Changes In Tissue Oxygenation Research Articles

Spatial-Temporal Oxygenation Mapping Using a Near-Infrared Optical Scanner: Towards Peripheral Vascular Imaging.

Near-infrared spectroscopy (NIRS)-based peripheral perfusion, or microcirculation, can be used to assess the severity of peripheral vascular dysfunction. A low-cost, portable non-contact near-infrared optical scanner (NIROS) was developed for spatio-temporal mapping of tissue oxygenation and perfusion in tissues. In vivo validation studies were carried out on control subjects (n = 3) to assess the ability of NIROS to measure real-time oxygenation changes in response to an occlusion paradigm on the dorsum of the hand. NIROS captured real-time tissue oxygenation changes with 95% correlation when compared to a commercial device. A feasibility peripheral imaging study was performed in a mouse model (n = 5) of chronic kidney disease (CKD) induced vascular calcification to assess differences in microcirculatory peripheral tissue oxygenation. The tissue oxygenation (in terms of oxy-, deoxy-, and total hemoglobin changes) due to the occlusion paradigm was distinctly different prior to (week-6) and after the onset of vascular calcification (week-12) in the murine tails. Future work will involve extensive studies to correlate these microcirculatory tissue oxygenation changes in the peripheral tail to the vascular calcification in the heart.

Local microvascular tissue oxygenation of the intrinsic foot muscles in patients with diabetes: A cross-sectional case-comparison study

BackgroundFoot-related complications including impaired peripheral circulation and lower limb ulceration are severe consequences for those with diabetes mellitus. This study aimed to assess differences in tissue oxygenation and oxygen utilization of the plantar surface intrinsic foot muscles between diabetic participants and healthy comparisons following short foot exercise and a standard walking protocol. MethodsEighteen participants, 9 with diabetes and 9 healthy age- and sex-matched comparisons, completed two interventions in a randomized order. For the short foot exercise intervention, participants completed 5 sets of 15 intrinsic foot muscle contractions. For the walking intervention, participants completed a modified six-minute walk test. Tissue oxygenation variables including oxygenated hemoglobin, deoxygenated hemoglobin, and tissue saturation index were measured using near-infrared spectroscopy in quiet stance and during intrinsic foot muscle contraction cycles following each intervention. Means, standard deviations, 95 % confidence intervals, mean differences, and Cohen’s d effect sizes were calculated for each tissue oxygenation variable. ResultsThe results of this study indicated no significant group differences in quiet standing tissue oxygenation measures at baseline and following each intervention. Participants in the diabetic group had significantly less change in tissue saturation index during intrinsic foot muscle contractions compared to healthy participants after the short foot exercise intervention (ES= 4.00, P = .0002) and walking intervention (ES= 1.33, P = .015). ConclusionsBy utilizing wireless NIRS and novel research methodology, this study was able to explore changes in plantar surface tissue oxygenation of the intrinsic foot muscles following a targeted short foot exercise intervention as well as a standard walking protocol in patients diagnosed with diabetes compared to age- and sex- matched individuals without diabetes. We identified that diabetic participants presented with less oxygen utilization during intrinsic foot muscle contractions performed following both exercise interventions compared to their healthy age- and sex- matched comparisons.

Dilation of the superior sagittal sinus detected in rat model of mild traumatic brain injury using 1 T magnetic resonance imaging.

Mild traumatic brain injury (mTBI) is a common injury that can lead to temporary and, in some cases, life-long disability. Magnetic resonance imaging (MRI) is widely used to diagnose and study brain injuries and diseases, yet mTBI remains notoriously difficult to detect in structural MRI. mTBI is thought to be caused by microstructural or physiological changes in the function of the brain that cannot be adequately captured in structural imaging of the gray and white matter. However, structural MRIs may be useful in detecting significant changes in the cerebral vascular system (e.g., the blood-brain barrier (BBB), major blood vessels, and sinuses) and the ventricular system, and these changes may even be detectable in images taken by low magnetic field strength MRI scanners (<1.5T). In this study, we induced a model of mTBI in the anesthetized rat animal model using a commonly used linear acceleration drop-weight technique. Using a 1T MRI scanner, the brain of the rat was imaged, without and with contrast, before and after mTBI on post-injury days 1, 2, 7, and 14 (i.e., P1, P2, P7, and P14). Voxel-based analyses of MRIs showed time-dependent, statistically significant T2-weighted signal hypointensities in the superior sagittal sinus (SSS) and hyperintensities of the gadolinium-enhanced T1-weighted signal in the superior subarachnoid space (SA) and blood vessels near the dorsal third ventricle. These results showed a widening, or vasodilation, of the SSS on P1 and of the SA on P1-2 on the dorsal surface of the cortex near the site of the drop-weight impact. The results also showed vasodilation of vasculature near the dorsal third ventricle and basal forebrain on P1-7. Vasodilation of the SSS and SA near the site of impact could be explained by the direct mechanical injury resulting in local changes in tissue function, oxygenation, inflammation, and blood flow dynamics. Our results agreed with literature and show that the 1T MRI scanner performs at a level comparable to higher field strength scanners for this type of research.

