Evaluation of hypertension using first derivative features of photoplethysmography / 国际药学研究杂志

ABSTRACT

The photoplethysmography (PPG) signal is the standard technique to measure blood oxygen saturation and cardiac output, but the complete diagnostic value of PPG signals is not being used presently in clinical applications. Therefore, we are proposing a simple algorithm to extract blood flow parameters from the PPG signals and prove that blood vessels are altered, losing their elasticity in hypertensive people. Hypertension is a serious medical condition where the force of blood pumping through the arteries is strong as compared to the normal force. Hypertension is defined as blood pressure above 140/90mmHg and is considered to be severe if it exceeds 180/120mmHg. Blood pressure can be measured using various methods like auscultatory method and palpatory method. The manual method of blood pressure measurements based on a calibrated sphygmomanometer will be accurate only if performed precisely. A PPG sensor shows us the vascular condition of a person by allowing us to calculate blood flow parameters like systolic amplitude, pulse interval, augmentation index and stiffness index. Our study population includes 25 normal and 25 known hypertensive subjects. Parameters from PPG signal like systolic amplitude, pulse interval, and stiffness index was calculated directly. After taking first derivative of the signal features like i). Crest Time (CT), ii). Peak to peak time (ΔT) and iii). Stiffness index was also calculated. The parameters were statistically analyzed to prove that there is vascular wall health deterioration in prolonged hypertensive subjects.