Innovative Predictive Approach towards a Personalized Oxygen Dosing System

Despite the large impact chronic obstructive pulmonary disease (COPD) that has on the population, the implementation of new technologies for diagnosis and treatment remains limited. Current practices in ambulatory oxygen therapy used in COPD rely on fixed doses overlooking the diverse activities which patients engage in. To address this challenge, we propose a software architecture aimed at delivering patient-personalized edge-based artificial intelligence (AI)-assisted models that are built upon data collected from patients' previous experiences along with an evaluation function. The main objectives reside in proactively administering precise oxygen dosages in real time to the patient (the edge), leveraging individual patient data, previous experiences, and actual activity levels, thereby representing a substantial advancement over conventional oxygen dosing. Through a pilot test using vital sign data from a cohort of five patients, the limitations of a one-size-fits-all approach are demonstrated, thus highlighting the need for personalized treatment strategies. This study underscores the importance of adopting advanced technological approaches for ambulatory oxygen therapy.

Prospective clinical validation of the Empatica EmbracePlus wristband as a reflective pulse oximeter

Introduction

Respiratory diseases such as chronic obstructive pulmonary disease, obstructive sleep apnea syndrome, and COVID-19 may cause a decrease in arterial oxygen saturation (SaO2). The continuous monitoring of oxygen levels may be beneficial for the early detection of hypoxemia and timely intervention. Wearable non-invasive pulse oximetry devices measuring peripheral oxygen saturation (SpO2) have been garnering increasing popularity. However, there is still a strong need for extended and robust clinical validation of such devices, especially to address topical concerns about disparities in performances across racial groups. This prospective clinical validation aimed to assess the accuracy of the reflective pulse oximeter function of the EmbracePlus wristband during a controlled hypoxia study in accordance with the ISO 80601-2-61:2017 standard and the Food & Drug Administration (FDA) guidance.

Methods

Healthy adult participants were recruited in a controlled desaturation protocol to reproduce mild, moderate, and severe hypoxic conditions with SaO2 ranging from 100% to 70% (ClinicalTrials.gov registration #NCT04964609). The SpO2 level was estimated with an EmbracePlus device placed on the participant's wrist and the reference SaO2 was obtained from blood samples analyzed with a multiwavelength co-oximeter.

Results

The controlled hypoxia study yielded 373 conclusive measurements on 15 subjects, including 30% of participants with dark skin pigmentation (V-VI on the Fitzpatrick scale). The accuracy root mean square (Arms) error was found to be 2.4%, within the 3.5% limit recommended by the FDA. A strong positive correlation between the wristband SpO2 and the reference SaO2 was observed (r = 0.96, P < 0.001), and a good concordance was found with Bland-Altman analysis (bias, 0.05%; standard deviation, 1.66; lower limit, -4.7%; and upper limit, 4.8%). Moreover, acceptable accuracy was observed when stratifying data points by skin pigmentation (Arms 2.2% in Fitzpatrick V-VI, 2.5% in Fitzpatrick I-IV), and sex (Arms 1.9% in females, and 2.9% in males).

Discussion

This study demonstrates that the EmbracePlus wristband could be used to assess SpO2 with clinically acceptable accuracy under no-motion and high perfusion conditions for individuals of different ethnicities across the claimed range. This study paves the way for further accuracy evaluations on unhealthy subjects and during prolonged use in ambulatory settings.

Using Contactless Facial Image Recognition Technology to Detect Blood Oxygen Saturation

Since the outbreak of COVID-19, as of January 2023, there have been over 670 million cases and more than 6.8 million deaths worldwide. Infections can cause inflammation in the lungs and decrease blood oxygen levels, which can lead to breathing difficulties and endanger life. As the situation continues to escalate, non-contact machines are used to assist patients at home to monitor their blood oxygen levels without encountering others. This paper uses a general network camera to capture the forehead area of a person's face, using the RPPG (remote photoplethysmography) principle. Then, image signal processing of red and blue light waves is carried out. By utilizing the principle of light reflection, the standard deviation and mean are calculated, and the blood oxygen saturation is computed. Finally, the effect of illuminance on the experimental values is discussed. The experimental results of this paper were compared with a blood oxygen meter certified by the Ministry of Health and Welfare in Taiwan, and the experimental results had only a maximum error of 2%, which is better than the 3% to 5% error rates in other studies The measurement time was only 30 s, which is better than the one minute reported using similar equipment in other studies. Therefore, this paper not only saves equipment expenses but also provides convenience and safety for those who need to monitor their blood oxygen levels at home. Future applications can combine the SpO2 detection software with camera-equipped devices such as smartphones and laptops. The public can detect SpO2 on their own mobile devices, providing a convenient and effective tool for personal health management.

Photoplethysmographic Imaging of Hemodynamics and Two-Dimensional Oximetry

The review of recent papers devoted to actively developing methods of photoplethysmographic imaging (the PPGI) of blood volume pulsations in vessels and non-contact two-dimensional oximetry on the surface of a human body has been carried out. The physical fundamentals and technical aspects of the PPGI and oximetry have been considered. The manifold of the physiological parameters available for the analysis by the PPGI method has been shown. The prospects of the PPGI technology have been discussed. The possibilities of non-contact determination of blood oxygen saturation SpO2 (pulse saturation O2) have been described. The relevance of remote determination of the level of oxygenation in connection with the spread of a new coronavirus infection SARS-CoV-2 (COVID-19) has been emphasized. Most of the works under consideration cover the period 2010-2021.

Expression and Variations in EPAS1 Associated with Oxygen Metabolism in Sheep

Endothelial PAS domain protein 1 gene (EPAS1) is a member of the HIF gene family. This gene encodes a transcription factor subunit that is involved in the induction of oxygen-regulated genes. Several studies have demonstrated that a mutation in EPAS1 could affect oxygen sensing, polycythemia, and hemoglobin level. However, whether EPAS1 mutation affects sheep oxygen metabolism is still unknown. Therefore, we explored the relationship between the variation of EPAS1 and oxygen metabolism in sheep. In this study, variations in ovine EPAS1 exon 15 were investigated in 332 Tibetan sheep and 339 Hu sheep by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. In addition, we studied the effect of these variations on blood gas in 176 Tibetan sheep and 231 Hu sheep. Finally, the mRNA expression of EPAS1 in six tissues of Hu sheep and Tibetan sheep living at different altitudes (2500 m, 3500 m, and 4500 m) was analyzed by real-time quantitative PCR (RT-qPCR). Four alleles (A, B, C, and D) were detected, and their distributions highly differed between Tibetan sheep and Hu sheep. In Tibetan sheep, B was the dominant allele, and C and D alleles were rare, whereas all four alleles were common in Hu sheep. Six single nucleotide polymorphisms (SNPs) were identified between the four alleles and one of them was non-synonymous (p.F606L). While studying the blood gas levels in Tibetan sheep and Hu sheep, one variant region was found to be associated with an elevated pO₂ and sO₂, which suggested that variations in EPAS1 are associated with oxygen metabolism in sheep. RT-qPCR results showed that EPAS1 was expressed in the six tissues of Hu sheep and Tibetan sheep at different altitudes. In addition, the expression of EPAS1 in four tissues (heart, liver, spleen, and longissimus dorsi muscle) of Hu sheep was lower than that in Tibetan sheep from three different altitudes, and the expression of EPAS1 was positively correlated with the altitude. These results indicate that the variations and expression of EPAS1 is closely related to oxygen metabolism.

