Is Pulse Transit Time a good indicator of Blood Pressure changes during short physical exercise in a young population?

The Pulse Transit Time (PTT) is generally assumed to be a good surrogate measure to comfortably track blood pressure (BP) and blood pressure changes. This paper investigates PTT variations for healthy young subjects during a sequence of short-term physical exercises. PTT was measured by two different methodologies having different measurement accuracies as well as underlying assumptions: the total PTT from heart to fingertip and the difference of fingertip and earlobe PTTs. Small non consistent changes and very low correlation of both PTTs with systolic blood pressure (SBP) have been observed for the study population (-0.19 +/- 0.45 and 0.22 +/- 0.46). In conclusion, there might be a need for an improved measurement accuracy of the sensors and data processing techniques in use. The applicability of the Moens-Korteweg equation is also questionable for young people having flexible arteries. In this case, significant radius changes do occur in the large arteries during exercise, which might counteract a PTT decrease with the BP elevation. These radius effects are excluded from the Moens-Korteweg model.