Flow / Volume: Classic devices (Triflo type) where your breath lifts balls or a piston. Ideal for medical rehabilitation, post-operative recovery, and mild lung exercise.
Resistance: Devices that challenge the respiratory muscles with adjustable resistance (like weights for the lungs). Ideal for athletes, fitness, and increasing endurance.
Positive Pressure: Specialized medical devices (PEP / OPEP) that create small vibrations during exhalation. Designed exclusively for liquefying and easily clearing mucus.