Pulmonary Function Test


Spirometry measures the amount of air entering and leaving the lungs. The technician performs this simple test using a computerized instrument. This machine measures airflow that passes through the machine. The patient inhales deeply and then completely exhales through the machine. This is a valuable screening test that can identify obstructive diseases (asthma, emphysema) or restrictive diseases (fibrosis).

Peak Flow Rate

The spirometer also measures peak expiratory flow rate (PEFR). The doctor compares these readings with readings the patient obtains at home with their own portable peak flow meter.

Postbronchodilator Spirometry

If the doctor suspects an obstruction, he may repeat spirometry after the administration of a bronchodilator. This procedure provides some information on the potential responsiveness of the airways to medication as can be seen in asthma.

Lung Volume

Lung volumes are measured by a gas dilution method using either nitrogen or helium. The most important measurements are residual volume (RV) and total lung capacity (TLC). A high total lung capacity demonstrates hyperinflation, which is is consistent with emphysema. A low total lung capacity suggests restrictive disease and is consistant with fibrosis among other problems. Increased residual volume indicates air trapping. These tests are very important in understanding the individual patient's problem and point the way to optimal therapy.