Noncontact Monitoring of Blood Oxygen Saturation Using Camera and Dual-Wavelength Imaging System

Abstract

We present a noncontact method to monitor blood oxygen saturation (SpO2). The method uses a CMOS camera with a trigger control to allow recording of photoplethysmography (PPG) signals alternatively at two particular wavelengths, and determines the SpO2 from the measured ratios of the pulsatile to the nonpulsatile components of the PPG signals at these wavelengths. The signal-to-noise ratio (SNR) of the SpO2 value depends on the choice of the wavelengths. We found that the combination of orange (λ = 611 nm) and near infrared (λ = 880 nm) provides the best SNR for the noncontact video-based detection method. This combination is different from that used in traditional contact-based SpO 2 measurement since the PPG signal strengths and camera quantum efficiencies at these wavelengths are more amenable to SpO2 measurement using a noncontact method. We also conducted a small pilot study to validate the noncontact method over an SpO2 range of 83%-98%. This study results are consistent with those measured using a reference contact SpO2 device ( r = 0.936, ). The presented method is particularly suitable for tracking one's health and wellness at home under free-living conditions, and for those who cannot use traditional contact-based PPG devices.

New principle for measuring arterial blood oxygenation, enabling motion-robust remote monitoring

“…heart rate variability (HRV). However, camera-based SpO 2 measurement has also been attempted in the last few years567891011121314151617. Besides the advantage that a camera does not require direct skin contact, it has the potential to be more robust by exploiting the spatial redundancy of the camera sensor, which is not possible with the single-spot measurement of a contact sensor.…”

“…by using the red and blue color channels of a single RGB camera. Another single camera approach has been presented by Shao et al 16,. but instead of using ambient light illumination, a trigger-controlled dual wavelength LED-array was proposed to measure the PPG signal at different wavelengths with a monochromatic camera.…”

Remote patient monitoring: a comprehensive study

“…Use of dual-wavelength imaging system to find blood oxygen saturation is shown in Shao et al (2016). Planar and avalanche photodiodes against IR and visible light wavelengths for the purpose of usage as non-invasive cardiovascular monitoring are compared in paper .…”

Estimation of oxygen saturation with laser optical imaging method

“…It is important to determine whether a person has adequately supply oxygen. Also the continuous montioring of oxygen saturation is important for detecting hypoxemia condition [12]. For human body, estimation of arterial oxygen saturation at peripheral capillary is called SpO2 which is primary focus of clinical conditions.…”

“…where HbO2 is the concentration of oxygenated hemoglobin and Hb is the concentration of deoxygenated hemoglobin [12]. Generally, in clincial conditions SpO2 is measured depending on the selected two wavelengths; λ1 and λ2 such that absorbance by HbO2 is more at at λ2 than at λ1 while the absorbance by Hb is more at λ1 than at λ2, as given in Figure 1.…”