Mouse Cardiac Arrest Model for Brain Imaging and Brain Physiology Monitoring During Ischemia and Resuscitation.

Most cardiac arrest (CA) survivors experience varying degrees of neurologic deficits. To understand the mechanisms that underpin CA-induced brain injury and, subsequently, develop effective treatments, experimental CA research is essential. To this end, a few mouse CA models have been established. In most of these models, the mice are placed in the supine position in order to perform chest compression for cardiopulmonary resuscitation (CPR). However, this resuscitation procedure makes the real-time imaging/monitoring of brain physiology during CA and resuscitation challenging. To obtain such critical knowledge, the present protocol presents a mouse asphyxia CA model that does not require the chest compression CPR step. This model allows for the study of dynamic changes in blood flow, vascular structure, electrical potentials, and brain tissue oxygen from the pre-CA baseline to early post-CA reperfusion. Importantly, this model applies to aged mice. Thus, this mouse CA model is expected to be a critical tool for deciphering the impact of CA on brain physiology.

Measurements of cerebral microvascular blood flow, oxygenation, and morphology in a mouse model of whole-brain irradiation-induced cognitive impairment by two-photon microscopy and optical coherence tomography: evidence for microvascular injury in the cerebral white matter.

Whole-brain irradiation (WBI, also known as whole-brain radiation therapy) is a mainstay treatment modality for patients with multiple brain metastases. It is also used as a prophylactic treatment for microscopic tumors that cannot be detected by magnetic resonance imaging. WBI induces a progressive cognitive decline in ~ 50% of the patients surviving over 6months, significantly compromising the quality of life. There is increasing preclinical evidence that radiation-induced injury to the cerebral microvasculature and accelerated neurovascular senescence plays a central role in this side effect of WBI. To better understand this side effect, male C57BL/6 mice were first subjected to a clinically relevant protocol of fractionated WBI (5Gy, two doses per week, for 4weeks). Nine months post the WBI treatment, we applied two-photon microscopy and Doppler optical coherence tomography to measure capillary red-blood-cell (RBC) flux, capillary morphology, and microvascular oxygen partial pressure (PO2) in the cerebral somatosensory cortex in the awake, head-restrained, WPI-treated mice and their age-matched controls, through a cover-glass-sealed chronic cranial window. Thanks to the extended penetration depth with the fluorophore - Alexa680, measurements of capillary blood flow properties (e.g., RBC flux, speed, and linear density) in the cerebral subcortical white matter were enabled. We found that the WBI-treated mice exhibited a significantly decreased capillary RBC flux in the white matter. WBI also caused a significant reduction in capillary diameter, as well as a large (although insignificant) reduction in segment density at the deeper cortical layers (e.g., 600-700μm), while the other morphological properties (e.g., segment length and tortuosity) were not obviously affected. In addition, we found that PO2 measured in the arterioles and venules, as well as the calculated oxygen saturation and oxygen extraction fraction, were not obviously affected by WBI. Lastly, WBI was associated with a significant increase in the erythrocyte-associated transients of PO2, while the changes of other cerebral capillary PO2 properties (e.g., capillary mean-PO2, RBC-PO2, and InterRBC-PO2) were not significant. Collectively, our findings support the notion that WBI results in persistent cerebral white matter microvascular impairment, which likely contributes to the WBI-induced brain injury and cognitive decline. Further studies are warranted to assess the WBI-induced changes in brain tissue oxygenation and malfunction of the white matter microvasculature as well.

