Which statement is NOT a characteristic of a normal plethysmography waveform?

• A. Absence of a dicrotic notch
• B. Prolonged downstroke with dicrotic notch 1/2 way down
• C. Sharp upstroke during peak systole
• D. Amplitude greater in fingers than toes

Answer: (A)

In a normal plethysmography waveform, you expect a brisk upstroke as arterial volume increases with each heartbeat, followed by a dicrotic notch on the downstroke that marks brief aortic valve closure and a small secondary deflection from wave reflections. The waveform then settles back toward baseline, and the overall amplitude is typically greater in well-perfused digits such as the fingers compared with the toes. Seeing a dicrotic notch is a typical feature; its absence would indicate something atypical about the signal or perfusion. Therefore, stating that there is an absence of a dicrotic notch is not a characteristic of a normal waveform. The other features described—a sharp upstroke during peak systole, a dicrotic notch appearing somewhere on the downstroke, and larger amplitude in fingers than toes—are consistent with normal plethysmography signals.