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Stroke is a global health issue caused by reduced blood flow to the brain, which leads to severe motor disabilities. Measuring oxygen levels in the brain tissue is crucial for understanding the severity and evolution of stroke. While CT or fMRI scans are preferred for confirming a stroke due to their high sensitivity, Near-Infrared Spectroscopy (NIRS)-based systems could be an alternative for monitoring stroke evolution. This study explores the potential of fNIRS signals to assess brain tissue in chronic stroke patients along with rehabilitation therapy. To study the feasibility of this proposal, ten healthy subjects and three stroke patients participated. For signal acquisition, two NIRS sensors were placed on the forehead of the subjects, who were asked to remain in a resting state for 5 min, followed by a 30 s motor task for each hand, which consists of opening and closing the hand at a steady pace, with a 1 min rest period in between. Acomplete protocol for placing sensors and a signal processing algorithm are proposed. In healthy subjects, a measurable change in oxygen saturation was found, with statistically significant differences (females p = 0.016, males p = 0.005) between the resting-state and the hand movement conditions. This work showed the feasibility of the complete proposal, including the NIRS sensor, the placement, the tasks protocol, and signal processing, for monitoring the state of the brain tissue cerebral oxygenation in stroke patients undergoing rehabilitation therapy. Thus this is a non-invasive barin assessment test based on fNIRS with the potential to be implemented in non-controlled clinical environments. [ABSTRACT FROM AUTHOR]

Transcranial direct current stimulation (tDCS) is often reported to have positive effects on brain hemodynamics as well as cognitive performance. Binaural beats (BBs) have also shown the potential to improve cognitive performance. However, we could not find any studies assessing prefrontal hemodynamics using a combination of these techniques or assessing the effects on hemodynamic response at different intensity levels of tDCS (two and three mA). This study aimed to compare the immediate hemodynamic responses to tDCS at different intensities (two and three mA) with and without 40 Hz BBs. Sixty-eight healthy young individuals of both sexes were split into four groups: the tDCS 2 mA group; tDCS 3 mA group; tDCS 2 mA + BB group; and tDCS 3 mA + BB group. All groups received 20 min tDCS (F3-Fp2) alone or combined with BBs. The hemodynamic effect was assessed using a functional near-infrared intracranial spectroscope (fNIRS) positioned on the left supraorbital region (Fp1). The mean values of rates of oxygen saturation (SatO2) were recorded at baseline, during the intervention period, and post-stimulation. The oxygenated hemoglobin rates (HbO) were also extracted. No between-group differences were observed. The within-group analysis did not show significant differences in terms of the time×groups factor. However, the time factor showed significant within-group differences. No differences were found for the HbO rates. The present findings showed that two and three mA tDCS had effects on pre-frontal cortex SatO2; however, the use of additional BBs did not change the SatO2 levels compared to the use of tDCS alone. [ABSTRACT FROM AUTHOR]

Despite the recommendation to treat depression using transcranial direct current stimulation (tDCS), novel findings raise doubts over the tDCS's efficacy in managing depressive episodes. Neurophysiologic approaches to understanding the specificities of brain responses to tDCS in patients with depression remain to be explored. Objective: Our aim was to compare immediate hemodynamic responses to tDCS on the left dorsolateral prefrontal cortex (DLPFC; F3-Fp2 montage) in patients with depressive disorder and in controls (no additional stimuli). Methods: Sixteen participants were allocated to the depression group and sixteen to the control group. Both groups received 2 mA tDCS for 20 min, using the F3-Fp2 montage. The hemodynamic effect over the DLPFC was assessed using functional near-infrared intracranial spectroscopy (fNIRS) positioned on the left supraorbital region (Fp1). Mean, minimal, and maximal values of baseline and post-stimulation rates of oxygen saturation (SatO2) were recorded. The oxygenated hemoglobin rates (HbO) were extracted. Results: Between-group differences were detected for minimal baseline rates of SatO2 and HbO levels. The depression group showed lower results compared to the control group at baseline. After the protocol, only the depression group showed increased minimal rates of SatO2 and HbO. The post-tDCS minimal rates were equal for both groups. Conclusions: The findings showed immediate anodal tDCS effects over DLPFC hemodynamics. The effects were exclusive to the lowest baseline rate group and did not affect the normal oxygen rate group. The minimal increase in SatO2 and HbO rates after the protocol in the depression group suggests that those with reduced cerebral perfusion may be more affected by tDCS. [ABSTRACT FROM AUTHOR]