Cardiac and cerebral hemodynamics with umbilical cord milking compared with early cord clamping: A randomized cluster crossover trial

ObjectiveA large, randomized cluster cross-over trial (N = 1730) comparing intact umbilical cord milking (UCM) to early cord clamping (ECC) in non-vigorous near-term/term newborns demonstrated a reduction in cardiorespiratory interventions at birth and less moderate to severe hypoxic ischemic encephalopathy. We evaluated changes in cerebral tissue oxygenation (StO2), pulse oximetry (SpO2), pulse rate and fraction of inspired oxygen (FiO2) during the first 10 min of life in a subset of infants enrolled in the parent trial. Study designInfants enrolled in the Milking in Non-Vigorous Infants trial that had StO2 monitoring at birth were included in the sub-study conducted at 3 hospitals the US and Canada. A near-infrared spectroscopy sensor, pulse oximeter and electrocardiogram electrodes were placed. Pulse rate, StO2, SpO2, and FiO2 were collected for the first 10 min after birth. Longitudinal models were used to compare effects of UCM and ECC. ResultsThirty-four infants had StO2 data. Fifteen of these infants received UCM and 19 had ECC. Infants receiving UCM had similar heart rates, SpO2, and StO2 values, but were exposed to less FiO2 over the first 10 min of life than infants with ECC (0.26 ± 0.12 vs. 0.81 ± 0.05 at 10 min). ConclusionNon-vigorous term/near term infants who received UCM at birth required lower FiO2 after delivery when compared to infants who umbilical cords were clamped soon after birth while achieving similar peripheral and cerebral oxygenation. Cord milking may be a potential option for placental transfusion in non-vigorous near term/term infants when delayed cord clamping cannot be performed.

Cerebral tissue oxygenation response to brain irradiation measured during clinical radiotherapy.

Cancer therapy treatments produce extensive changes in the physiological and morphological properties of tissues, which are also individual dependent. Currently, a key challenge involves developing more tailored cancer therapy, and consequently, individual biological response measurement during therapy, such as tumor hypoxia, is of high interest. This is the first time human cerebral haemodynamics and cerebral tissue oxygenation index (TOI) changes were measured during the irradiation in clinical radiotherapy and functional near-infrared spectroscopy (fNIRS) technique was demonstrated as a feasible technique for clinical use in radiotherapy, based on 34 online patient measurements. Our aim is to develop predictive biomarkers and noninvasive real-time methods to establish the effect of radiotherapy during treatment as well as to optimize radiotherapy dose planning for individual patients. In particular, fNIRS-based technique could offer an effective and clinically feasible online technique for continuous monitoring of brain tissue hypoxia and responses to chemo- and radiotherapy, which involves modulating tumor oxygenation to increase or decrease tumor hypoxia. We aim to show that fNIRS is feasible for repeatability measuring in patient radiotherapy, the temporal alterations of tissue oxygenation induced by radiation. Fiber optics setup using multiwavelength fNIRS was built and combined with a medical linear accelerator to measure cerebral tissue oxygenation changes during the whole-brain radiotherapy treatment, where the radiation dose is given in whole brain area only preventing dosage to eyes. Correlation of temporal alterations in cerebral haemodynamics and TOI response to brain irradiation was quantified. Online fNIRS patient measurement of cerebral haemodynamics during clinical brain radiotherapy is feasible in clinical environment, and results based on 34 patient measurements show strong temporal alterations in cerebral haemodynamics and decrease in TOI during brain irradiation and confirmed the repeatability. Our proof-of-concept study shows evidently that irradiation causes characteristic immediate changes in brain tissue oxygenation. In particular, TOI seems to be a sensitive parameter to observe the tissue effects of radiotherapy. Monitoring the real-time interactions between the subjected radiation dose and corresponding haemodynamic effects may provide important tool for the researchers and clinicians in the field of radiotherapy. Eventually, presented fNIRS technique could be used for improving dose planning and safety control for individual patients.

Observation of Tissue Oxygenation Changes Using Remote Photoplesysmography with a Smartphone.

