Spirometry

As part of the cardiac evaluation, a pulmonary technologist or respiratory therapist administers a spirometry test. For this test, the patient breathes into a device that measures lung volume and flow rates. Measured values are then compared with predicted values based upon the patient's sex, age and height.

The spirometry test is performed at least three times to obtain the best effort measurements. The patient is instructed to place their mouth tightly around the mouthpiece, with a nose clip in place, and inhale as much air as possible. The patient then forcefully exhales with maximum effort until their lungs are completely empty. When completely empty, the patient then quickly inhales until their lungs are full again.

An arterial blood gas sample is obtained to evaluate the ability of the lungs to get oxygen into the blood and dispose of carbon dioxide. Additional evaluation of lung gas exchange is performed while the patient breathes on a mouthpiece during exercise on a treadmill.