Determining the level of venous oxygen saturation simultaneously with the saturation of the arterial blood with oxygen allows you to control the oxygen delivery in peripheral tissues of the body. We studied the change in the magnitude of venous blood oxygen saturation during laser-stimulated photodissociation of oxy -hemoglobin. It is shown that only strong changes in the saturation of arterial blood with oxygen lead to a change in the level of venous oxygen saturation. The original optical technique for measurement of venous and arterial blood saturation based on the pulseoximetry is presented [ABSTRACT FROM AUTHOR]

Despite the recommendation to treat depression using transcranial direct current stimulation (tDCS), novel findings raise doubts over the tDCS’s efficacy in managing depressive episodes. Neurophysiologic approaches to understanding the specificities of brain responses to tDCS in patients with depression remain to be explored. Objective: Our aim was to compare immediate hemodynamic responses to tDCS on the left dorsolateral prefrontal cortex (DLPFC; F3-Fp2 montage) in patients with depressive disorder and in controls (no additional stimuli). Methods: Sixteen participants were allocated to the depression group and sixteen to the control group. Both groups received 2 mA tDCS for 20 min, using the F3-Fp2 montage. The hemodynamic effect over the DLPFC was assessed using functional near-infrared intracranial spectroscopy (fNIRS) positioned on the left supraorbital region (Fp1). Mean, minimal, and maximal values of baseline and post-stimulation rates of oxygen saturation (SatO2) were recorded. The oxygenated hemoglobin rates (HbO) were extracted. Results: Between-group differences were detected for minimal baseline rates of SatO2 and HbO levels. The depression group showed lower results compared to the control group at baseline. After the protocol, only the depression group showed increased minimal rates of SatO2 and HbO. The post-tDCS minimal rates were equal for both groups. Conclusions: The findings showed immediate anodal tDCS effects over DLPFC hemodynamics. The effects were exclusive to the lowest baseline rate group and did not affect the normal oxygen rate group. The minimal increase in SatO2 and HbO rates after the protocol in the depression group suggests that those with reduced cerebral perfusion may be more affected by tDCS.

Introduction: Moderate hypoxia may impact cognitive and sensorimotor performance prior to self-recognized impairments. Therefore, rapid and objective assessment tools to identify people at risk of impaired function during moderate hypoxia is needed. Purpose: Test the hypothesis that reductions in arterial oxygen saturation during moderate normobaric hypoxia (FiO2 = 14%) decreases gamified sensorimotor performance as measured by alterations of motor acuity. Methods: Following three consecutive days of practice, thirty healthy adults (25 ± 5 y, 10 females) completed three bouts of the tablet-based gamified assessment (Statespace Labs, Inc.) of motor acuity at Baseline and 60 and 90 min after exposure to 13.8 ± 0.2% (hypoxia) and 20.1 ± 0.4% (normoxia) oxygen. The gamified assessment involved moving the tablet to aim and shoot at targets. Both conditions were completed on the same day and were administered in a single-blind, block randomized manner. Performance metrics included shot time and shot variability. Arterial oxyhemoglobin saturation estimated via forehead pulse oximetry (SpO2). Data were analyzed using linear mixed effects models. Results: Compared to normoxia (99±1%), SpO2 was lower (p<0.001) at 60 (89±3%) and 90 (90±2%) min of hypoxia. Shot time was unaffected by decreases in SpO2 (0.012, p = 0.19). Nor was shot time affected by the interaction between SpO2 decrease and baseline performance (0.006, p = 0.46). Shot variability was greater (i.e., less precision, worse performance) with decreases in SpO2 (0.023, p = 0.02) and depended on the interaction between SpO2 decrease and baseline performance (0.029, p< 0.01). Conclusion: Decreases in SpO2 during moderate hypoxic exposure hinders sensorimotor performance via decreased motor acuity, i.e., greater variability (less precision) with no change in speed with differing decreases in SpO2. Thus, personnel who are exposed to moderate hypoxia and have greater decreases in SpO2 exhibit lower motor acuity, i.e., less precise movements even though decision time and movement speed are unaffected. [ABSTRACT FROM AUTHOR]

