Photoplethysmogram
（重定向自Photoplethysmography）
![Representative PPG taken from an ear pulse oximeter. Variation in amplitude are from Respiratory Induced Variation.](/Images/godic/202502/02/PPG2505.PNG")
![Diagram of the layers of human skin](/Images/godic/202502/02/Skin2505.png")
![Premature Ventricular Contraction (PVC) can be seen in the PPG just as in the EKG and the Blood Pressure (BP).](/Images/godic/202502/02/PVC_detectionUsing_PGG2505.png")
![Venous pulsations can be clearly seen in this PPG.](/Images/godic/202502/02/VenousPulsationAnd_PGG2505.png")
A photoplethysmogram (PPG) is an optically obtained plethysmogram, a volumetric measurement of an organ. A PPG is often obtained by using a pulse oximeter which illuminates the skin and measures changes in light absorption. A conventional pulse oximeter monitors the perfusion of blood to the dermis and subcutaneous tissue of the skin.