Tissue oxygenation is a critical marker of tissue status and can be used to evaluate and track wound progress, the viability of transplanted tissue, and burns. Thus, the determination of tissue oxygenation (preferably remotely) is of great importance. Explore the impact of oxygenation changes on tissue color. The rPPG of both hands was acquired using a stand-mounted smartphone (iPhone 8) placed about 10 cm above the hands. A 60s baseline was followed by occlusion of one arm using a cuff inflated to 200mmHg for approximately 2 min. The cuff was then rapidly deflated, followed by a 60s recovery period. The reference muscle oxygenation signal (SmO2) was acquired using the near-infrared contact Moxy device (Fortiori Design LLC) placed on the forearm distal to the occlusion. The data were collected on both hands of 28 healthy volunteers. rPPG can observe changes in tissue oxygenation, which was confirmed across 28 participants using a robust reference standard. We have an initial confirmation of the notion that rPPG can monitor changes in tissue oxygenation. However, a spectrum of rPPG and SmO2 reductions is observed, which should be explored in future work.

Near infrared spectroscopy in monitoring of head and neck microvascular free flaps.

Microvascular free‑flap monitoring is crucial to the early detection of flap failure and increases the chance of early intervention in case of disruption of perfusion to a flap. Many clinical alternatives to classical clinical flap monitoring have been proposed, such as color duplex ultrasonography, handheld Doppler, flap thermometry, or implantable Doppler flowmetry. Early detection of critical changes in tissue oxygenation can lead to successful surgical intervention when problems with flap nutrition arise. Our clinical study seeks to investigate dynamic monitoring of free flaps with near‑infrared spectroscopy (NIRS). NIRS is a non-invasive instrumental technique used for continuous monitoring of peripheral tissue oxygenation (StO2) and microcirculation. All patients were included prospectively from one clinical center. During the clinical research period, 18 patients underwent extraoral head and neck reconstruction with one of three types of free flap, namely with radial forearm free flap (RFFF), anterolateral thigh flap (ALT) or fibula free flap (FFF). Measurements of flap perfusion were taken using NIRS during intraoperative and postoperative phases for 71 hours on average. A total of 6 perfusion disorders were recorded, of which three originated from microanastomoses and three from postoperative bleeding and compression of pedicle. NIRS showed characteristic changes in all 6 cases that were returned to the operating theatre owing to pedicle compromise. In these cases, NIRS had detected the pedicle compromise before it was clinically identified. A single StO2 monitoring was able to detect the vascular compromise with 100% sensitivity and 95.65% specificity. None of the cases were falsely positive. In our study, all compromised flaps were accurately identified by means of NIRS. In most cases, the changes in oxygen saturation became evident on NIRS prior to being clinically observed. In our study, the continuous NIRS monitoring securely detected the early stages of arterial and venous thromboses or pedicle compression. The most important aspects of monitoring the flaps´ microvascular perfusion and vitality by means of NIRS lie in its function of recording the dynamics of changes in the values ​​of absolute oxygen saturation (StO2> 50%) alongside with detecting a 30% decrease in tissue saturation over a 60‑minute interval (60 min StO2 >30%) before the clinical changes in the microvascular flap become observable. In cases of pedicle compression, the average time of appearance of signs of StO2 values dropping below the reference interval (as detected by NIRS) was 1:29:02 hour (SD= 0:58:42 h) prior to the occurrence of any clinical signs, while in cases of microvascular anastomosis complications, it was 0:35:23 hour (SD=0:08:30 h) (SD = 0:08:30 h) (Tab. 3, Fig. 7, Ref. 42).

Evaluating renal microcirculation in patients with acute kidney injury by contrast-enhanced ultrasonography: a protocol for an observational cohort study.

Acute kidney injury (AKI) in critically ill patients has poor renal outcome with high mortality. Changes in intra-renal microcirculation and tissue oxygenation are currently considered essential pathophysiological mechanisms to the development and progression of AKI. This study aims to investigate the characteristics of contrast-enhanced ultrasonography (CEUS) derived parameters in biopsy-proven AKI patients, and examine the predictive value of these markers for renal outcome. This prospective observational study will enroll AKI patients who are diagnosed and staging following KDIGO (Kidney Disease: Improving Global Outcomes) criteria. All patients undergo a kidney biopsy and pathological tubulointerstitial nephropathy is confirmed. The CEUS examination will be performed at 0, 4 and 12weeks after biopsy to monitor renal microcirculation. The percentage decrease of serum creatinine, 4-week and 12-week eGFR (estimated glomerular filtration rate) will also be reviewed as renal prognosis. The relationship of CEUS parameters with clinical and pathological markers will be analyzed. We perform a lassologit procedure to select potential affecting variables, including clinical, laboratory indexes and CEUS markers, to be included in the logistic regression model, and examine their predictive performance to AKI outcomes. If we are able to show that CEUS derived parameters contribute to diagnosis and prognosis of AKI, the quality of life of patients will be improved while healthcare costs will be reduced. This study is retrospectively registered on the Chinese Medical Research Registration information System( https://61.49.19.26/login ) on December 31, 2021: MR-11-22-003,503. This study has been approved by the Ethics and Scientific Research Department of Peking University First Hospital.

