For example, your FEV1 could be 80% of your predicted value.

It may be done to assess symptoms before an asthma diagnosis has been made or to monitor asthma control.

There are a number of different models with different features and price points.

Man about to breath into a forced expiratory volume machine

Science Photo Library Collection / Brand X Pictures / Getty Images

Sharoon D, Edwards CW.Forced expiratory volume.

Updated September 14, 2020.