Assessment of Photoplethysmography Method in Extraction of Hemoglobin Concentration

The importance of continuous monitoring along with rapid and accurate notification of changes in blood components such as hemoglobin concentration, especially in acute situations, encourages researchers to use non-invasive methods for measuring.

This study was aimed to investigate the correlation between hemoglobin concentration and photoplethysmogram (PPG) and the possibility of measuring it by an optical method.

In this applied study, a PPG signal was simultaneously recorded at four different wavelengths for thirty subjects who were referred to the laboratory for a hemoglobin concentration test. After calibrating the special recording probe with a standard pulse oximeter system and applying the required preprocessing on the obtained signals, the peak-to-peak value of PPG signals was extracted. Finally, the correlation between the peak-to-peak value of the signal at a certain wavelength and hemoglobin concentration was analyzed using Spearman and Pearson correlation for determining the process of changes in the data.

The results demonstrated that based on the normal distribution of data at 590 nm wavelength, there is a significantly negative correlation between a function of the signal peak slope and the hemoglobin concentration, with a Pearson coefficient of -0.787 (p<0.01). In addition, the investigation of rank correlation indicated a significantly negative correlation of -0.842 (p<0.01) using Spearman correlation analysis.

Considering the high correlation between hemoglobin concentration and PPG signal characteristics, optical methods can be used to develop a rapid, precise, clean and inexpensive method to measure hemoglobin concentration.