Pulse Transit Time (PTT)

Pulse Transit Time (PTT) is the time it takes for a pulse wave generated by a heartbeat to travel between two arterial sites. It is closely related to Pulse Wave Velocity (PWV), which measures the speed of the pulse wave through the arterial system. PTT is inversely related to blood pressure: higher blood pressure results in stiffer arterial walls and faster pulse wave propagation, yielding shorter PTT.

In clinical research, PTT has been extensively studied as a potential method for continuous, cuffless blood pressure monitoring. The relationship between PTT and blood pressure is well-established physiologically, though individual calibration is typically needed for accurate absolute BP values. PTT-based approaches offer the possibility of more frequent BP monitoring without the discomfort and intermittent nature of cuff-based measurements.

Contactless blood pressure estimation using rPPG technology leverages PTT-related features extracted from facial video analysis. By analyzing the morphology and timing characteristics of the pulse wave signal detected through the camera, algorithms can estimate relative blood pressure changes and identify trends. While contactless PTT-based BP estimation is not yet a replacement for clinical cuff measurements, it enables screening and trend monitoring in telehealth and wellness applications.