Our main objective was to validate that hyperspectral imaging via a new portable camera carries the potential to provide a reliable clinical biomarker that can predict DFU healing. We recruited patients with diabetic foot ulceration (DFU) without peripheral arterial disease, infection or other serious illness. Using an hyperspectral imaging (HSI) apparatus, post‐debridement hyperspectral images were taken evaluating the ulcer size, periwound oxyhemoglobin (OxyHb), deoxyhemoglobin level (DeoxyHb) and oxygen saturation (O2Sat) for four consecutive visits. Twenty‐seven patients were followed, out of whom seven healed their DFU while the remaining 20 failed to heal their DFU. The average time between each visit was 3 weeks. Binary logistic regression of healers versus non‐healers on Visit 1 oxyHb and on Visit 2 showed a significant inverse association, OR = 0.85 (95% CI: 0.73–0.98, p < 0.001). An inverse correlation was observed between the Visit 1 oxyHb and the percentage of ulcer size reduction between Visit 1 and Visit 4 (r = −0.46, p = 0.02) and between the Visit 2 oxyHb and the percentage of ulcer size reduction between Visits 2 and 4 (r = −0.65, p = 0.001). Using oxyHb 50 as the cut‐off point to predict DFU complete healing, Visit 1 oxyHb measurement provided 85% sensitivity, 70% specificity, 50% positive predictive value and 93% negative predictive value. For Visit 2, oxyHb had 85% sensitivity, 85% specificity, 66% positive predictive value and 94% negative predictive value. We conclude that this preliminary study, which involved a relatively small number of patients, indicates that hyperspectral imaging is a simple exam that can easily be added to daily clinical practice and has the potential to provide useful information regarding the healing potential of DFU over a short period of time. [ABSTRACT FROM AUTHOR]

• DRS can measure blood oxygenation parameters from foot sole during leg elevation. • Significant changes in RHb and HbO 2 are seen above 45° of leg elevation. • SO 2 and HR remains same with leg elevation. • PI, ankle SBP and DBP decreases with respect to leg elevation. This study investigated the applicability of diffuse reflectance spectroscopy (DRS) for real-time and non-invasive measurement of blood oxygenation parameters (BOPs) such as reduced hemoglobin (RHb), oxyhemoglobin (HbO 2), and oxygen saturation (SO 2) from human foot sole during leg elevation. Seventeen (17) healthy male subjects aged between 21 to 39 years were included in this study. Diffuse reflectance spectra were recorded from measurement sites namely the 5th metatarsal, ball of great joint, calcaneum, and great toe of the human foot sole w.r.t. leg elevation angles such as 00, 150, 300, 450, and 600, respectively. The localized BOPs were derived from the recorded spectra. In addition, blood hemodynamic parameters (BHPs) such as heart rate (HR), SO 2 , perfusion index (PI), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were also measured for each elevating angle. To study and assess the changes in BOPs and BHPs w.r.t. leg elevation, a One-way ANOVA test followed by a Tukey HSD post-hoc test was performed. We observed a statistically significant increase in RHb (p < 0.001) and a decrease in HbO 2 (p < 0.001) after 45° of leg elevation, however, there was no statistically significant difference in SO 2 (p = 0.74) and HR (p = 0.84) for each measurement site w.r.t. leg elevation, respectively. Furthermore, PI (p < 0.01), ankle SBP (p < 0.001) and DBP (p < 0.001) were decreased w.r.t. leg elevation. The obtained results are in agreement with the literature. The preliminary results suggest that DRS has the potential for real-time estimation of BOPs from the local sites of healthy human foot soles during leg elevation. Thus, it opens the possibility of DRS to monitor and evaluate the diagnosis and treatment of ischemia and edema during leg elevation of patients through BOPs measurement. [ABSTRACT FROM AUTHOR]

Hemoglobin (Hb) possesses good properties of cooperative system and it normally executes oxygen and other essential items via erythrocytes in the body. The chemical action of Hb is to combine with oxygen (O2) in the lungs to form oxyhemoglobin (HbO2). Binding of oxygen with a hemoglobin is one of the important cooperative mechanism and is an emerging mathematical research area with wide range of applications in biomedical engineering and medical physiology. To this end, a mathematical model is proposed to study the fractional saturation of oxygen in hemoglobin to understand the binding effect and its stability at various stages. The mathematical formulation is based on the system of ordinary differential equations together with rate equations under different association and dissociation rate constants. The five states of the cooperative systems Hb, HbO2, Hb(O2)2, Hb(O2)3 and Hb(O2)4 are modelled and the Hill’s function has been used to approximate the binding effect and saturation of ligand (O2) with respect to various rate constants. Also, the Adair equation has been employed to interpret the saturation concentrations of oxygen in hemoglobin. [ABSTRACT FROM AUTHOR]

Introduction. Hyperbaric oxygen therapy is a treatment option for an increasing number of conditions. The aim of this study was to assess its therapeutic effects in femoral condylar necrosis as well as in normal tissue using hyperspectral imaging. Material and method. A 47-year-old female patient diagnosed with avascular necrosis of the medial femoral condyle was included in this study. The patient received hyperbaric oxygen therapy for two consecutive days (the first day: three stages of 30 min each, separated by two breaks of 5 min at pO2 = 2 ATA; the second day: three stages of 30 min each, separated by two breaks of 5 min at pO2 = 2.4 ATA). The effects of hyperbaric oxygen therapy on the affected area (patient’s knee) and normal (patient’s hand) tissues oxygenation were assessed before and after each treatment session using hyperspectral imaging. Results and discussions. The results showed that hyperspectral imaging is quite good for monitoring the hyperbaric oxygen therapy efficacy in affected areas, even with deep tissue problems. Conclusions. In conclusion, the hyperspectral imaging-based approach for monitoring hyperbaric oxygen therapy could support physicians in extracting prognostic information and making the right treatment decisions.