Cerebral oximetry using near-infrared spectroscopy (NIRS) in cardiovascular and thoracic anaesthesia: A review

Near-infrared Spectroscopy (NIRS) has a well-established role in cardiovascular and thoracic anaesthesia, and its use is increasing in popularity. Regional cerebral oxygen saturation monitoring may be helpful for patients who are at risk for cerebral ischemia. During cardiac induction, there is a risk of developing complications like arrhythmias, hypotension, cardiac arrest, ST-segment changes, acute low cardiac output, pulmonary hypertension, diastolic dysfunction, valve dysfunction, residual shunts, or residual obstruction of ventricular outflow tracts, brain injuries, etc; where cerebral oxygen saturation is affected. These complications are multifactorial due to the use of heartlung machines as a result of the issues of aorto-pulmonary shunts, pathophysiological changes in the cardiovascular system, hypothermia, circulatory arrest (DHA), prolonged CPB time, specific surgical technique, anaesthesia, and different medications. The non-invasive, compact, continuous measurement technology known as NIRS tracks oxygenation in the brain, muscle, and other organs. In real time, it senses small changes in tissue oxygenation. We hypothesized that NIRS would be a useful technique for detecting increased susceptibility to ischemic neurologic harm. It could be a helpful technique for tracking brain oxygenation when jugular bulb oxygen saturation monitoring is not an option. NIRS is a useful tool for predicting critical events and figuring out how to handle them for a better outcome and faster discharge.

Peripheral muscle oxygenation and symptoms of stress in adolescents with and without temporomandibular disorder.

To compare peripheral muscle oxygenation levels and the prevalence of psychological stress in adolescents with and without temporomandibular disorder (TMD). A cross-sectional study was performed with adolescents submitted into two groups: those diagnosed with TMD (DG) and control (CG). Muscle oxygenation was measured by near-infrared spectroscopy in the masseter and upper trapezius muscles. Symptoms of stress were assessed by Lipp's Stress Symptom Inventory for Adults or Child Stress Scale. A Student t-test was used for intergroup comparisons and association between categorical variables by chi-square test, phi coefficient of correlation, odds ratio, and two-way ANOVA. Fifty-three adolescents were evaluated and a significant reduction was observed in the oxyhemoglobin level in the masseter muscle at rest (p = 0.04) and contraction (p = 0.02). A greater total hemoglobin level was found in the upper trapezius muscle at rest in DG (p = 0.03), with a significant difference in the tissue saturation index during contraction (p = 0.05) intergroup. Individuals in the DG were 4.523 times more likely to exhibit signs and symptoms of stress than in CG. Adolescents from DG showed reduced masseter oxyhemoglobin values at rest and during contraction and showed more signs and symptoms of stress than healthy controls. In the upper trapezius, DG showed higher values of total circulating hemoglobin, essential for greater blood flow and efficient maximum voluntary contraction. Changes in tissue oxygenation and stress in adolescents with TMD prompted the earlier treatment of this population to prevent disease progression into adulthood.

Splanchnic-cerebral oxygenation ratio associated with packed red blood cell transfusion in preterm infants.

