Photoplethysmography in noninvasive blood pressure monitoring

Clinical management of hypertension and hypotension has been hindered by current cuff blood pressure (BP) measurement devices, which are not always readily available or continuous and can be disruptive to the user. Photoplethysmography (PPG) is a simple yet effective tool for tracking pulsatile arterial blood volume changes that can improve BP measurement. Volume clamping via finger cuff-PPG devices is a proven continuous method, whereas oscillometry via PPG-force sensor units, pulse transit time detected via PPG waveform(s), and PPG waveform feature extraction are potential cuff-less methods. The objective of this chapter is to facilitate the advancement of PPG-based BP monitoring. First, the clinical BP measurement methods and their limitations are explained. Then, the PPG principle and available sensors are reviewed. Next, the four PPG-based BP measurement methods are described including principles, embodiments, and empirical evidence. Finally, these methods are compared, future research directions are pinpointed, and a brief outlook on the approach is provided.