Photoplethysmography

We are interested in the waveforms.

1. Pulsatile physiological waveform (AC, ~1Hz): cardiac synchronous changes
2. Slow varying baseline (DC): respiration, sympathetic nervous system activity, thermoregulation

The important factors are

1. blood volume,

2. blood vessel wall movement,

3. orientation of red blood cells (RBC),

4. absorption: ¹

   1. Optical water window: Absorbs ultraviolet and infrared; melanin also absorbs shorter wavelengths,
   2. Isobestic wavelength,
   3. Tissue penetration depth,

5. multi-bilateral site photoplethysmography

Pulse Wave

1. Pulse distortions and alterations at the periphery
2. Damage and disease in the vascular

References and Notes