Slope Transit Time (STT): A Pulse Transit Time Proxy requiring Only a Single Signal Fiducial Point

A novel pulse transit time proxy measurement, slope transit time (STT), is proposed in this letter. STT is based on geometrical considerations of the arriving photoplethysmographic cardiac waveform and its computation requires only the measurement of a single point on each cardiac beat arriving at the peripheral site. This novel transit time is explained conceptually and its implementation illustrated through its application to signals from respiratory effort, Muller maneuver, and obstructive sleep apnea trials.