Spirometry: What does a spirometry tell my doctor?
Posted May 02 2009 11:33pm
If you’re slowing down due to shortness of breath, talk to your doctor. Get a simple breathing test. Learn more—breathe better.
Spirometry is a simple breathing test, that can be done in physician’s office that measures the amount of air you can blow out after you have taken in the deepest breath you can. The results of this test give two important numbers that measure airway obstruction.
> FVC: Forced Vital Capacity: the total volume of air you can forcefully blow out. It is an assessment of the size of your lungs, how well your lungs expand and contract, and how well the air passages open and close.
Patients with obstructive lung disease usually have a normal or only slightly decreased vital capacity. A Reduced FVC is associated with restrictive lung disorders, diseases that may be caused by inflammation or scarring of the lung tissue (interstitial lung disease) or by abnormalities of the muscles or skeleton of the chest wall.
> FEV1: Forced Expiratory Volume: is the volume of air that you can blow out in the first second of exhalation.
Typically FEV1 is considered “normal” if greater than 80% of predicted. FEV1 is reduced in both obstructive and restrictive lung disease.
> FEV1/FVC: This ratio compares the volume of air expelled in the first second to the total volume expelled.
In healthy patients the FEV1/FVC is usually around 70%-80%. In patients with obstructive lung disease FEV1/FVC decreases and can be as low as 20-30% in severe obstructive airway disease. Restrictive disorders have a near normal FEV1/FVC ratio.