We investigated the relationship between chromophore concentrations in two-layered scattering media and the apparent chromophore concentrations measured with broadband optical spectroscopy in conjunction with commonly used homogeneous medium inverse models. We used diffusion theory to generate optical data from a two-layered distribution of relevant tissue absorbers, namely, oxyhemoglobin, deoxyhemoglobin, water, and lipids, with a top-layer thickness in the range 1–15 mm. The generated data consisted of broadband continuous-wave (CW) diffuse reflectance in the wavelength range 650–1024 nm, and frequency-domain (FD) diffuse reflectance at 690 and 830 nm; two source-detector distances of 25 and 35 mm were used to simulate a dual-slope technique. The data were inverted using diffusion theory for a semi-infinite homogeneous medium to generate reduced scattering coefficients at 690 and 830 nm (from FD data) and effective absorption spectra in the range 650–1024 nm (from CW data). The absorption spectra were then converted into effective total concentration and oxygen saturation of hemoglobin, as well as water and lipid concentrations. For absolute values, it was found that the effective hemoglobin parameters are typically representative of the bottom layer, whereas water and lipid represent some average of the respective concentrations in the two layers. For concentration changes, lipid showed a significant cross-talk with other absorber concentrations, thus indicating that lipid dynamics obtained in these conditions may not be reliable. These systematic simulations of broadband spectroscopy of two-layered media provide guidance on how to interpret effective optical properties measured with similar instrumental setups under the assumption of medium homogeneity. [ABSTRACT FROM AUTHOR]

Objectives: To determine the effects of time after sampling on CO‐oximetry measurements of equine blood samples and the effects of adding ascorbic acid (AscAc) and methylene blue (MetBlue) to samples with methemoglobinemia. Design: Experimental study. Setting: University teaching hospital. Animals: Thirty healthy adult horses assigned to 5 groups. Interventions: Repeated CO‐oximetry determinations were performed on venous (n = 6) and arterial blood samples (n = 7) stored at 0°C for 48 hours. Methemoglobinemia was induced in vitro in 17 additional blood samples. Six were used as untreated controls, 6 had AscAc added, and 5 had MetBlue added. Total hemoglobin, oxyhemoglobin, carboxyhemoglobin, methemoglobin (MetHb), and oxygen saturation of hemoglobin (SO2) were measured. Measurements and Main Results: Oxyhemoglobin and SO2 increased from 69.8% ± 10.2% and 90% ± 3% to 82.8% ± 7.9% and 99% ± 3%, respectively, after 8 hours in venous blood (mean ± SD, P < 0.001). There was an effect of treatment (P = 0.032) and of time (interaction P = 0.003) on MetHb% in methemoglobinemic samples. The difference in absolute MetHb% from time 0 was as follows: 7.0% (interquartile range [IQR] = 21.2), –0.2% (IQR = 3.5), and –4.4% (IQR = 5.2) at 48 hours in control, AscAc, and MetBlue groups, respectively (P < 0.05). There was no effect of time on MetHb% in the AscAc group (23% [IQR = 52.6] at time 0 to 23.2% [IQR = 56.9] after 48 h). Conclusions: Storage of blood in ice water to determine O2Hb and SO2 using a CO‐oximeter should not exceed 4 hours. Measurement of MetHb% could be delayed by up to 48 hours if AscAc is added to the sample. MetBlue significantly decreased MetHb% over time. The limitations of this study include the fact that the antioxidant effects of AscAc and MetBlue were evaluated in vitro and not in vivo. Further studies are needed to evaluate different storage temperatures and syringe types. [ABSTRACT FROM AUTHOR]

