Lyapunov Estimation

Waveform-based PPG Lyapunov estimation still lacks validation against clinical outcomes. Moderate Lyapunov cross-modal correlation is attributed partly to estimation noise. Production deployment should treat waveform-derived maximum Lyapunov estimates as research-grade rather than primary clinical signals. Rosenstein Lyapunov estimation assumes stationarity during the estimation window, but cardiac signals vary even over short intervals. Short-window PPG Lyapunov estimation is near the lower reliability boundary for low attractor dimensions and undersampled for higher dimensions.