Forced Expiratory Volume and Forced Vital Capacity readings
Forced Expiratory Volume (FEV1)
This is the volume of air expired into a spirometer in the first second.
In COPD, the following values are indicative of the severity of the disease.
|
Mild disease |
Males – 2.5 litres or more |
| Females – 2.0 litres or more | |
|
Moderate disease |
Males – 1.5 litres to 2.49 litres |
| Females – 1.0 litres to 1.99 litres | |
|
Severe disease |
Males – less than 1.5 litres |
| Females – less than 1.0 litre |
FEV1 and Functional restriction table
This table shows the predicted FEV1 as a percentage figure and the likely level of corresponding functional restrictions.
Gradation of severity of airflow obstruction
| FEV1 (% predicted) |
Severity of airflow obstruction (Post-bronchodilator) |
|---|---|
| ≥ 80% | Stage 1 – Mild |
| 50–79% | Stage 2 – Moderate |
| 30–49% | Stage 3 – Severe |
| < 30% | Stage 4 – Very severe* |
*Or FEV1 < 50% with respiratory failure.
[Adapted from updated NICE Guidance 2010]
Please note that FEV1 % predicted while indicative is not a perfect predictor of level of disability.
Forced Vital Capacity (FVC)
This is the total volume of air breathed out by the person after a full inspiration (breath in) into a spirometer. This is not generally used as a diagnostic test in COPD.
The FEV1 / FVC Ratio
This is a useful diagnostic aid and is a measure of airflow limitation.
Normally, the FEV1 / FVC ratio is approximately 75%.
A value of below 70% is indicative of airflow obstruction (obstructive airways disease). This could be either asthma or COPD. The difference is that asthma is reversed when a short-acting beta agonist such as salbutamol or terbutaline are used (this is known as reversibility), whereas COPD is not reversible.
A value of between 70% and 75% is indicative of restrictive lung disease such as lung fibrosis, asbestosis etc.
Amended April 2011
