Non-invasive hemoglobin measurement using optical method

Abstract

The measurement of Hemoglobin (Hb) by the non-invasive method is gaining popularity. The system, consisting of a photodiode is placed in between a Red (630 nm) and an IR (940 nm) LED, along with the signal conditioning circuits. 10 healthy male (8) and female (2) volunteers in the age group between 21 and 24 were recruited for this study. During measurement, the fingertip of a volunteer was placed on the measurement pad. Visible and IR lights are switched ON one after the other. The optical absorbance of the blood component in the arteries was detected by the photodiode using the reflectance method. The current generated was converted into voltage and was processed to remove the noise associated with the signal. From this, the concentration of Hb of the volunteers was determined. On the same day they were taken to the clinical laboratory and Hb values were obtained by the standard invasive method. Hemoglobin values obtained from the two methods were compared and an accuracy of 96.31 % and correlation coefficient value of 0.932405 was achieved. From the Bland -Altman plot, the results obtained are within the confidence interval of 95 %. The error of 3 % can be reduced further by employing sophisticated signal conditioning techniques. The proposed non-invasive method took only a few seconds to find the hemoglobin concentration than the invasive lab test. This method can accelerate the decision-making process in emergency situations.

Keywords

• Photoplethysmography
• Beer-Lambert law
• Hemoglobin (Hb)
• Non-invasive