« Back to Glossary IndexBreathing trainers that use Passive Flow Resistance, use a simple dial to select holes of different sizes, to inspire or expire through. This results in a breathing load that is unreliable and cannot be accurately quantified. Passive Flow Resistance is not to be confused with Dynamically Adjusted Flow Resistance used in the electronic POWERbreathe K-Series and KH-Series of breathing trainers, which has none of the limitations inherent in passive flow resistance devices. This is because they use real-time, dynamic adjustment to breathing load, which changes the inspiratory challenge according to the user’s current breathing strength. « Back to Glossary Index