MsWH: A Multi-Sensory Hardware Platform for Capturing and Analyzing Physiological Emotional Signals

This paper presents a new physiological signal acquisition multi-sensory platform for emotion detection: Multi-sensor Wearable Headband (MsWH). The system is capable of recording and analyzing five different physiological signals: skin temperature, blood oxygen saturation, heart rate (and its variation), movement/position of the user (more specifically of his/her head) and electrodermal activity/bioimpedance. The measurement system is complemented by a porthole camera positioned in such a way that the viewing area remains constant. Thus, the user's face will remain centered regardless of its position and movement, increasing the accuracy of facial expression recognition algorithms. This work specifies the technical characteristics of the developed device, paying special attention to both the hardware used (sensors, conditioning, microprocessors, connections) and the software, which is optimized for accurate and massive data acquisition. Although the information can be partially processed inside the device itself, the system is capable of sending information via Wi-Fi, with a very high data transfer rate, in case external processing is required. The most important features of the developed platform have been compared with those of a proven wearable device, namely the Empatica E4 wristband, in those measurements in which this is possible.

3D Ultrasound-Guided Photoacoustic Imaging to Monitor the Effects of Suboptimal Tyrosine Kinase Inhibitor Therapy in Pancreatic Tumors

Pancreatic cancer is a disease with an incredibly poor survival rate. As only about 20% of patients are eligible for surgical resection, neoadjuvant treatments that can relieve symptoms and shrink tumors for surgical resection become critical. Many forms of treatments rely on increased vulnerability of cancerous cells, but tumors or regions within the tumors that may be hypoxic could be drug resistant. Particularly for neoadjuvant therapies such as the tyrosine kinase inhibitors utilized to shrink tumors, it is critical to monitor changes in vascular function and hypoxia to predict treatment efficacy. Current clinical imaging modalities used to obtain structural and functional information regarding hypoxia or oxygen saturation (StO₂) do not provide sufficient depth penetration or require the use of exogenous contrast agents. Recently, ultrasound-guided photoacoustic imaging (US-PAI) has garnered significant popularity, as it can noninvasively provide multiparametric information on tumor vasculature and function without the need for contrast agents. Here, we built upon existing literature on US-PAI and demonstrate the importance of changes in StO₂ values to predict treatment response, particularly tumor growth rate, when the outcomes are suboptimal. Specifically, we image xenograft mouse models of pancreatic adenocarcinoma treated with suboptimal doses of a tyrosine kinase inhibitor cabozantinib. We utilize the US-PAI data to develop a multivariate regression model that demonstrates that a therapy-induced reduction in tumor growth rate can be predicted with 100% positive predictive power and a moderate (58.33%) negative predictive power when a combination of pretreatment tumor volume and changes in StO₂ values pretreatment and immediately posttreatment was employed. Overall, our study indicates that US-PAI has the potential to provide label-free surrogate imaging biomarkers that can predict tumor growth rate in suboptimal therapy.

Breathability performance of antiviral cloth masks treated with silver nanoparticles for protection against COVID-19

The global widespread of coronavirus disease 2019 (COVID-19) has caused shortage of medical face masks and led to developing of various types of cloth masks with different levels of protection and comfort to meet the market demands. Breathing comfort is a significant aspect that should be considered during the design of cloth masks along with the filtration efficiency; otherwise, the wearer will feel suffocated. In this work, different types of cotton and polyester knitted fabrics blended with spandex yarns were produced and treated with silver nanoparticles to be used as antiviral cloth masks. Scanning electron microscope, transmission electron microscope, and EDX were used to characterize the silver nanoparticles (AgNPs). Antiviral activity was assessed against SARS-CoV-2 coronavirus as well. The influence of using different fabric materials, number of layers, and hybrid layers on their air permeability and breathability were investigated to evaluate the comfortability of the cloth masks. Physiological impacts of wearing the cloth masks were evaluated by measuring oxygen saturation of hemoglobin and heart rate of the wearers while doing various activities. The results indicated that AgNPs have low cytotoxicity and considerable efficiency in inhibition of SARS-CoV-2. Adding spandex yarns with different count and ratios reduced the porosity and air permeability of the fabrics. Moreover, the combination of three hybrid layers' mask made of polyester fabric in the outer layer with 100% cotton fabric in the inner layer showed high comfortability associated with high air permeability and breathability. Also, wearing these masks while doing activities showed no significant effect on blood oxygen saturation and heart rate of the wearers.

Hypertension in Children with Obstructive Sleep Apnea Syndrome-Age, Weight Status, and Disease Severity

Older age, obesity, and obstructive sleep apnea syndrome (OSAS) are known to increase the risk of hypertension in adults. However, data for children are scarce. This study aimed to investigate the relationships between hypertension, age, weight status, and disease severity in 396 children with OSAS. The prevalence rates of hypertension, obesity, and severe OSAS (apnea-hypopnea index ≥10) were 27.0%, 28.0%, and 42.9%, respectively. Weight z-score and apnea-hypopnea index were independently correlated with systolic blood pressure z-score, and minimal blood oxygen saturation (SpO₂) was independently associated with diastolic blood pressure z-score. Overall, late childhood/adolescence (odds ratio (OR) = 1.72, 95% CI = 1.05–2.81), obesity (OR, 2.58, 95% CI = 1.58–4.22), and severe OSAS (OR = 2.38, 95% CI = 1.48–3.81) were independent predictors of pediatric hypertension. Furthermore, late childhood/adolescence (OR = 2.50, 95% CI = 1.10–5.71) and abnormal SpO₂ (mean SpO₂ < 95%; OR = 4.91, 95% CI = 1.81–13.27) independently predicted hypertension in obese children, and severe OSAS (OR = 2.28, 95% CI = 1.27–4.10) independently predicted hypertension in non-obese children. In conclusion, obesity, OSAS severity, and abnormal SpO₂ are potentially modifiable targets to improve hypertension while treating children with OSAS.

Flexible Wearable Sensors for Cardiovascular Health Monitoring

Cardiovascular diseases account for the highest mortality globally, but recent advances in wearable technologies may potentially change how these illnesses are diagnosed and managed. In particular, continuous monitoring of cardiovascular vital signs for early intervention is highly desired. To this end, flexible wearable sensors that can be comfortably worn over long durations are gaining significant attention. In this review, advanced flexible wearable sensors for monitoring cardiovascular vital signals are outlined and discussed. Specifically, the functional materials, configurations, mechanisms, and recent advances of these flexible sensors for heart rate, blood pressure, blood oxygen saturation, and blood glucose monitoring are highlighted. Different mechanisms in bioelectric, mechano-electric, optoelectric, and ultrasonic wearable sensors are presented to monitor cardiovascular vital signs from different body locations. Present challenges, possible strategies, and future directions of these wearable sensors are also discussed. With rapid development, these flexible wearable sensors will potentially be applicable for both medical diagnosis and daily healthcare use in tackling cardiovascular diseases.

