Study on the variability of pulse wave and ECG of graduate students with different body positions

Aims: To study the variations of pulse and ECG with different body positions. Methods: A device with a pressure-adjustable pulse sensor and an ECG sensor is used to acquire radial pulse wave and ECG signals, and a cuff sphygmomanometer is used to measure the blood pressure (BP). The signals are recorded continuously at different positions (supine, a series of transitional positions from supine to standing and standing position) for 20 subjects with age 24 ± 3(11 males, 9 females). Results: It is observed that the pulse contours of 20 subjects have two kinds of waveforms: one group has a tidal wave, while the other does not. In Group 1, the time that the valley of tidal wave occurred has no significant difference from supine to standing. The change of left ventricular ejection time (LVET) in Group 2 is larger than that in Group 1. During the procedure from supine to standing, the diastole period of the 95% subjects in two groups gets shorter, and all subjects' heart rate (HR) gradually accelerated. Meanwhile, pulse wave transit time (PWTT) decreases from supine to standing. In supine position, 100% subjects' diastole blood pressure (DBP) significantly decreased about 11.2 mmHg and 90% subjects' systolic blood pressure (SBP) reduced about 7.7 mmHg, which is consistent with the references. Conclusions: The experimental results demonstrate the diastole gets longer in supine position. The longer diastole helps the heart to get more rest time. Furthermore, blood pressure (BP) significantly decreased in supine which benefits cardiovascular system. Therefore, the supine position is a relatively ideal position in daily examining and clinical monitoring.