HEART RATE VARIABILITY DERIVED FROM WRIST PHOTOPLETHYSMOGRAPHY SENSOR FOR MENTAL STRESS ASSESSMENT

Noor Aimie-Salleh, Nurul Aliaa Abdul Ghani, Norhafizah Hasannudin, Aisyah Ahmad Shafi

Abstract

Generally, mental illness is an abstract condition that is difficult to be measured. However, there is a strong relation of human mental state with several physiological processes in the human body such as changes in heart rate variability (HRV). HRV has the potential to provide additional valuable insight into physiological and pathological condition of human heart. In clinical basis, ECG has been used for years to measure HRV for stress assessment. However, this technique causes slight discomfort to the patients and is inconvenient for application in long-term stress monitoring device. The introduction of pulse rate monitor allows easy monitoring of these parameters but its accuracy and reliability are still uncertain. This study aimed to study the relation of HRV feature with mental stress by using photoplethysmograph (PPG). The PPG signals were collected from 12 healthy adults during resting and arithmetic stress test by using both PPG and ECG. HRV features were then extracted using time-domain analysis (TA), frequency-domain analysis (FA) and non-linear time-frequency analysis (TFA). From the results, it can be seen that most HRV features extracted using PPG showed significant correlation (p < 0.01) between HRV features extracted from ECG. This concludes that, PPG can be used as an alternative tool to measure the HRV during mental stress test as it is much more convenient for stress assessment yet performs as an accurate measure.