Objective: To evaluate if cardiopulmonary coupling (CPC) calculated sleep quality (SQI) may have a role in identifying children that may benefit from other intervention than early adenotonsillectomy (eAT) in management of obstructive sleep apnea (OSA). Methods: A secondary analysis of electrocardiogram-signals (ECG) and oxygen saturation-data (SpO2) collected during polysomnography-studies in the prospective multicenter Childhood Adenotonsillectomy Trial (CHAT) to calculate CPC-SQI and apnea hypopnea index (AHI) was executed. In the CHAT, children 5–9 years with OSA without prolonged oxyhemoglobin desaturations were randomly assigned to adenotonsillectomy (eAT) or watchful waiting with supportive care (WWSC). The primary outcomes were to document change in attention and executive function evaluated with the Developmental Neuropsychological Assessment (NEPSY). In our analysis, children in the WWSC-group with spontaneous resolution of OSA (AHIObstructive < 1.0) and high-sleep quality (SQI ≥ 75) after 7-months were compared with children that showed residual OSA. Results: Of the 227 children randomized to WWSC, 203 children had available data at both baseline and 7-month follow-up. The group that showed resolution of OSA at month 7 (n = 43, 21%) were significantly more likely to have high baseline SQI 79.96 [CI95% 75.05, 84.86] vs. 72.44 [CI95% 69.50, 75.39], p = 0.005, mild OSA AHIObstructive 4.01 [CI95% 2.34, 5.68] vs. 6.52 [CI95% 5.47, 7.57], p= 0.005, higher NEPSY-attention-executive function score 106.22 [CI95% 101.67, 110.77] vs. 101.14 [CI95% 98.58, 103.72], p = 0.038 and better quality of life according to parents 83.74 [CI95% 78.95, 88.54] vs. 77.51 [74.49, 80.53], p = 0.015. The groups did not differ when clinically evaluated by Mallampati score, Friedman palate position or sleep related questionnaires. Conclusions: Children that showed resolution of OSA were more likely to have high-SQI and mild OSA, be healthy-weight and have better attention and executive function and quality of life at baseline. As this simple method to evaluate sleep quality and OSA is based on analyzing signals that are simple to collect, the method is practical for sleep-testing, over multiple nights and on multiple occasions. This method may assist physicians and parents to determine the most appropriate therapy for their child as some children may benefit from WWSC rather than interventions. If the parameters can be used to plan care a priori, this would provide a fundamental shift in how childhood OSA is diagnosed and managed. [ABSTRACT FROM AUTHOR]

Does COVID-19 alter the oxyhemoglobin dissociation curve? Keywords: COVID-19; hemoglobin; hypoxemia; oxygen saturation; oxyhemoglobin dissociation curve EN COVID-19 hemoglobin hypoxemia oxygen saturation oxyhemoglobin dissociation curve e416 e419 4 10/18/21 20210915 NES 210915 To the Editor, Mechanisms leading to hypoxemia in severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) infection are multifactorial and not fully understood [[1]]. Finally, our findings were consistent with another work showing that hemoglobin-oxygen dissociation curves generated from 11 critically ill COVID-19 patients matched the idealized curve, similarly to eleven non-COVID-19 patients [[11]]. [Extracted from the article]

The Elevation Training Mask 2.0 (ETM) is a commercial training mask that purportedly simulates altitude training, although their effects have not been conclusively demonstrated. Therefore, the purpose of this study was to evaluate the influence of wearing the ETM on muscle and brain oxygenation responses during a maximal incremental cycling test, as well as the influence of this device on the heart rate (HR) response, perception of effort (rating of perceived exertion [RPE]), arterial oxygen saturation (SaO2), blood lactate (La+), and performance (POpeak). Fourteen active males completed an incremental cycling test to volitional exhaustion in 2 separate and counterbalanced conditions, wearing the mask set at 9,000 feet (i.e., 2743 m) and a control condition (CTR, without ETM). During the trial, muscle and cerebral oxygenation were monitored continuously using near-infrared spectroscopy. Heart rate, RPE, and SaO2 were also recorded from the beginning of the test until the volitional exhaustion. La+ was measured at the end of each test. Wearing the ETM significantly reduced the POpeak by 26.9 6 6.6% (p = 0.002) and this was accompanied by lower La+ values (212.8 6 21.6%; p = 0.027). SaO2 was also significantly lower at maximal intensity in comparison with the CTR condition (21.5 6 0.3%; p = 0.028). However, both HR and RPE showed a similar trend during both sessions, as well as muscle oxygenation. Nevertheless, the mask caused an increase in brain oxygenation compared with the CTR condition (p, 0.05). In conclusion, our findings suggest that wearing the ETM causes a pronounced increase in O2Hb and tHb in the frontoparietal cortex without any change in the muscle oxygenation. [ABSTRACT FROM AUTHOR]