Predictors of Hypoxemia and Related Adverse Outcomes in Patients Hospitalized with COVID-19: A Double-Center Retrospective Study

Hypoxemia is a hallmark of coronavirus disease 2019 (COVID-19) severity. We sought to determine predictors of hypoxemia and related adverse outcomes among patients hospitalized with COVID-19 in the two largest hospitals in Jerusalem, Israel, from 9 March through 16 July 2020. Patients were categorized as those who developed reduced (<94%) vs. preserved (≥94%) arterial oxygen saturation (SpO₂) within the first 48 h after arrival to the emergency department. Overall, 492 hospitalized patients with COVID-19 were retrospectively analyzed. Patients with reduced SpO₂ were significantly older, had more comorbidities, higher body surface area (BSA) and body mass index (BMI), lower lymphocyte counts, impaired renal function, and elevated liver enzymes, c-reactive protein (CRP), and D-dimer levels as compared to those with preserved SpO₂. In the multivariable regression analysis, older age (odds ratio (OR) 1.02 per year, p < 0.001), higher BSA (OR 1.16 per 0.10 m², p = 0.003) or BMI (OR 1.05 per 1 kg/m², p = 0.011), lower lymphocyte counts (OR 1.72 per 1 × 10³/μL decrease, p = 0.002), and elevated CRP (1.11 per 1 mg/dL increase, p < 0.001) were found to be independent predictors of low SpO₂. Severe hypoxemia requiring ventilatory support, older age, and pre-existing comorbidities, including underlying renal dysfunction and heart failure, were found to be significantly associated with in-hospital mortality. These findings suggest that assessment of predictors of hypoxemia early at the time of hospitalization with COVID-19 may be helpful in risk stratification and management.

Multiple illumination learned spectral decoloring for quantitative optoacoustic oximetry imaging

SIGNIFICANCE

Quantitative measurement of blood oxygen saturation (sO2) with optoacoustic (OA) imaging is one of the most sought after goals of quantitative OA imaging research due to its wide range of biomedical applications.

AIM

A method for accurate and applicable real-time quantification of local sO2 with OA imaging.

APPROACH

We combine multiple illumination (MI) sensing with learned spectral decoloring (LSD). We train LSD feedforward neural networks and random forests on Monte Carlo simulations of spectrally colored absorbed energy spectra, to apply the trained models to real OA measurements. We validate our combined MI-LSD method on a highly reliable, reproducible, and easily scalable phantom model, based on copper and nickel sulfate solutions.

RESULTS

With this sulfate model, we see a consistently high estimation accuracy using MI-LSD, with median absolute estimation errors of 2.5 to 4.5 percentage points. We further find fewer outliers in MI-LSD estimates compared with LSD. Random forest regressors outperform previously reported neural network approaches.

CONCLUSIONS

Random forest-based MI-LSD is a promising method for accurate quantitative OA oximetry imaging.

Photoplethysmography behind the Ear Outperforms Electrocardiogram for Cardiovascular Monitoring in Dynamic Environments

An increasing proportion of occupational mishaps in dynamic, high-risk operational environments have been attributed to human error, yet there are currently no devices to routinely provide accurate physiological data for insights into underlying contributing factors. This is most commonly due to limitations of commercial and clinical devices for collecting physiological data in environments of high motion. Herein, a novel Photoplethysmography (PPG) sensor device was tested, called SPYDR (Standalone Performance Yielding Deliberate Risk), reading from a behind-the-ear location, specifically designed for high-fidelity data collection in highly dynamic high-motion, high-pressure, low-oxygen, and high-G-force environments. For this study, SPYDR was installed as a functional ear-cup replacement in flight helmets worn by rated US Navy aircrew. Subjects were exposed to reduced atmospheric pressure using a hypobaric chamber to simulated altitudes of 25,000 feet and high G-forces in a human-rated centrifuge up to 9 G acceleration. Data were compared to control devices, finger and forehead PPG sensors, and a chest-mounted 12-lead ECG. SPYDR produced high-fidelity data compared to controls with little motion-artifact controls in the no-motion environment of the hypobaric chamber. However, in the high-motion, high-force environment of the centrifuge, SPYDR recorded consistent, accurate data, whereas PPG controls and ECG data were unusable due to a high-degree-motion artifacts. The data demonstrate that SPYDR provides an accurate and reliable system for continuous physiological monitoring in high-motion, high-risk environments, yielding a novel method for collecting low-artifact cardiovascular assessment data important for investigating currently inaccessible parameters of human physiology.

Effects of Tai Chi and running on blood oxygen saturation: a pilot study

OBJECTIVES

Large drops in blood oxygen saturation (SpO2) to levels as low as 84% was observed following Tai Chi practice, during a study on the effects of Tai Chi on SpO2. The objectives of the current pilot study were to determine if this was a statistically significant drop, and how SpO2 levels compared to an aerobic activity such as running, in pre, concurrent, and post measurements.

METHODS

Repeated measures of blood oxygen saturation (SpO2) were taken of a 50-year-old male before, during and for 1 min after TC and running.

RESULTS

Measurements of SpO2 before, during, and after TC resulted in a statistically significant increase in SpO2 during TC (p=1.69e-06), and a statistically significant (p=1.71e-06) brief momentary drop from resting levels, as low as 87% SpO2. Running showed no significant change in pre and post levels, with a significant change and decrease in SpO2 during running (p=1.1e-08), suggesting increased oxygen use by the large muscle groups during exercise. SpO2 returned to normal resting levels following running with no post drop. Results suggest a higher rate of oxygen metabolism during TC, with a potential effect on hypoxic (oxygen deficient) areas of the body.

CONCLUSIONS

Findings suggest direct and unique effects on enhanced blood oxygen saturation and oxygen metabolism, which may underlie benefits for conditions complicated by hypoxia, including cardiopulmonary disease, immunity, chronic pain, and arthritis.

Design Implementation and Evaluation of a Mobile Continuous Blood Oxygen Saturation Monitoring System

Objective: In this study, we built a mobile continuous Blood Oxygen Saturation (SpO2) monitor, and for the first time, explored key design principles towards daily applications. Methods: We firstly built a customized wearable computer that can sense two-channel photoplethysmogram (PPG) signals, and transmit the signals wirelessly to smartphone. Afterwards, we explored many SpO2 model building principles, focusing on linear/nonlinear models, different PPG parameter calculation methods, and different finger types. Moreover, we further compared PPG sensor placement principles by comparing different hand configurations and different finger configurations. Finally, a dataset collected from eleven human subjects was used to evaluate the mobile health monitor and explore all of the above design principles. Results: The experimental results show that the root mean square error of the SpO2 estimation is only 1.8, indicating the effectiveness of the system. Conclusion: These results indicate the effectiveness of the customized mobile SpO2 monitor and the selected design principles. Significance: This research is expected to facilitate the continuous SpO2 monitoring of patients with clinical indications.

Admission oxygen saturation and all-cause in-hospital mortality in acute myocardial infarction patients: data from the MIMIC-III database

Background

Acute myocardial infarction (AMI) is mainly caused by a mismatch of blood oxygen supply and demand in the myocardium. However, several studies have suggested that excessively high or low arterial oxygen tension could have deleterious effects on the prognosis of AMI patients. Therefore, the relationship between blood oxygenation and clinical outcomes among AMI patients is unclear, and could be nonlinear. In the critical care setting, blood oxygen level is commonly measured continuously using pulse oximetry-derived oxygen saturation (SpO₂). The present study aimed to determine the association between admission SpO₂ levels and all-cause in-hospital mortality, and to elucidate the optimal SpO₂ range with real-world data.

Methods

Patients diagnosed with AMI on admission in the Medical Information Mart for Intensive Care III (MIMIC-III) database were included. A generalized additive model (GAM) with loess smoothing functions was used to determine and visualize the nonlinear relationship between admission SpO₂ levels within the first 24 hours after ICU admission and mortality. Moreover, the Cox regression model was constructed to confirm the association between SpO₂ and mortality.