Splanchnic-cerebral oxygenation ratio (SCOR), the ratio of splanchnic tissue oxygen (StO2 s) to simultaneously measured cerebral tissue oxygen (StO2 c), has been described as a surrogate to detect impaired splanchnic oxygenation associated with hypoperfusion status such as necrotizing enterocolitis. This concept is based on the presumption that any change in SCOR indicates a corresponding change in splanchnic tissue oxygenation as the numerator, whereas cerebral tissue oxygenation as the denominator remains stable. However, it is questionable to utilise this concept to detect splanchnic oxygenation changes in the context of packed red blood cell transfusion (PRBCT). The current study examines the contribution of both cerebral and splanchnic oxygenation components to PRBCT-associated SCOR changes in preterm infants. Prospective cohort study. Neonatal intensive care. Hemodynamically stable infants: Gestation <32 weeks; birth weight <1500 g; postmenstrual age <37 weeks: tolerating ≥120 ml/kg/day feed volume. PRBCT at 15 ml/kg, over 4 h. Transfusion-associated changes were determined by performing mixed models for repeated measures analysis between the 4-h mean pre-transfusion values (SCOR 0, StO2 s 0, and StO2 c 0) and the post-transfusion hourly mean values for the next 28 h (SCOR 1-28, StO2 s 1-28, and StO2 c 1-28). Dunnett's method was used to adjust for the multiplicity of the p value. Of 30 enrolled infants 14 [46.7%] male; median [IQR] birth weight, 923 [655-1064] g; gestation, 26.4 [25.5-28.1] weeks; enrolment weight, 1549 [1113-1882] g; and postmenstrual age, 33.6 [32.4-35.0] weeks, one infant was excluded because of corrupted NIRS data. With the commencement of PRBCT, SCOR demonstrated a downward trend throughout the study period. This drift was associated with an increasing StO2 c trend, while StO2 s remained unchanged throughout the study period. PRBCT-associated SCOR decrease suggests improvement in cerebral oxygenation rather than worsening splanchnic oxygenation. Our study underlines that it is necessary to determine individual components of SCOR, namely cerebral and splanchnic StO2 to understand SCOR changes in the context of PRBCT.

Cocaine’s cerebrovascular vasoconstriction is associated with astrocytic Ca2+ increase in mice

Human and animal studies have reported widespread reductions in cerebral blood flow associated with chronic cocaine exposures. However, the molecular and cellular mechanisms underlying cerebral blood flow reductions are not well understood. Here, by combining a multimodal imaging platform with a genetically encoded calcium indicator, we simultaneously measured the effects of acute cocaine on neuronal and astrocytic activity, tissue oxygenation, hemodynamics and vascular diameter changes in the mouse cerebral cortex. Our results showed that cocaine constricted blood vessels (measured by vessel diameter Φ changes), decreasing cerebral total blood volume (HbT) and temporally reducing tissue oxygenation. Cellular imaging showed that the mean astrocytic Ca2+ dependent fluorescence (Delta {F/F}_{{{{rm{Ca}}}^{2+}}{mbox{-}{{{rm{G(A)}}}}}}) increase in response to cocaine was weaker but longer lasting than the mean neuronal Ca2+ dependent fluorescence (Delta {F/F}_{{{{rm{Ca}}}^{2+}}{mbox{-}{{{rm{G(N)}}}}}}) changes. Interestingly, while cocaine-induced Delta {F/F}_{{{{rm{Ca}}}^{2+}}{mbox{-}{{{rm{G(N)}}}}}} increase was temporally correlated with tissue oxygenation change, the Delta {F/F}_{{{{rm{Ca}}}^{2+}}{mbox{-}{{{rm{G(A)}}}}}} elevation after cocaine was in temporal correspondence with the long-lasting decrease in arterial blood volumes. To determine whether the temporal association between astrocytic activation and cocaine induced vasoconstriction reflected a causal association we inhibited astrocytic Ca2+ using GFAP-DREADD(Gi). Inhibition of astrocytes attenuated the vasoconstriction resulting from cocaine, providing evidence that astrocytes play a critical role in cocaine’s vasoconstrictive effects in the brain. These results indicate that neurons and astrocytes play different roles in mediating neurovascular coupling in response to cocaine. Our findings implicate neuronal activation as the main driver of the short-lasting reduction in tissue oxygenation and astrocyte long-lasting activation as the driver of the persistent vasoconstriction with cocaine. Understanding the cellular and vascular interaction induced by cocaine will be helpful for future putative treatments to reduce cerebrovascular pathology from cocaine use.

Measurement of Revascularization Effect Using Near Infrared Spectroscopy in Below the Knee Arteries.

