Table of Contents
Other findings may include:
- Breathlessness when the patient lies flat
- Increased pressure in the veins
Pulmonary Function Tests (Spirometry)
The best tests for diagnosing COPD and seeing how well it responds to treatment are pulmonary function tests. The gold-standard test for patients with respiratory symptoms such as shortness of breath is spirometry. Spirometry measures the volume and force of air as it is exhaled from the lungs. It measures airway obstruction, can identify COPD early, and the results are standardized so they are always consistent.
Because it is easy, reliable, and relatively inexpensive, spirometry is an effective method to help health professionals diagnose COPD early, when it is most treatable. However, spirometry is underused, which may be due to a lack of access and training, as well as cost and time constraints.
The patient is asked to breathe in and breathe out forcefully into an instrument. This is repeated several times. The force of the air is then measured. From the results, the physician determines two important values:
The forced vital capacity (FVC). FVC is the maximum volume of air that a patient can breathe out with force. It indicates lung size, elasticity, and how well the air passages open and close.
The forced expiratory volume in one second (FEV1). FEV1 is the maximum volume of air that a patient can breathe out in 1 second after breathing in fully. Airflow is considered to be limited if the forced breath out stays low over 1 second. People with COPD have a decline in FEV1 over time. FEV1 is measured as "percent of predicted:"
- Moderate COPD is an FEV1 50 - 80% of predicted.
- Severe COPD is an FEV1 30 - 50% of predicted.
- The ratio of FEV1 to FVC (FEV1/FVC) is less than 70% of normal, regardless of whether the patient has an FEV1 greater than 80% or less than 50%.
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Review Date: 04/10/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