Results

We included 1,846 patients who fulfilled our inclusion criteria, among whom 587 (31.80%) died during hospitalization. The GAM showed that the relationship between admission SpO₂ levels and all-cause in-hospital mortality among AMI patients was nonlinear, as a U-shaped curve was observed. In addition, the lowest mortality was observed for an SpO₂ range of 94–96%. Adjusted multivariable Cox regression analysis confirmed that the admission SpO₂ level of 94–96% was independently associated with decreased mortality compared to SpO₂ levels <94% [hazard ratio (HR) 1.352; 95% confidence interval (CI): 1.048–1.715; P=0.028] and >96% (HR 1.315; 95% CI: 1.018–1.658; P=0.030).

Conclusions

The relationship between admission SpO₂ levels and all-cause in-hospital mortality followed a U-shaped curve among patients with AMI. The optimal oxygen saturation range was identified as an SpO₂ range of 94–96%, which was independently associated with increased survival in a large and heterogeneous cohort of AMI patients.

Retinal blood oxygen saturation and vascular endothelial growth factor-A in early diabetic retinopathy: A protocol for systematic review and meta-analysis

BACKGROUND

Diabetic retinopathy (DR) remains the most common microvascular complication of diabetes; both its high prevalence and associated high risk of vision loss lead it to the major global health burden. Despite significant research efforts, there still remains much of the underlying pathology not fully understand. In the past studies, inner retinal blood flow disturbances are widely assessed as a potential biomarker of DR. However, the results have been variable and even contradictory. Improved methods to figure out the metabolic disturbances associated with DR are essential. Some research showed that both vascular endothelial growth factor-A and blood oxygen saturation are higher in DR patients and correlated with disease severity. Therefore, we decided to conduct a systematic review and meta-analysis to find out the connection of them and provide robust evidence on the mechanism underlying this connection to help us better understand the pathophysiology behind the hypoxic retina and find better ways to treat DR.

METHODS

This study will be conducted according to Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols. We will do electronic searches from PubMed, EMBASE, Web of Science, Cochrane Library, Wanfang database, CNKI, and VIP database. Two reviewers will screen all the references independently and any disagreement will be solved by the third involvement. All data will be extracted by 2 independent reviewers according to a standardized data extraction sheet. Based on the type of studies, 2 reviewers will independently use different scales to assess the risk of bias. Any disagreements and conflicts will be resolved by discussing it with a third reviewer. We will conduct a random-effects meta-analysis. Individual and pooled odds ratios/relative risks and associated 95% confidence intervals will be calculated as well as between-study heterogeneity. The potential for publication bias will also be evaluated. If possible, we will explore reasons for potential between-study heterogeneity.

RESULTS

This study is a protocol for systematic review and meta-analysis without results. Associated data analysis will be carried out after the protocol.

CONCLUSION

The protocol aims to guide a meta-analysis whose purpose is investigating the association between retinal blood oxygen saturation and vascular endothelial growth factors in patients with early DR and trying to find out the mechanism that the changing of retinal oxygen saturation in patients with DR.

INPLASY REGISTRATION NUMBER

INPLASY202040161.

Wave of single-impulse-stimulated fast initial dip in single vessels of mouse brains imaged by high-speed functional photoacoustic microscopy

SIGNIFICANCE

The initial dip in hemoglobin-oxygenation response to stimulations is a spatially confined endogenous indicator that is faster than the blood flow response, making it a desired label-free contrast to map the neural activity. A fundamental question is whether a single-impulse stimulus, much shorter than the response delay, could produce an observable initial dip without repeated stimulation.

AIM

To answer this question, we report high-speed functional photoacoustic (PA) microscopy to investigate the initial dip in mouse brains.

APPROACH

We developed a Raman-laser-based dual-wavelength functional PA microscope that can image capillary-level blood oxygenation at a 1-MHz one-dimensional imaging rate. This technology was applied to monitor the hemodynamics of mouse cerebral vasculature after applying an impulse stimulus to the forepaw.

RESULTS

We observed a transient initial dip in cerebral microvessels starting as early as 0.13 s after the onset of the stimulus. The initial dip and the subsequent overshoot manifested a wave pattern propagating across different microvascular compartments.

CONCLUSIONS

We quantified both spatially and temporally the single-impulse-stimulated microvascular hemodynamics in mouse brains at single-vessel resolution. Fast label-free imaging of single-impulse response holds promise for real-time brain-computer interfaces.

Role of Blood Oxygen Saturation During Post-Natal Human Cardiomyocyte Cell Cycle Activities

Blood oxygen saturation (SaO₂) is one of the most important environmental factors in clinical heart protection. This study used human heart samples and human induced pluripotent stem cell-cardiomyocytes (iPSC-CMs) to assess how SaO₂ affects human CM cell cycle activities. The results showed that there were significantly more cell cycle markers in the moderate hypoxia group (SaO₂: 75% to 85%) than in the other 2 groups (SaO₂ <75% or >85%). In iPSC-CMs 15% and 10% oxygen (O₂) treatment increased cell cycle markers, whereas 5% and rapid change of O₂ decreased the markers. Moderate hypoxia is beneficial to the cell cycle activities of post-natal human CMs.

Opto-acoustic imaging of relative blood oxygen saturation and total hemoglobin for breast cancer diagnosis

Opto-acoustic imaging involves using light to produce sound waves for visualizing blood in biological tissue. By using multiple optical wavelengths, diagnostic images of blood oxygen saturation and total hemoglobin are generated using endogenous optical contrast, without injection of any external contrast agent and without using any ionizing radiation. The technology has been used in recent clinical studies for diagnosis of breast cancer to help distinguish benign from malignant lesions, potentially reducing the need for biopsy through improved diagnostic imaging accuracy. To enable this application, techniques for mapping oxygen saturation differences within tissue are necessary. Using biologically relevant opto-acoustic phantoms, we analyze the ability of an opto-acoustic imaging system to display colorized parametric maps that are generated using a statistical mapping approach. To mimic breast tissue, a material with closely matching properties for optical absorption, optical scattering, acoustic attenuation, and speed of sound is used. The phantoms include two vessels filled with whole blood at oxygen saturation levels determined using a sensor-based approach. A flow system with gas-mixer and membrane oxygenator adjusts the oxygen saturation of each vessel independently. Datasets are collected with an investigational Imagio^® breast imaging system. We examine the ability to distinguish vessels as the oxygen saturation level and imaging depth are varied. At depth of 15 mm and hematocrit of 42%, a sufficient level of contrast to distinguish between two 1.6-mm diameter vessels was measured for an oxygen saturation difference of ∼4.6  %  . In addition, an oxygenated vessel was visible at a depth of 48 mm using an optical wavelength of 1064 nm, and a deoxygenated vessel was visible to a depth of 42 mm with 757 nm. The results provide insight toward using color mapped opto-acoustic images for diagnosing breast cancer.

Estimating blood oxygenation from photoacoustic images: can a simple linear spectroscopic inversion ever work?

Linear spectroscopic inversions, in which photoacoustic amplitudes are assumed to be directly proportional to absorption coefficients, are widely used in photoacoustic imaging to estimate blood oxygen saturation because of their simplicity. Unfortunately, they do not account for the spatially varying wavelength-dependence of the light fluence within the tissue, which introduces "spectral coloring," a potentially significant source of error. However, accurately correcting for spectral coloring is challenging, so we investigated whether there are conditions, e.g., sets of wavelengths, where it is possible to ignore the spectral coloring and still obtain accurate oxygenation measurements using linear inversions. Accurate estimates of oxygenation can be obtained when the wavelengths are chosen to (i) minimize spectral coloring, (ii) avoid ill-conditioning, and (iii) maintain a sufficiently high signal-to-noise ratio (SNR) for the estimates to be meaningful. It is not obvious which wavelengths will satisfy these conditions, and they are very likely to vary for different imaging scenarios, making it difficult to find general rules. Through the use of numerical simulations, we isolated the effect of spectral coloring from sources of experimental error. It was shown that using wavelengths between 500 nm and 1000 nm yields inaccurate estimates of oxygenation and that careful selection of wavelengths in the 620- to 920-nm range can yield more accurate oxygenation values. However, this is only achievable with a good prior estimate of the true oxygenation. Even in this idealized case, it was shown that considerable care must be exercised over the choice of wavelengths when using linear spectroscopic inversions to obtain accurate estimates of blood oxygenation. This suggests that for a particular imaging scenario, obtaining accurate and reliable oxygenation estimates using linear spectroscopic inversions requires careful modeling or experimental studies of that scenario, taking account of the instrumentation, tissue anatomy, likely sO₂ range, and image formation process.