Introduction. Hyperbaric oxygen therapy is a treatment option for an increasing number of conditions. The aim of this study was to assess its therapeutic effects in femoral condylar necrosis as well as in normal tissue using hyperspectral imaging. Material and method. A 47-year-old female patient diagnosed with avascular necrosis of the medial femoral condyle was included in this study. The patient received hyperbaric oxygen therapy for two consecutive days (the first day: three stages of 30 min each, separated by two breaks of 5 min at pO2 = 2 ATA; the second day: three stages of 30 min each, separated by two breaks of 5 min at pO2 = 2.4 ATA). The effects of hyperbaric oxygen therapy on the affected area (patient's knee) and normal (patient's hand) tissues oxygenation were assessed before and after each treatment session using hyperspectral imaging. Results and discussions. The results showed that hyperspectral imaging is quite good for monitoring the hyperbaric oxygen therapy efficacy in affected areas, even with deep tissue problems. Conclusions. In conclusion, the hyperspectral imaging-based approach for monitoring hyperbaric oxygen therapy could support physicians in extracting prognostic information and making the right treatment decisions. [ABSTRACT FROM AUTHOR]

Determining the level of venous oxygen saturation simultaneously with the saturation of the arterial blood with oxygen allows you to control the oxygen delivery in peripheral tissues of the body. We studied the change in the magnitude of venous blood oxygen saturation during laser-stimulated photodissociation of oxyhemoglobin. It is shown that only strong changes in the saturation of arterial blood with oxygen lead to a change in the level of venous oxygen saturation. The original optical technique for measurement of venous and arterial blood saturation based on the pulse oximetry is presented. [ABSTRACT FROM AUTHOR]

The oxyhemoglobin dissociation curve describes the relationship between the partial pressure of oxygen and the percent of hemoglobin saturated with oxygen and varies with chemical and physical factors that differ for every patient. If variability could be determined, patient-specific oxygen therapy could be administered. We have developed a procedure for characterizing variations in the oxygen dissociation curve. The purpose of this study was to validate this procedure in surgical patients. The procedure uses an automated system to alter oxygen therapy during surgery, within safe operational levels, and fit to Hill's equation non-invasive measurements of end-tidal oxygen and peripheral pulse oxygen saturation. The best-fit parameters for the Hill equation, estimated by iterative least squares, provide an apparent dissociation curve, meaningful of the patient-specific pulse oximeter response. Thirty-nine patients participated in this study. Using patient-specific parameter values increases correlation when compared with standard values. The procedure improved the model fit of patient saturation values significantly in 19 patients. This paper has demonstrated a procedure for determining patient-specific pulse oximeter response. This procedure determined best-fit parameters resulting in a significantly improved fit when compared with standard values. These best-fit parameters increased the coefficient of determination R2 in all cases. Graphical Abstract This patient-specific procedure improves fit significantly compared to standard estimates. [ABSTRACT FROM AUTHOR]

Developing effective photodynamic theranostics for real-time monitoring of oxygen saturation at a specific target for photodynamic therapy (PDT) is highly desirable, but remains a great challenge owing to the separation of monitoring units and PDT units in existing methods. In this study, we report the real-time monitoring of tissue oxygen saturation (StO 2 ) during PDT using an 808 nm-excited upconversion nanoagent, UCNP-RB-RGD, fabricated by loading the photosensitiser rose bengal (RB) into amphiphilic upconversion nanoparticles, followed by conjugation with the tumour-targeting peptide c(RGDyK). Using the as-prepared UCNP-RB-RGD, we demonstrated that the upconversion luminescence at 645 nm and 540 nm under 808 nm laser irradiation could be used to simultaneously monitor StO 2 and activate RB for PDT. Furthermore, benefitting from this new photodynamic theranostic approach, the PDT efficacy was significantly enhanced by controllable adjuvant oxygen inhalation to resist the consumption of oxygen. The StO 2 monitoring unit and PDT unit were integrated into the single nanoagent UCNP-RB-RGD, providing high spatiotemporal consistency for the photo-controlled monitoring of StO 2 and localised activation of PDT; this system has potential for effective and accurate personalised PDT. [ABSTRACT FROM AUTHOR]

