at alveolar level
- Chest x-rays/ CT Scans - These can be often normal, however an X- ray is useful in excluding other pathology (e.g. lung cancer). In moderate and severe disease there may be visible on x-ray over-inflated lungs and disorganisation of blood vessel markings with a narrow, long heart shadow and a low, flat diaphragm. There may be an abnormally increased chest diameter. Bullae (locally over-distended skin lesions usually to greater than 1 centimetre in size) may be visible.
- Blood tests – There may be an increase in the count of red blood cells, which is known as “polycythaemia”, as a result of low oxygenation.
- Arterial blood Gases –which demonstrate mild reduction in blood oxygen levels, and normal carbon dioxide levels.
- Heart Function Tests – Echocardiogram shows the function of the heart, and ECG will demonstrate changes of right heart strain or heart failure (cor pulmonale).
Additional investigations in Emphysema
- Alpha- Antitrypsin levels – This is important in emphysema; though it accounts for only around 2% of emphysema it accounts for severe emphysema at a young age and early death, especially in cigarette smokers.
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Amended April 2008