The Search for Optimal Oxygen Saturation Targets in Critically Ill Patients: Observational Data From Large ICU Databases

BACKGROUND

Although low oxygen saturations are generally regarded as deleterious, recent studies in ICU patients have shown that a liberal oxygen strategy increases mortality. However, the optimal oxygen saturation target remains unclear. The goal of this study was to determine the optimal range by using real-world data.

METHODS

Replicate retrospective analyses were conducted of two electronic medical record databases: the eICU Collaborative Research Database (eICU-CRD) and the Medical Information Mart for Intensive Care III database (MIMIC). Only patients with at least 48 h of oxygen therapy were included. Nonlinear regression was used to analyze the association between median pulse oximetry-derived oxygen saturation (Spo₂) and hospital mortality. We derived an optimal range of Spo₂ and analyzed the association between the percentage of time within the optimal range of Spo₂ and hospital mortality. All models adjusted for age, BMI, sex, and Sequential Organ Failure Assessment score. Subgroup analyses included ICU types, main diagnosis, and comorbidities.

RESULTS

The analysis identified 26,723 patients from eICU-CRD and 8,564 patients from MIMIC. The optimal range of Spo₂ was 94% to 98% in both databases. The percentage of time patients were within the optimal range of Spo₂ was associated with decreased hospital mortality (OR of 80% vs 40% of the measurements within the optimal range, 0.42 [95% CI, 0.40-0.43] for eICU-CRD and 0.53 [95% CI, 0.50-0.55] for MIMIC). This association was consistent across subgroup analyses.

CONCLUSIONS

The optimal range of Spo₂ was 94% to 98% and should inform future trials of oxygen therapy.

[Development of a Portable Pulse Oxymetry Simulator System]

This article describes the design of a portable blood oxygen simulation system that can be used to simulate various blood gas saturation states of the human body. The system can be used to simulate various states of blood gas saturation, and can also simulate large blood oxygen saturation dynamic range, pulse rate range and perfusion index range. It can be used for testing, but not for clinical examination instruments. Moreover, the system has the characteristics of small size and low cost compared with the commercial blood oxygen simulator. Although the simulation system is not directly used for the detection of blood gas saturation of patients, it is also an essential equipment in the production and testing process, so it has certain practical value.

Randomised cross-over study of automated oxygen control for preterm infants receiving nasal high flow

OBJECTIVE

To evaluate a prototype automated controller (IntellO₂) of the inspired fraction of oxygen (FiO₂) in maintaining a target range of oxygen saturation (SpO₂) in preterm babies receiving nasal high flow (HF) via the Vapotherm Precision Flow.

DESIGN

Prospective two-centre order-randomised cross-over study.

SETTING

Neonatal intensive care units.

PATIENTS

Preterm infants receiving HF with FiO₂ ≥25%.

INTERVENTION

Automated versus manual control of FiO₂ to maintain a target SpO₂ range of 90%-95% (or 90%-100% if FiO₂=21%).

MAIN OUTCOME MEASURES

The primary outcome measure was per cent of time spent within target SpO₂ range. Secondary outcomes included the overall proportion and durations of SpO₂ within specified hyperoxic and hypoxic ranges and the number of in-range episodes per hour.

RESULTS

Data were analysed from 30 preterm infants with median (IQR) gestation at birth of 26 (24-27) weeks, study age of 29 (18-53) days and study weight 1080 (959-1443) g. The target SpO₂ range was achieved 80% of the time on automated (IntellO₂) control (IQR 70%-87%) compared with 49% under manual control (IQR 40%-57%; p<0.0001). There were fewer episodes of SpO₂ below 80% lasting at least 60 s under automated control (0 (IQR 0-1.25)) compared with manual control (5 (IQR 2.75-14)). There were no differences in the number of episodes per hour of SpO₂ above 98% (4.5 (IQR 1.8-8.5) vs 5.5 (IQR 1.9-14); p=0.572) between the study arms.

CONCLUSIONS

The IntellO₂ automated oxygen controller maintained patients in the target SpO₂ range significantly better than manual adjustments in preterm babies receiving HF.

TRIAL REGISTRATION NUMBER

NCT02074774.

Three-dimensional quantitative photoacoustic tomography using an adjoint radiance Monte Carlo model and gradient descent

Quantitative photoacoustic tomography aims to recover maps of the local concentrations of tissue chromophores from multispectral images. While model-based inversion schemes are promising approaches, major challenges to their practical implementation include the unknown fluence distribution and the scale of the inverse problem. We describe an inversion scheme based on a radiance Monte Carlo model and an adjoint-assisted gradient optimization that incorporates fluence-dependent step sizes and adaptive moment estimation. The inversion is shown to recover absolute chromophore concentrations, blood oxygen saturation, and the Grüneisen parameter from in silico three-dimensional phantom images for different radiance approximations. The scattering coefficient is assumed to be homogeneous and known a priori.

Sevoflurane Inhalation Anesthesia for Uncooperative Pediatric Outpatients in the Treatment of Ankyloglossia: A Retrospective Study of 137 Cases

Background: To retrospectively assess the efficacy and safety of sevoflurane inhalation anesthesia for the treatment of ankyloglossia on uncooperative pediatric outpatients. Methods: Pediatric patients with ankyloglossia (Degree 3 to Degree 5, coarse or thick) were enrolled in this retrospective analysis. The treatment of ankyloglossia was conducted with sevoflurane induction (8%) and maintenance (2%-3%) continuously with nasal cannula. Heart rate, respiratory rate, electrocardiogram, blood pressure, and peripheral blood oxygen saturation were monitored continuously during operations. Onset time, recovery time, adverse complications were recorded until Aldrete score was ≥ 9. Patients were followed up 24 h, 1 and 2 weeks after operation. Results: One hundred and thirty-seven children completed surgeries with ideal anesthesia status. The operation duration were 10-20 minutes (15.15 ± 2.04), and the children woke up in 10-30 minutes (18.95 ± 3.91). The average intra-operative blood oxygen saturation were lower than preoperative ones (p = .005). Adverse effects were 13.1%, including 3 (2.2%) respiratory depression (SpO₂ < 90%), 11 (8.0%) dysphoria and crying during recovery, 2 (1.5%) transient fever symptom. Conclusions: Sevoflurane inhalation anesthesia in the treatment of ankyloglossia resulted in rapid onset and recovery, with few adverse reactions and significant clinical efficacy, and was suited to uncooperative pediatric outpatients.