We hypothesize that noninvasive photoacoustic imaging can accurately measure cerebral venous oxyhemoglobin saturation (SO2) in a neonatal model of hypoxia-ischemia. In neonatal piglets, which have a skull thickness comparable to that of human neonates, we compared the photoacoustic measurement of sagittal sinus SO2 against that measured directly by blood sampling over a wide range of conditions. Systemic hypoxia was produced by decreasing inspired oxygen stepwise (i.e., 100, 21, 19, 17, 15, 14, 13, 12, 11, and 10%) with and without unilateral or bilateral ligation of the common carotid arteries to enhance hypoxiaischemia. Transcranial photoacoustic sensing enabled us to detect changes in sagittal sinus O2 saturation throughout the tested range of 5-80% without physiologically relevant bias. Despite lower cortical perfusion and higher oxygen extraction in groups with carotid occlusion at equivalent inspired oxygen, photoacoustic measurements successfully provided a robust linear correlation that approached the line of identity with direct blood sample measurements. Receiver-operating characteristic analysis for discriminating SO2 < 30% showed an area under the curve of 0.84 for the pooled group data, and 0.87, 0.91, and 0.92 for hypoxia alone, hypoxia plus unilateral occlusion, and hypoxia plus bilateral occlusion subgroups, respectively. The detection precision in this critical range was confirmed with sensitivity (87.0%), specificity (86.5%), accuracy (86.8%), positive predictive value (90.5%), and negative predictive value (81.8%) in the combined dataset. These results validate the capability of photoacoustic sensing technology to accurately monitor sagittal sinus SO2 noninvasively over a wide range and support its use for early detection of neonatal hypoxia-ischemia. NEW & NOTEWORTHY We present data to validate the noninvasive photoacoustic measurement of sagittal sinus oxyhemoglobin saturation. In particular, this paper demonstrates the robustness of this methodology during a wide range of hemodynamic and physiological changes induced by the stepwise decrease of fractional inspired oxygen to produce hypoxia and by unilateral and bilateral ligation of the common carotid arteries preceding hypoxia to produce hypoxiaischemia. This technique may be useful for diagnosing risk of neonatal hypoxic-ischemic encephalopathy. [ABSTRACT FROM AUTHOR]

Purpose: To define if the pressure support of Continuous Positive Airway Pressure (CPAP) therapy can determine the severity of apnea concerning Apnea Hypopnea Index (AHI) and desaturation of oxyhemoglobin. Methods: A cross-sectional study that selected 27 patients followed in the Sleep outpatient of a Statewide Hospital in the city of Santo André, Brazil, which carried out exams as polysomnography type 3 and test with CPAP. Data was tabulated, holding patient's information (age, gender and BMI), values found in polysomnography (AHI, oxygen desaturation index - ODI, and sleep time with oxygen saturation below 90% - ST90) and in test with CPAP (AIH and pressure support), as well as the outcome (prescription of CPAP or not). Based on the data collected, exploratory and statistical analysis were made. Results: Descriptive analysis of the sample evidenced majority of patients classified as severe Obstructive Sleep Apnea (AHI>30). The correlation analysis showed statistical significance only with the support pressure of CPAP and ST90. For the support pressure was observed statistical difference of ST90 between both groups, with higher values for the group with support pressure >10cmH2O. The descriptive analysis of the outcome found that patients which required support pressure >10cmH2O presented higher ST90, leading to the prescription of CPAP for 75% of them. The comparative analysis of the outcome could not find relation between AHI and prescription of CPAP. Conclusion: Patients with the necessity of pressure support of CPAP >10cmH2O has increased odd of running with desaturation of oxyhemoglobin (ST90) when subjected to sleep monitoring. [ABSTRACT FROM AUTHOR]

Laboratory-based studies on the oxyhemoglobin dissociation curve (ODC) suggest that high blood temperature decreases the affinity of hemoglobin for oxygen. The aim of the study was to evaluate the influence of pyrexia on oxygen saturation (SpO2) in children presenting to the emergency department. Normoxemic children with body temperature at or above 38.5 °C were included. Patients with a dynamic respiratory disease were excluded. SpO2 was measured before and after antipyretic treatment. The changes in body temperature and SpO2 were assessed and compared to the changes predicted from the ODC. Thirty-four children completed the study. Mean temperature at presentation was 39.17 ± 0.549 °C and mean SpO2 was 96.15 ± 2.21%. The mean decrease in temperature after antipyretic treatment was 1.71 ± 0.67 °C and mean increase in SpO2 was 0.95 ± 1.76%. Among children in whom pyrexia decreased by 1.5 °C or more, the mean increase in SpO2 was 1.45 ± 1.57%. The measured increase in SpO2 was close to the increase anticipated from the ODC.Conclusion: Pyrexia was associated with decreased SpO2 in normoxemic children. The influence of pyrexia in children with low-normal oxygen saturation is expected to be much higher because of the non-linear shape of the ODC. Physicians treating patients with fever should be aware of this effect, especially in patients with borderline hypoxia. What is Known: • High blood temperature decreases the affinity of oxygen to hemoglobin. • It is not known whether fever would decrease SpO 2 . What is New: • Fever is associated with decreased SpO 2 . [ABSTRACT FROM AUTHOR]

