Question

Describe the values found in a pulmonary function test. Define these terms and give the relations to each other.

Answer 1

Pulmonary Function Test is an important technique to test and monitor the respiratory pathology of individuals. It gives information related to large and small airways, the size and integrity of pulmonary capillary bed and pulmonary parenchyma. PFTs measures how well the lungs are functioning.

Normal or predicted ranges of values are obtained from large population studies of healthy subjects. Values are taken for people matched for age, height, gender and where appropriate ethnicity.

If a value is abnormal, it means there is problem in lung function.

Slow Vital Capacity (SVC) is the maximum volume of air which can be exhaled or inspired in a slow/steady maneuver.

Vital Capacity (VC) is the largest of the volumes from either a forced (FVC) or a slow (SVC) maneuver.

Expiratory Reserve Volume (ERV) is the maximum volume of additional air that can be expired from the end of a normal expiration.

The results of PFT tests are characterized into:

• normal lung function
• obstructive disease
• or restrictive disease

In obstructive lung disease, patients have decreased airflow (decreased FEV1/FVC ratio) and usually have normal or above-normal lung volumes.

In restrictive lung disease, patients have decreased lung volumes or TLC with normal airflow (normal FEV1/FVC ratio but with reduced values for both FVC and FEV1 individually).