PEFR/FEV1: Peak Expiratory Flow Rate/Forced Expiratory Volume in 1 Second

What does PEFR/FEV1 mean? The above is one of PEFR/FEV1 meanings. It may have other definitions. Please refer to the end of this passage.

Definition in English: Peak Expiratory Flow Rate/Forced Expiratory Volume in 1 Second