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Significance: Untreated methemoglobinemia may cause severe hypoxemia and even death when methemoglobin levels in the blood stream exceed 70%. Although CO-oximetry can be used to monitor the response to treatment for methemoglobinemia, it is costly and requires an invasive procedure for collecting blood samples from patients. A pulse CO-oximeter with a contact probe can be used to continuously and non-invasively measure the percentage of methemoglobin, as well as the percutaneous oxygen saturation. In terms of the prevention of infectious diseases, however, it is desirable to monitor methemoglobin and oxygen saturation levels in a non-contact manner. Diffuse reflectance spectral imaging is promising as a non-contact, non-invasive, and cost-effective clinical diagnostic tool for methemoglobinemia. Aim: To demonstrate the feasibility of visible spectral diffuse reflectance for in vivo monitoring of hemoglobin derivatives and evaluating methemoglobin production and reduction as well as hypoxemia during methemoglobinemia in rats. Approach: A new imaging approach based on the multiple regression analysis aided by Monte Carlo simulations for light transport was developed to quantify methemoglobin, oxygenated hemoglobin, and deoxygenated hemoglobin using a hyperspectral imaging system. An in vivo experiment with rats exposed to sodium nitrite (NaNO2) at different doses was performed to confirm the feasibility of the method for evaluating the dynamics of methemoglobin, oxygenated hemoglobin, and deoxygenated hemoglobin during methemoglobinemia. Systemic physiological parameters, including the percutaneous arterial oxygen saturation, heart rate (HR), and pulse distention, were measured by a commercially available pulse oximeter, and the results were compared to those obtained by the proposed method. Results: Both the methemoglobin concentration and methemoglobin saturation rapidly increased with a half-maximum time of <20 min. They reached their maximal values nearly 60 min a

Peripheral hemodynamics, measured via the blood volume pulse and vasomotion, provide a valuable way of monitoring physiological state. Camera imaging-based systems can be used to measure these peripheral signals without contact with the body, at distances of multiple meters. While researchers have paid attention to non-contact imaging photoplethysmography, the study of peripheral hemodynamics and the effect of autonomic nervous system activity on these signals has received less attention. Using a method, based on a tissue-like model of the skin, we extract melanin Cm and hemoglobin CHbO concentrations from videos of the hand and face and show that significant decreases in peripheral pulse signal power (by 36% +/- 29%) and vasomotion signal power (by 50% +/- 26%) occur during periods of cognitive and psychological stress. Via three experiments we show that similar results are achieved across different stimuli and regions of skin (face and hand). While changes in peripheral pulse and vasomotion power were significant the changes in pulse rate variability were less consistent across subjects and tasks.

Cyanosis is a pathological condition that is characterized by a bluish discoloration of the skin or mucous membranes. It may result from a number of medical conditions, including disorders of the respiratory system and central nervous system, cardiovascular diseases, peripheral vascular diseases, deep vein thrombosis, and regional ischemia. Cyanosis can also be elicited from methemoglobin. Therefore, a simple, rapid, and simultaneous monitoring of changes in oxygenated hemoglobin and deoxygenated hemoglobin is useful for protective strategies against organ ischemic injury. We previously developed a red-green-blue camera-based spectral imaging method for the measurements of melanin concentration, oxygenated hemoglobin concentration (C-HbO), deoxygenated hemoglobin concentration (C-Hb(R)), total hemoglobin concentration (C-HbT) and tissue oxygen saturation (StO(2)) in skin tissues. We leveraged this approach in this study and extended it to the simultaneous quantifications of methemoglobin concentration (C-metHb), C-HbO, C-Hb(R), and StO(2). The aim of the study was to confirm the feasibility of the method to monitor C-metHb, C-HbO, C-Hb(R), C-HbT, and StO(2). We performed in vivo experiments using rat dorsal skin during methemoglobinemia induced by the administration of sodium nitrite (NaNO2) and changing the fraction of inspired oxygen (FiO(2)), including normoxia, hypoxia, and anoxia. Spectral diffuse reflectance images were estimated from an RGB image by the Wiener estimation method. Multiple regression analysis based on Monte Carlo simulations of light transport was used to estimate C-HbO, C-HbR, C-metHb, C-HbT, and StO(2). C-metHb rapidly increased with a half-maximum time of less than 30 min and reached maximal values nearly 60 min after the administration of NaNO2, whereas StO(2) dramatically dropped after the administration of NaNO2, indicating the temporary production of methemoglobin and severe hypoxemia during methemoglobinemia. Time courses of C-HbT and S

