PMC

Vascular occlusion monitoring with the smartphone-based hyperspectral imaging system. (a) Representative RGB frame at 60s from the monitoring video during vascular occlusion on the middle finger. (b) Blood absorption map at 60s extracted from hyperspectral reconstruction based on the RGB frame in (a) (color-coded according to color bar shown in the right). (c) Oxygen saturation map at 60s extracted from hyperspectral reconstruction based on the RGB frame in (a) (color-coded according to color bar shown in the right). (d) Real-time response curves of blood absorption intensities on middle finger during vascular occlusion. The intensities were normalized summations of blood absorption intensities in corresponding color box areas in (a): Experiment group: black curve: box 1, mid-finger. Control group: red curve: box 2, forefinger; green curve: box 3, index finger; blue curve: box 4, little finger; teal curve: box 5, thumb. (e) Real-time response curves of oxygen saturation intensities on finger skins during vascular occlusion. The intensities were normalized summations of oxygen saturation intensities in corresponding color box areas in (a). Experiment group: black curve: box 1, mid-finger. Control group: red curve: box 2, forefinger; green curve: box 3, index finger; blue curve: box 4, little finger; teal curve: box 5, thumb). (f) Visualization of RGB frames, blood absorption maps and oxygen saturation maps at 10s, 50s, 70s and 110s from the monitoring video to vascular occlusion on middle finger. Blood absorption maps were color-coded according to color bar shown in (b). Oxygen saturation maps were color-coded according to color bar shown in (c).

The relationship between end-tidal carbon dioxide and cerebral saturation demonstrating the linear relationship between the two variables (individual points in blue diamonds). The curve fit the equation y = 2.16×−112. The linear curve fit for these data was R² = 0.98. The relationship between end-tidal oxygen and cerebral saturation demonstrating the log-linear relationship between the two variables (individual points in red squares). The hyperbolic curve fit for these data was R² = 0.96. The curve fit the equation y = b/(x−a): where b = −774 and a = 72.8; the asymptote for maximal saturation for hyperoxia.

Using a threshold S_cvO₂ of 53% (mean S_pO₂-25 as a surrogate for a clinically acceptable arteriovenous oxygen difference less than 25), the area under the receiver operating characteristic curve is .78, demonstrating good discrimination between clinically low and acceptable levels of S_cvO₂ using S_tO₂. S_cvO₂ = central venous oxygen saturation; S_pO₂, oxygen saturation; S_tO₂, tissue oxygen saturation.