Camera-based pulse-oximetry - validated risks and opportunities from theoretical analysis

Abstract

Camera-based pulse-oximetry has recently shown to be feasible, even when the signal is corrupted by noise and motion artifacts. Earlier work showed that using three instead of the common two wavelengths improves robustness of the measurement, however without a thorough investigation on the optimal wavelength selection. We therefore performed a search to identify these wavelengths to further improve the robustness of the measurement. Besides motion, it is empirically known that there are several other factors that influence the measurement leading to falsely-low or falsely-high SpO readings. These factors include the presence of dyshemoglobins or other species. In this paper, we use a theoretical skin-model to study how these factors influence the measurement, and how a proper wavelength selection can reduce the impact on the measurement. Additionally, we show that adding a third wavelength does not only improve robustness, but can also be exploited to create a reliability index for the measurement. Finally, we show that the presence of dyshemoglobins in arterial blood can not only be detected but also quantified. We illustrate this by comparing the estimated COHb levels of a small group of smokers and non-smokers, which typically have different CO-levels.

Noninvasive hemoglobin sensing and imaging: optical tools for disease diagnosis

“…11 , 13 , 14 Hemoglobin is also able to bind to other molecules forming carboxyhemoglobin, which arises during carbon monoxide inhalation; 15 , 16 sulfhemoglobin, which arises due to the irreversible binding of sulphur in the presence of sulfonamides; 17 and carbaminohemoglobin, which results from the binding of hemoglobin in venous blood to carbon dioxide. 18 A further variant state of hemoglobin is methemoglobin, 19 – 21 in which hemoglobin binds iron in the state (unlike normal hemoglobin that binds ), which prevents the binding of oxygen. Methemoglobin occurs naturally in blood at to 2% concentration, 15 but it can be elevated due to side effects of medication or environmental factors.…”

Noncontact Physiological Measurement Using a Camera: A Technical Review and Future Directions

“…Gastel et al 81 proposed a method to measure SpO 2 even during significant subject motion based on a blood volume pulse signature. In another work, 82 the authors discussed how wavelength selection is important for a camerabased pulse-oximetry and suggested adding a third wavelength to improve measurement robustness. Using similar camera-based settings, they further showed monitoring carboxyhemoglobin (COHb) level was also feasible.…”

TeleVital: Enhancing the quality of contactless health assessment

“…And this leads to overcrowding of hospitals and clinics and brings about an imbalance in the healthcare system. Therefore, it is necessary to handle this situation by analyzing the health of the patient at their homes itself (Gastel et al, 2018;Iozzia et al, 2017;J. Ben-Ari, 2010;Malasinghe et al, 2017;Massaroni et al, 2018).…”