Spectral correction for handheld optoacoustic imaging by means of near-infrared optical tomography in reflection mode

In vivo imaging of tissue/vasculature oxygen saturation levels is of prime interest in many clinical applications. To this end, the feasibility of combining two distinct and complementary imaging modalities is investigated: optoacoustics (OA) and near-infrared optical tomography (NIROT), both operating noninvasively in reflection mode. Experiments were conducted on two optically heterogeneous phantoms mimicking tissue before and after the occurrence of a perturbation. OA imaging was used to resolve submillimetric vessel-like optical absorbers at depths up to 25 mm, but with a spectral distortion in the OA signals. NIROT measurements were utilized to image perturbations in the background and to estimate the light fluence inside the phantoms at the wavelength pair (760 nm, 830 nm). This enabled the spectral correction of the vessel-like absorbers' OA signals: the error in the ratio of the absorption coefficient at 830 nm to that at 760 nm was reduced from 60%-150% to 10%-20%. The results suggest that oxygen saturation (SO ₂ ) levels in arteries can be determined with <10% error and furthermore, that relative changes in vessels' SO ₂ can be monitored with even better accuracy. The outcome relies on a proper identification of the OA signals emanating from the studied vessels.

The Role of Duration of Hyperbaric Oxygen Therapy on Lung Injury: An Experimental Study Lung Injury and Hyperbaric Oxygen Therapy

OBJECTIVES

We aim to histopathologically analyze the effect of hyperbaric oxygen (HBO) therapy in the lung tissue.

MATERIAL AND METHODS

A total of 21 rabbits were divided into three groups, with each containing seven rabbits. Group 1 was the control group. Group 2 underwent HBO of 3 atmosphere absolute (ATA) for 90 min/day for 7 days. In group 3, HBO at 3 ATA was administered 90 min/day for 28 days. Oxygen saturation (SpO₂) was determined by pulse oximetry before and after administration of HBO. Rabbits were sacrificed, and the apex of the right lung was excised.

RESULTS

SpO₂ was 98-100% in all rabbits before HBO administration. After the procedure, the mean SpO₂ was 92% and 83% in groups 2 and 3, respectively. As expected, histopathologic examination in group 1 was normal. In group 2, congestion in the lung vessels, mononuclear cell infiltration in the bronchial mucosa, interstitial edema, and alveolar dilation were evident. Histopathologic examination in group 3 indicated diffuse alveolar edema, peribronchial mononuclear cell infiltration, thickening of the alveolar and vessel wall, and intraalveolar hemorrhage.

CONCLUSION

There is a strict relationship between duration of HBO administration and severity of lung injury.

Determination of optical properties, drug concentration, and tissue oxygenation in human pleural tissue before and after Photofrin-mediated photodynamic therapy

PDT efficacy depends on the concentration of photosensitizer, oxygen, and light delivery in patient tissues. In this study, we measure the in-vivo distribution of important dosimetric parameters, namely the tissue optical properties (absorption μ_a (λ) and scattering μ_s ' (λ) coefficients), photofrin concentration (c_photofrin), blood oxygen saturation (%S_tO₂), and total hemoglobin concentration (THC), before and after PDT. We characterize the inter- and intra-patient heterogeneity of these quantities and explore how these properties change as a result of PDT treatment. The result suggests the need for real-time dosimetry during PDT to optimize the treatment condition depending on the optical and physiological properties.

Sex-linked difference in blood oxygen saturation

BACKGROUND

It is not known whether SpO₂ in healthy volunteers is affected by sex.

OBJECTIVE

To evaluate whether there are differences in SpO₂ between young healthy adult males and females and to evaluate whether the differences are already present at birth.

METHODS

We studied two cohorts of patients. The first one consisted of young adult volunteers (105 males and 102 females). In these patients, SpO₂ was measured as well as selected anthropometric variables (height, weight), vital signs (respiratory rate, pulse rate and body temperature) and obtained data on menstrual cycle phase of the female participants. For the second cohort, we reanalyzed data from a previous prospective study that was performed to compare SpO₂ of newborns infants born at different altitudes (sea level or 760 m above sea level).

MEASUREMENTS AND MAIN RESULTS

In young male adults, mean SpO₂ was 97.1% ± 1.2% versus 98.6% ± 1.0% in females (P < .001). This difference remained significant (P = .002) after correction for BMI, BSA and age, variables that were significantly different between sexes in univariate analysis. The SpO₂ in females was unaffected by menstrual phase. In contrast to findings in adults, there were no significant differences in SpO₂ measurements in newborn infants attributable to sex.

CONCLUSIONS

Healthy young female adults have a higher (1.5%) SpO₂ than their male counterparts. This difference is not yet present at birth. Further studies are needed to determine the timing of sex-differences, and to better define the mechanism(s) behind this observation.

Nocturnal Oximetry-based Evaluation of Habitually Snoring Children

RATIONALE

The vast majority of children around the world undergoing adenotonsillectomy for obstructive sleep apnea-hypopnea syndrome (OSA) are not objectively diagnosed by nocturnal polysomnography because of access availability and cost issues. Automated analysis of nocturnal oximetry (nSp_O2), which is readily and globally available, could potentially provide a reliable and convenient diagnostic approach for pediatric OSA.

METHODS

Deidentified nSp_O2 recordings from a total of 4,191 children originating from 13 pediatric sleep laboratories around the world were prospectively evaluated after developing and validating an automated neural network algorithm using an initial set of single-channel nSp_O2 recordings from 589 patients referred for suspected OSA.

MEASUREMENTS AND MAIN RESULTS

The automatically estimated apnea-hypopnea index (AHI) showed high agreement with AHI from conventional polysomnography (intraclass correlation coefficient, 0.785) when tested in 3,602 additional subjects. Further assessment on the widely used AHI cutoff points of 1, 5, and 10 events/h revealed an incremental diagnostic ability (75.2, 81.7, and 90.2% accuracy; 0.788, 0.854, and 0.913 area under the receiver operating characteristic curve, respectively).

CONCLUSIONS

Neural network-based automated analyses of nSp_O2 recordings provide accurate identification of OSA severity among habitually snoring children with a high pretest probability of OSA. Thus, nocturnal oximetry may enable a simple and effective diagnostic alternative to nocturnal polysomnography, leading to more timely interventions and potentially improved outcomes.

Automated Screening of Children With Obstructive Sleep Apnea Using Nocturnal Oximetry: An Alternative to Respiratory Polygraphy in Unattended Settings

STUDY OBJECTIVES

Nocturnal oximetry has become known as a simple, readily available, and potentially useful diagnostic tool of childhood obstructive sleep apnea (OSA). However, at-home respiratory polygraphy (HRP) remains the preferred alternative to polysomnography (PSG) in unattended settings. The aim of this study was twofold: (1) to design and assess a novel methodology for pediatric OSA screening based on automated analysis of at-home oxyhemoglobin saturation (SpO₂), and (2) to compare its diagnostic performance with HRP.

METHODS

SpO₂ recordings were parameterized by means of time, frequency, and conventional oximetric measures. Logistic regression models were optimized using genetic algorithms (GAs) for three cutoffs for OSA: 1, 3, and 5 events/h. The diagnostic performance of logistic regression models, manual obstructive apnea-hypopnea index (OAHI) from HRP, and the conventional oxygen desaturation index ≥ 3% (ODI3) were assessed.

RESULTS

For a cutoff of 1 event/h, the optimal logistic regression model significantly outperformed both conventional HRP-derived ODI3 and OAHI: 85.5% accuracy (HRP 74.6%; ODI3 65.9%) and 0.97 area under the receiver operating characteristics curve (AUC) (HRP 0.78; ODI3 0.75) were reached. For a cutoff of 3 events/h, the logistic regression model achieved 83.4% accuracy (HRP 85.0%; ODI3 74.5%) and 0.96 AUC (HRP 0.93; ODI3 0.85) whereas using a cutoff of 5 events/h, oximetry reached 82.8% accuracy (HRP 85.1%; ODI3 76.7) and 0.97 AUC (HRP 0.95; ODI3 0.84).

