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Effect of source wavelength on second derivative of finger photoplethysmogram in healthy young female volunteers

Revati Shriram, Betty Martin, Sundhararajan M, Nivedita Daimiwal

Background: Non-invasive methods for screening and diagnosis are the field with fast growing interest which leads to various biological signal measurements like Photoplethysmogram (PPG) and pressure pulse. PPG monitoring is widely used in the healthcare as this single pulse study can provide wide physiological information non-invasively such as oxygen saturation, heart rate, blood pressure (continuous and cuff less), blood volume, arterial stiffness and respiration rate. First and second derivatives of PPG provide important information about the arterial stiffness and vascular health of the person.

Aim: This paper explains the design and development of prototype with RED LED (660 nm) and IR LED (860 nm) as a source and OPT 101 as a detector. Second derivative related indices of PPG (for RED LED and IR LED) were calculated.

Materials and methods: Study was carried out on 15 healthy female subjects without any known history of blood pressure and blood glucose; aged between 19-23 years.

Results and conclusion: Amplitude of PPG obtained from RED LED is smaller than the amplitude of PPG obtained from IR LED. Comparative analysis of first and second derivative of the PPG obtained from RED light source and IR light source is discussed by the authors. It was observed that various parameters studied from second derivative are the ‘Normalized Values’, so effect of change in the amplitude of the PPG signal obtained from RED LED and IR LED get nullified in this study (P>0.05). Though IR source based reflective type of sensor related study can be useful in future for the brain vascular health assessment.