- Vital capacity (VC), the maximum volume of air that can be inhaled or exhaled.
- Peak expiratory flow rate (PEFR), commonly called the peak flow rate, the maximum flow rate that can be generated during a forced exhalation.
- Forced expiratory volume (FEV1), the maximum volume of air expired in one second.
Spirometry is a painless study of air volume and flow rate within the lungs. Spirometry is frequently used to evaluate lung function in people with obstructive or restrictive lung diseases such as asthma or cystic fibrosis.
If the airways are obstructed, these measurements will fall. Depending on the results, the doctor will take the following steps:
- If measurements fall, the doctor typically asks the patient to inhale a bronchodilator medication. This drug is used in asthma to open the air passages. The measurements are taken again. If the measurements are more normal, the drug likely has cleared the airways and a diagnosis of asthma is likely.
- If measurement results fail to show airway obstruction, but asthma is still suspected, the doctor may perform a challenge test. This involves administering a specific drug (histamine or methacholine) that usually increases airway resistance only when asthma is present.
Allergy Tests
The patient may receive skin or blood allergy tests, particularly if a specific allergen is suspected and available for testing. Allergy skin tests may help diagnose allergic asthma, although they are not recommended for people with year-round asthma.
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Click the icon to see an image of allergy testing. |
Review Date: 05/03/2011
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)
