The Heart of the Matter

Many heart issues in patients go undiagnosed. Because of this, unrecognized poor cardiac health reveals itself in the forms of cardiac arrest, heart attacks, and other life-threatening symptoms before it can be treated and these events can be prevented. While an EKG (electrocardiogram) could likely identify these problems, most otherwise healthy people have no reason to undergo the rather involved diagnostic tests required.

In contrast, the non-invasive recording and analysis of a pulse waveform, from anywhere on the body that blood passes through, could reveal abnormalities that prompt patients to seek further tests from physicians before the situation becomes an emergency. Photoplethysmography measures changes in blood volume by the absorption and reflection of red and infrared light in hemoglobin. When light is shined on human flesh, deoxygenated and oxygenated blood absorbs mostly red and infrared wavelengths, respectively. Any light not absorbed by the blood is reflected and captured by a photodiode. This signal is then used to generate a waveform reflecting changes in blood volume and concentration, which can be analyzed to detect concerning heart characteristics.