Grouped Perfusion Parameter

A single Perfusion slider that adjusts Pleth Amplitude, Pleth Morphology, and Pleth PTT together along realistic physiological curves, with a toggle to decouple for advanced scenarios. In v1 the three pleth controls are independently adjustable - ideal for power users. The Perfusion grouped parameter is the long-term direction for instructor ease-of-use, allowing a single drag from Normal to Severe Shock with all three parameters adjusting together realistically. A decouple toggle lets instructors break out of grouped mode for advanced or atypical scenarios. Should only be built after the three independent v1 controls have been validated.