Record barometer values?

I am implementing a feature that can detect user’s movement such as Jumping or squatting, using Expo Barometer . Therefore I need to record the initial value of the air pressure when user first open the App.

For example, once user open the App, the initial value of the air pressure is 100, if user decide to jump, the air pressure will be decrease, by that I can compare with the initial air pressure to claim that the user just jump.

However I can’t find a way to record the values of the air pressure, Anyone knows? Any suggestion will be appreciated.