CONCLUSIONS

Automated analysis of at-home SpO₂ recordings provide accurate detection of children with high pretest probability of OSA. Thus, unsupervised nocturnal oximetry may enable a simple and effective alternative to HRP and PSG in unattended settings.

[Effect of intravenous injection of intravenous injection of chlorine on blood oxygen saturation in patients with nasal endoscopic surgery]

Objective:To observe the effect of intravenous injection of chlorine on postoperative analgesia and blood oxygen saturation in patients with nasal endoscopic surgery.Method:According to the standard of American Society of anesthesiologists(ASA) grading assessment for Ⅰ-Ⅱ, undergoing nasal endoscopic surgery of 120 patients were randomly divided into two groups, 60 cases in each group. Control group dezocine 0.8 g/kg+ physiological saline to 100 ml; on the basis of the experimental group with flurbiprofen 2 mg/kg+ physiological saline to 100 ml. Respectively in the postoperative recovery and postoperative 2, 4, 12, 24 and 48 h recording vital signs, pain scores(visual analogue score, VAS) and sedation score(Ramsay score) and observe the adverse reaction rate and patient surveys on the satisfaction of postoperative analgesia.Result:The two groups compared test of TKA group after 4, 8, 12, 24, 36 h, 48 h, 72 h resting VAS score and postoperative 24 h, 48 h, 72 h activities of VAS score were lower than the control group, the difference is statistically significant (F=1 873.26, P< 0.05). After 2 h, 6 h, 2 groups of pH, PaO₂, PaCO₂, SpO₂ compared statistically significant (P> 0.05). After 24h, 48h after test group, PaO₂, PaCO₂, SpO₂ is better than that of the control group(P< 0.05); after 6 h, 24 h, 48 h after the test group patients Ramsay Sedation score than the control group, the difference is statistically significant(F=1 031.35, P< 0.05). The experimental group after TKA patients of pain control education satisfaction and to control or reduce pain method of satisfaction were superior to the control group, the difference significant (χ²=11.02, P< 0.05;χ²=9.33, P< 0.05).Conclusion:The application of intravenous injection of intravenous injection of chlorine in the postoperative pain of nasal endoscopic surgery can significantly improve the analgesic effect, improve the blood gas analysis, improve the analgesic effect, it is worthy of popularization and application.

Effects of Breast Milk and Vanilla Odors on Premature Neonate's Heart Rate and Blood Oxygen Saturation During and After Venipuncture

BACKGROUND

Different studies have shown that the use of olfactory stimuli during painful medical procedures reduces infants' response to pain. The main purpose of the current study was to investigate the effect of breast milk odor and vanilla odor on premature infants' vital signs including heart rate and blood oxygen saturation during and after venipuncture.

METHODS

A total of 135 preterm infants were randomly selected and divided into three groups of control, vanilla odor, and breast milk odor. Infants in the breast milk group and the vanilla group were exposed to breast milk odor and vanilla odor from 5 minutes prior to sampling until 30 seconds after sampling.

RESULTS

The results showed that breast milk odor has a significant effect on the changes of neonatal heart rate and blood oxygen saturation during and after venipuncture and decreased the variability of premature infants' heart rate and blood oxygen saturation. Vanilla odor has no significant effect on premature infants' heart rate and blood oxygen saturation.

CONCLUSION

Breast milk odor can decrease the variability of premature infants' heart rate and blood oxygen saturation during and after venipuncture.

Research on an anti-motion interference algorithm of blood oxygen saturation based on AC and DC analysis

BACKGROUND

There is an urgent need for blood oxygen saturation (SpO2) tests when participants are ambulatory, as in daily activity monitoring, sleep monitoring, or even athletes' cardiovascular function tests. In such situations, measuring equipment needs to be wearable. This restricts the processor volume, and the corresponding algorithm should be microprocessor compatible.

OBJECTIVE

This article proposes an anti-motion interference blood oxygen saturation algorithm for the microcontroller based on AC and DC analysis, named de-trended FFT.

METHODS

An experiment was conducted to compare the de-trended FFT algorithm with two other algorithms commonly used in the time and frequency domains. In the experiment, participants' oxygen saturation levels were calculated from Photoplethysmography (PPG) signals that were recorded continuously. Meantime, five types of hand motions were conducted, including hand trembling movements, horizontal hand movements, vertical hand movements, finger tapping, and finger bending, with each state lasting 2 minutes.

RESULTS

Results show significant performance of de-trended FFT in SpO2 calculation (P < 0.05), in both accuracy and stability.

CONCLUSION

De-trended FFT stands out in both mean deviation and variance by eliminating trending influence when compared with the other two algorithms. The motion interference's influence on SpO2 calculation mainly comes from the AC component, not the DC.

Correction and optimization of a T2-based approach to map blood oxygenation in small cerebral veins

PURPOSE

Cerebral venous blood oxygenation (Yv ) is an important biomarker in brain physiology and function. The present study proposes a procedure to provide a quantitative map of the brain's intravascular Yv.

THEORY AND METHODS

The method is based on a pulse sequence, T2 -Relaxation-Under-Phase-Contrast (TRU-PC) MRI, with postprocessing approaches to correct eddy-current effects. A complete scan protocol consists of four TRU-PC scans sensitized to large and small vessels with anterior-posterior and foot-head flow-encoding directions, and the data are analyzed conjunctively. Eddy-current correction was performed by fitting the tissue phase to a hyperplane, and then subtracting the eddy-current phase from the measured vessel phase. The reproducibility of the Yv-maps was examined in five participants. Sensitivity of the Yv map to a caffeine challenge was studied in another five participants.

RESULTS

Removal of eddy-current induced artifact allowed for the correction of T2 measurements, as demonstrated in vivo and with simulation. A Yv-map depicting all vessels in the slice can be obtained with the proposed protocol. Test-retest variability of the Yv -map was 3.7 ± 1.2%. Yv reduction can be reliably detected (P < 0.001) following the caffeine ingestion.

CONCLUSION

With the proposed TRU-PC protocol and eddy-current correction procedure, an accurate, vessel-specific Yv map of the human brain can be obtained.

Dependence of blood T(2) on oxygenation at 7 T: in vitro calibration and in vivo application

PURPOSE

The calibratable relationship between blood oxygenation (Y) and T(2) allows quantification of cerebral venous oxygenation. We aim to establish a calibration plot between blood T(2) , Y, and hematocrit at 7 T, and using T(2) -relaxation-under-spin-tagging MRI, determine human venous blood oxygenation in vivo.

METHODS

In vitro experiments were performed at 7 T on bovine blood samples using a Carr-Purcell-Meiboom-Gill-T2 sequence, from which we characterized the relationship among T(2) , Y, and hematocrit. T(2) -relaxation-under-spin-tagging MRI was implemented at 7 T to measure venous blood T2 in vivo, from which oxygenation was estimated using the in vitro calibration plot. Hyperoxia was performed to test the sensitivity of the method to oxygenation changes, and the 7 T results were compared with those at 3 T.

RESULTS

In vitro data showed that arterial and venous T(2) at 7 T are 68 and 20 ms, respectively, at a typical hematocrit of 0.42. In vivo measurement showed a cerebral venous oxygenation of 64.7 ± 5.0% and a test-retest coefficient-of-variation of 3.6 ± 2.4%. Hyperoxia increased Yv by 9.0 ± 1.4% (P = 0.001) and the 3 and 7 T results showed a strong correlation (R = 0.95) across individuals.

