The acute effects of running on blood pressure estimation using pulse transit time in normotensive subjects.

Pulse transit time (PTT) is a potential parameter for cuffless blood pressure (BP) estimation. Since exercise induces changes in arterial properties that can influence the relationship between BP and PTT, we investigate whether PTT can be used to estimate BP after successive bouts of exercise. PTT-foot, PTT-peak (time intervals from the peak of electrocardiogram R-wave to the foot and peak of photoplethysmogram, respectively) and BP of 41 normotensive subjects (aged 25 +/- 4 years) were measured in the first test. A repeatability test was then conducted on 14 subjects after 6 months. Each test included two periods of running on the treadmill at 10 and 8 km/h (with a rest in between). In both tests, systolic BP (SBP) was closely correlated with PTT-foot and PTT-peak. For each subject, the best fit linear relationships between SBP and PTTs were determined over all phases of each test. The differences between the linear fits and measured data were greater after the second period of running for all subjects in both tests. This implied that the relationships started to change after the second period of running. When SBP in the repeatability test was predicted using the linear regression coefficients from the first test, the linear fit after the first period of exercise was still better than after the second. The repeated observations in both tests suggest that PTT is a potential parameter for cuffless BP estimation after one period of exercise, but would need re-calibration (relationship between BP and PTTs) for measurements after successive phases of exercise.