Significance: Untreated methemoglobinemia may cause severe hypoxemia and even death when methemoglobin levels in the blood stream exceed 70%. Although CO-oximetry can be used to monitor the response to treatment for methemoglobinemia, it is costly and requires an invasive procedure for collecting blood samples from patients. A pulse CO-oximeter with a contact probe can be used to continuously and non-invasively measure the percentage of methemoglobin, as well as the percutaneous oxygen saturation. In terms of the prevention of infectious diseases, however, it is desirable to monitor methemoglobin and oxygen saturation levels in a non-contact manner. Diffuse reflectance spectral imaging is promising as a non-contact, non-invasive, and cost-effective clinical diagnostic tool for methemoglobinemia. Aim: To demonstrate the feasibility of visible spectral diffuse reflectance for in vivo monitoring of hemoglobin derivatives and evaluating methemoglobin production and reduction as well as hypoxemia during methemoglobinemia in rats. Approach: A new imaging approach based on the multiple regression analysis aided by Monte Carlo simulations for light transport was developed to quantify methemoglobin, oxygenated hemoglobin, and deoxygenated hemoglobin using a hyperspectral imaging system. An in vivo experiment with rats exposed to sodium nitrite (NaNO2) at different doses was performed to confirm the feasibility of the method for evaluating the dynamics of methemoglobin, oxygenated hemoglobin, and deoxygenated hemoglobin during methemoglobinemia. Systemic physiological parameters, including the percutaneous arterial oxygen saturation, heart rate (HR), and pulse distention, were measured by a commercially available pulse oximeter, and the results were compared to those obtained by the proposed method. Results: Both the methemoglobin concentration and methemoglobin saturation rapidly increased with a half-maximum time of <20 min. They reached their maximal values nearly 60 min a

Cyanosis is a pathological condition that is characterized by a bluish discoloration of the skin or mucous membranes. It may result from a number of medical conditions, including disorders of the respiratory system and central nervous system, cardiovascular diseases, peripheral vascular diseases, deep vein thrombosis, and regional ischemia. Cyanosis can also be elicited from methemoglobin. Therefore, a simple, rapid, and simultaneous monitoring of changes in oxygenated hemoglobin and deoxygenated hemoglobin is useful for protective strategies against organ ischemic injury. We previously developed a red-green-blue camera-based spectral imaging method for the measurements of melanin concentration, oxygenated hemoglobin concentration (C-HbO), deoxygenated hemoglobin concentration (C-Hb(R)), total hemoglobin concentration (C-HbT) and tissue oxygen saturation (StO(2)) in skin tissues. We leveraged this approach in this study and extended it to the simultaneous quantifications of methemoglobin concentration (C-metHb), C-HbO, C-Hb(R), and StO(2). The aim of the study was to confirm the feasibility of the method to monitor C-metHb, C-HbO, C-Hb(R), C-HbT, and StO(2). We performed in vivo experiments using rat dorsal skin during methemoglobinemia induced by the administration of sodium nitrite (NaNO2) and changing the fraction of inspired oxygen (FiO(2)), including normoxia, hypoxia, and anoxia. Spectral diffuse reflectance images were estimated from an RGB image by the Wiener estimation method. Multiple regression analysis based on Monte Carlo simulations of light transport was used to estimate C-HbO, C-HbR, C-metHb, C-HbT, and StO(2). C-metHb rapidly increased with a half-maximum time of less than 30 min and reached maximal values nearly 60 min after the administration of NaNO2, whereas StO(2) dramatically dropped after the administration of NaNO2, indicating the temporary production of methemoglobin and severe hypoxemia during methemoglobinemia. Time courses of C-HbT and S

Peripheral hemodynamics, measured via the blood volume pulse and vasomotion, provide a valuable way of monitoring physiological state. Camera imaging-based systems can be used to measure these peripheral signals without contact with the body, at distances of multiple meters. While researchers have paid attention to non-contact imaging photoplethysmography, the study of peripheral hemodynamics and the effect of autonomic nervous system activity on these signals has received less attention. Using a method, based on a tissue-like model of the skin, we extract melanin Cm and hemoglobin CHbO concentrations from videos of the hand and face and show that significant decreases in peripheral pulse signal power (by 36% +/- 29%) and vasomotion signal power (by 50% +/- 26%) occur during periods of cognitive and psychological stress. Via three experiments we show that similar results are achieved across different stimuli and regions of skin (face and hand). While changes in peripheral pulse and vasomotion power were significant the changes in pulse rate variability were less consistent across subjects and tasks.