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Tests and Procedures

Pulmonary Function Tests

There are a variety of tests that can help a pulmonologist determine whether lung function is improving or declining.


The FEV1, FVC and the FEV1/FVC ratio are lung volumes that can be obtained from spirometry. Spirometry is a procedure that is performed by forcibly emptying all of the air from the lungs after taking a deep breath to maximal lung capacity. The volumes are defined below.

  • FEV1(Forced Expiratory Volume for 1 sec) = Volume of air exhaled during an forced exhalation in the first second
  • FVC (Forced Vital Capacity) = The total volume of air exhaled during a rapid forced exhalation starting from full inspiration
  • FEV1/FVC ratio = volume of air exhaled in the first second of an forced exhalation maneuver expressed as a percent to FVC.

The maneuvers are typically repeated several times to ensure there is consistency between the efforts. The values obtained are compared to expected values that are age, height, sex and race matched, as these variables all significantly affect lung volumes. Patients with pulmonary fibrosis may have a reduction in both the FEV1 and FVC. A decline in FVC has been used as a marker of fibrosis progression in many of the IPF clinical trials.

Diffusing Capacity

The diffusing capacity is an estimate of how well oxygen can move from the lung into the blood stream. This test is performed using a single breath hold technique.