What does peak flow testing measure and who primarily uses it?

• A. A test that measures blood oxygen saturation
• B. A quick test to measure air flowing out of the lungs; also called PEFR or PEF; mostly used by people with asthma
• C. A test of lung volumes during inhalation
• D. A test of diffusion capacity for carbon monoxide

Answer: (B)

Peak flow testing measures how fast air can be blown out of the lungs during a forceful exhale. The reading, called peak expiratory flow rate (PEFR or PEF), is a quick, simple way to monitor how open your airways are. It’s especially useful for people with asthma because it helps track changes in airway narrowing over time and informs treatment decisions through an asthma action plan. You perform a rapid, hard blow into a peak flow meter, which gives you a number you can compare to a personal best to assess control and know when to adjust medications or seek care.

This isn’t about oxygen levels in the blood, which is measured with a pulse oximeter. It isn’t a test of lung volumes during inhalation, which is what spirometry assesses for inspiratory capacity. And it isn’t a measure of how well gases diffuse from the lungs into the blood, which is the diffusion capacity test for carbon monoxide.