By Lee Guion, MA, RRT, FAARC

Neurorespiratory Clinical Specialist

Pulmonary function tests (PFTs) measure lung muscle strength and overall function. Lung function should be assessed at each clinic visit as part of an overall disease management strategy. Test results are used to determine need for breathing assistance and supportive therapies. Each clinic visit gives you the opportunity to discuss implications of test results and treatment options with your physician and respiratory clinical specialist. In the outpatient clinic or office setting, portable spirometers are used.


A Spirometer is a lightweight, portable, and reliable microcomputer that measures, calculates, records and displays lung function test results.

Spirometry measures how well you move air out of your lungs. Measurement of lung volume, air flow, and time are recorded and displayed numerically and in a graph. Spirometry focuses primarily on 2 areas of lung function:

FVC (forced vital capacity) measures the amount of air you can exhale after a maximum inhalation (in liters).

FEV1 (forced expiratory volume) measures how much air you can forcibly exhale in one second (liters per second)

FEV1/FVC is the ratio of forced expiratory volume in one second (FEV1) compared to the forced vital capacity (FVC), expressed as a percentage (FEV1%). It is used to classify your results.

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