CONCLUSION

We provided an in vitro calibration plot for conversion of blood T(2) to oxygenation at 7 T and demonstrated its utility in vivo.

Quantitative CMR markers of impaired vascular reactivity associated with age and peripheral artery disease

BACKGROUND

The aim of this study was to develop and evaluate an integrated CMR method incorporating dynamic oximetry, blood flow and pulse-wave velocimetry to assess vascular reactivity in patients with peripheral artery disease (PAD) and healthy controls.

METHODS AND RESULTS

The study population consisted of young healthy subjects (YH, 30 ± 7 yrs, N = 19),PAD (71 ± 9 yrs, N = 38), and older healthy controls (OHC, 68 ± 9 yrs, N = 43). Peripheral vascular reactivity was evaluated with two methods, time-resolved quantification of blood flow velocity and oxygenation level in the femoral artery and vein, respectively, performed simultaneously both at rest and hyperemia. Aortic stiffness was assessed via pulse-wave velocity. Oximetric data showed that compared to OHC, the time-course of the hemoglobin oxygen saturation in PAD patients had longer washout time (28.6 ± 1.2 vs 16.9 ± 1.1 s, p < 0.0001), reduced upslope (0.60 ± 0.1 vs 1.3 ± 0.08 HbO2/sec, p < 0.0001) and lower overshoot (8 ± 1.4 vs 14 ± 1.2 HbO2, p = 0.0064). PAD patients also had longer-lasting antegrade femoral artery flow during hyperemia (51 ± 2.1 vs 24 ± 1.8 s, p < 0.0001), and reduced peak-to-baseline flow rate (3.1 ± 0.5 vs 7.4 ± 0.4, p < 0.0001). Further, the pulsatility at rest was reduced (0.75 ± 0.32 vs 5.2 ± 0.3, p < 0.0001), and aortic PWV was elevated (10.2 ± 0.4 vs 8.1 ± 0.4 m/s, p = 0.0048).

CONCLUSION

The proposed CMR protocol quantifies multiple aspects of vascular reactivity and represents an initial step toward development of a potential tool for evaluating interventions, extrapolating clinical outcomes and predicting functional endpoints based on quantitative parameters.

Effects of oxygen concentration and flow rate on cognitive ability and physiological responses in the elderly

The supply of highly concentrated oxygen positively affects cognitive processing in normal young adults. However, there have been few reports on changes in cognitive ability in elderly subjects following highly concentrated oxygen administration. This study investigated changes in cognitive ability, blood oxygen saturation (%), and heart rate (beats/min) in normal elderly subjects at three different levels of oxygen [21% (1 L/min), 93% (1 L/min), and 93% (5 L/min)] administered during a 1-back task. Eight elderly male (75.3 ± 4.3 years old) and 10 female (71.1 ± 3.9 years old) subjects, who were normal in cognitive ability as shown by a score of more than 24 points in the Mini-Mental State Examination-Korea, participated in the experiment. The experiment consisted of an adaptation phase after the start of oxygen administration (3 minutes), a control phase to obtain stable baseline measurements of heart rate and blood oxygen saturation before the task (2 minutes), and a task phase during which the 1-back task was performed (2 minutes). Three levels of oxygen were administered throughout the three phases (7 minutes). Blood oxygen saturation and heart rate were measured during each phase. Our results show that blood oxygen saturation increased, heart rate decreased, and response time in the 1-back task decreased as the concentration and amount of administered oxygen increased. This shows that administration of sufficient oxygen for optimal cognitive functioning increases blood oxygen saturation and decreases heart rate.

Effects of hypoxia on muscle protein synthesis and anabolic signaling at rest and in response to acute resistance exercise

Chronic reductions in tissue O(2) tension (hypoxia) are associated with muscle atrophy and blunted hypertrophic responses to resistance exercise (RE) training. However, the effect of hypoxia on muscle protein synthesis (MPS) at rest and after RE is unknown. In a crossover study, seven healthy men (21.4 ± 0.7 yr) performed unilateral leg RE (6 × 8 repetitions at 70% 1-repetition maximum) under normoxic (20.9% inspired O(2)) and normobaric hypoxic (12% inspired O(2) for 3.5 h) postabsorptive conditions. Immediately after RE the rested leg was biopsied, and a primed continuous infusion of [1,2-(13)C(2)]leucine was maintained for 2.5 h before final biopsies from both legs to measure tracer incorporation and signaling responses (i.e., ribosomal S6 kinase 1). After 3.5 h of hypoxia, MPS was not different from normoxia in the rested leg (normoxia 0.033 ± 0.016 vs. hypoxia 0.043 ± 0.016%/h). MPS increased significantly from baseline 2.5 h after RE in normoxia (0.033 ± 0.016 vs. 0.104 ± 0.038%/h) but not hypoxia (0.043 ± 0.016 vs. 0.060 ± 0.063%/h). A significant linear relationship existed between MPS 2.5 h after RE in hypoxia and mean arterial blood O(2) saturation during hypoxia (r(2) = 0.49, P = 0.04). Phosphorylation of p70S6K(Thr389) remained unchanged in hypoxia at rest but increased after RE in both normoxia and hypoxia (2.6 ± 1.2-fold and 3.4 ± 1.1-fold, respectively). Concentrations of the hypoxia-responsive mTOR inhibitor regulated in development and DNA damage-1 were unaltered by hypoxia or RE. We conclude that normobaric hypoxia does not reduce MPS over 3.5 h at rest but blunts the increased MPS response to acute RE to a degree dependent on extant SpO(2).

Calibration-free absolute quantification of optical absorption coefficients using acoustic spectra in 3D photoacoustic microscopy of biological tissue

Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of nonfluorescent molecules. We propose a method to use acoustic spectra of photoacoustic signals to quantify the absolute optical absorption. This method is self-calibrating and thus insensitive to variations in the optical fluence. Factors such as system bandwidth and acoustic attenuation can affect the quantification but can be canceled by dividing the acoustic spectra measured at two optical wavelengths. Using optical-resolution photoacoustic microscopy, we quantified the absolute optical absorption of black ink samples with various concentrations. We also quantified both the concentration and oxygen saturation of hemoglobin in a live mouse in absolute units.

Minocycline suppresses morphine-induced respiratory depression, suppresses morphine-induced reward, and enhances systemic morphine-induced analgesia

Recent data suggest that opioids can activate immune-like cells of the central nervous system (glia). This opioid-induced glial activation is associated with decreased analgesia, owing to the release of proinflammatory mediators. Here, we examine in rats whether the putative microglial inhibitor, minocycline, may affect morphine-induced respiratory depression and/or morphine-induced reward (conditioned place preference). Systemic co-administration of minocycline significantly attenuated morphine-induced reductions in tidal volume, minute volume, inspiratory force, and expiratory force, but did not affect morphine-induced reductions in respiratory rate. Minocycline attenuation of respiratory depression was also paralleled with significant attenuation by minocycline of morphine-induced reductions in blood oxygen saturation. Minocycline also attenuated morphine conditioned place preference. Minocycline did not simply reduce all actions of morphine, as morphine analgesia was significantly potentiated by minocycline co-administration. Lastly, morphine dose-dependently increased cyclooxygenase-1 gene expression in a rat microglial cell line, an effect that was dose-dependently blocked by minocycline. Together, these data support that morphine can directly activate microglia in a minocycline-suppressible manner and suggest a pivotal role for minocycline-sensitive processes in the mechanisms of morphine-induced respiration depression, reward, and pain modulation.