Testing the human body's reaction to hypoxia (including the one generated by high altitude) is important in aeronautic medicine. This paper presents a method of monitoring blood oxygenation during experimental hypoxia using hyperspectral imaging (HSI) and a spectral unmixing model based on a modified Beer--Lambert law. A total of 20 healthy volunteers (males) aged 25 to 60 years were included in this study. A line-scan HSI system was used to acquire images of the faces of the subjects. The method generated oxyhemoglobin and deoxyhemoglobin distribution maps from the foreheads of the subjects at 5 and 10 min of hypoxia and after recovery in a high oxygen breathing mixture. The method also generated oxygen saturation maps that were validated using pulse oximetry. An interesting pattern of desaturation on the forehead was discovered during the study, showing one of the advantages of using HSI for skin oxygenation monitoring in hypoxic conditions. This could bring new insight into the physiological response to high altitude and may become a step forward in air crew testing. [ABSTRACT FROM AUTHOR]

We develop a theory of oxygen hemoglobin association and derive the oxygen hemoglobin association equation and determine the values of the four association constants by curve fitting four commonly accepted data points that relate oxygen saturation and oxygen partial pressure (PO 2) in the blood using mathematical reasoning and chemical kinetics. The four association constants come from the progression of oxygen binding to each of the four subunits on the hemoglobin molecule in a cooperative manner. The binding of oxygen alters the affinity of subsequent binding of additional oxygen molecules, which is reflected in changing magnitudes of the association constants. We also demonstrate rather surprisingly that the value of the third association constant is significantly smaller than all other association constants and offer some conjecture about this puzzling finding. With our equation, we can compute the distributions of all five oxyhemoglobin species at various PO 2 levels that are published for the first time in the history of hemoglobin research. After examining the distributions, we find the triply bound oxyhemoglobin exists in very low concentration, consistent with the small third association constant. In addition, we present the oxygen levels where maximal concentrations of various oxyhemoglobin species occur, another unexpected finding that was never published before. Finally, we determine the inflection point of the hemoglobin association curve, a defining property to a specific sigmoid curve, representing the steepest portion of the curve. One sentence summary : We develop a theory of oxygen hemoglobin association based upon first order chemical kinetics and the principle of cooperativity and provide for the first time accurate oxygen hemoglobin association constants for each step of the four steps of oxygen and hemoglobin binding. [ABSTRACT FROM AUTHOR]

The oxygen binding capacity of human erythrocytes in selected solutions was studied in vitro. Three treatment groups were used in the study: 0.08% ι‐carrageenan solution, dextran 70, and normal saline solution (NSS). The different treatment groups were oxygenated. The percent oxygen saturation and oxygen partial pressure were determined by blood gas analysis, and oxyhemoglobin absorbance was measured using spectrophotometry. Analysis of variance (ANOVA) and Tukey's HSD Test were used to analyze the data. There were significant differences (p<0.05) observed in the percent oxygen saturations and oxygen partial pressures among the three treatment groups, with NSS having the highest values (97.65±0.385% and 160.18±152.567 mmHg, respectively) followed by dextran 70 (95.38±1.093% and 142.68±73.967 mmHg, respectively) then ι‐carrageenan (89.42±4.327% and 94.02±17.912 mmHg, respectively). However, there were no significant differences observed in the absorbance values of oxyhemoglobin among the three set‐ups. It was concluded that the oxygen binding capacity of erythrocytes in ι‐carrageenan solution is significantly lower than that in dextran 70 and NSS. [ABSTRACT FROM AUTHOR]

Significance: Many studies in colorectal cancer (CRC) use murine ectopic tumor models to determine response to treatment. However, these models do not replicate the tumor microenvironment of CRC. Physiological information of treatment response derived via diffuse reflectance spectroscopy (DRS) from murine primary CRC tumors provide a better understanding for the development of new drugs and dosing strategies in CRC. Aim: Tumor response to chemotherapy in a primary CRC model was quantified via DRS to extract total hemoglobin content (tHb), oxygen saturation (StO2), oxyhemoglobin, and deoxyhemoglobin in tissue. Approach: A multimodal DRS and imaging probe (0.78 mm outside diameter) was designed and validated to acquire diffuse spectra longitudinally—via endoscopic guidance—in developing colon tumors under 5-fluoruracil (5-FU) maximum-tolerated (MTD) and metronomic regimens. A filtering algorithm was developed to compensate for positional uncertainty in DRS measurements Results: A maximum increase in StO2 was observed in both MTD and metronomic chemotherapy-treated murine primary CRC tumors at week 4 of neoadjuvant chemotherapy, with 21 ± 6 % and 17 ± 6 % fold changes, respectively. No significant changes were observed in tHb. Conclusion: Our study demonstrates the feasibility of DRS to quantify response to treatment in primary CRC models. [ABSTRACT FROM AUTHOR]