Current methods evaluating tissue ischemia are based mainly on evaluating blood flow and not tissue perfusion. However, diabetes mainly affects small vessels and blood flow evaluation is insufficient. The aim of the trial was to evaluate the feasibility of NIRS in measuring perfusion changes during chronic total occlusion (CTO) revascularization in below the knee (BTK) arteries. A prospective observational study was performed. During the endovascular revascularization procedure, tissue oxygenation changes were measured using three NIRS sensors. Postoperative angiographies and 30 days wound healing was evaluated. The study enrolled 30 patients with chronic limb threatening ischemia, occluded below the knee arteries, Rutherford 5. Mean age 74.7 11.2 years, 16 (53%) of the patients had diabetes mellitus, 10 (33%) had end-stage renal disease. A statistically significant NIRS increase was observed on sensors near the wound after the revascularization, p = 0.001. Thirty days follow-up visits included 27 patients, because 3 patients had died. Comparing good wound healing group with poor wound healing group intraoperative NIRS increase difference was statistically significant, p = 0.017. The study confirmed tissue perfusion increase could be detected using NIRS during revascularization of below the knee arteries. An intraoperative increase of NIRS proved to predict wound healing results.

Cognitive Function Mainly Shaped by Socioeconomic Status Rather Than Chronic Hypoxia in Adolescents at High Altitude.

Yu, Linyang, Jinqing Feng, Chen Zhou, Xiaohan Zhu, Xiaobin Lou, Jian Yang, Haiying Qi, and Jia Li. Cognitive function mainly shaped by socioeconomic status rather than chronic hypoxia in adolescents at high altitude. High Alt Med Biol. 23:223-231, 2022. Background: The study evaluated cognitive function in relation to the changes in brain tissue oxygenation in three groups of high school students from different socioeconomic regions including Tibetans in Jiuzhi and Lhasa (both at 3,600 m), and Han in Beijing (44 m). Methods: Jiuzhi, Lhasa, and Beijing Group included 21 Tibetans, 24 Tibetans, and 23 Han, respectively. Wechsler Intelligence Scale was used for cognitive evaluation. Functional near infrared spectroscopy was used to measure the changes of oxygenated hemoglobin (oxy-Hb) during the cognitive assessment. Gross domestic product (GDP) was used to indicate the socioeconomic status. Results: All the cognitive scores were significantly lower in the two high altitude groups compared with the Beijing Group (p < 0.001). The scores in Jiuzhi Group were significantly lower compared with the Lhasa Group (p < 0.001). The changes in oxy-Hb in channels 6 and 15 in both high-altitude groups were significantly greater compared with the Beijing Group (p < 0.05), without significant difference between the two high-altitude groups. GDP was significantly correlated with all the scores (p < 0.001), but not altitude. Conclusions: Cognitive impairment occurs in adolescents at high altitude, being severer in Jiuzhi Group compared with the Lhasa Group. The lower performance in both high-altitude groups require greater brain activity over-compensated by cerebral oxygen delivery as indicated by the changes in oxy-Hb. The cognitive scores were significantly correlated with GDP rather than altitude. Cognitive function in adolescents at high altitude is not limited by chronic hypoxia, but mainly shaped by socioeconomic determinants.

Assessment of Tissue Oxygenation and Radiation Dermatitis Pre-, During, and Post-Radiation Therapy in Breast Cancer Patients.

Over 95% of breast cancer patients treated with radiation therapy (RT) undergo an adverse skin reaction known as radiation dermatitis (RD). Assessment of severity or grading of RD is clinically visual and hence subjective. Our objective is to determine sub-clinical tissue oxygenation (oxygen saturation) changes in response to RT in breast cancer patients using near-infrared spectroscopic imaging and correlate these changes to RD grading. A 4-8 week longitudinal pilot imaging study was carried out on 10 RT-treated breast cancer patients. Non-contact near-infrared spectroscopic (NIRS) imaging was performed on the irradiated ipsilateral and the contralateral breast/chest wall, axilla and lower neck regions before RT, across the weeks of RT, and during follow-up after RT ended. Significant changes (p < 0.05) in oxygen saturation (StO2) of irradiated and contralateral breast/chest wall and axilla regions were observed across weeks of RT. The overall drop in StO2 was negatively correlated to RD scaling (in 7 out of 9 cases) and was higher in the irradiated regions when compared to its contralateral region. Differences in the pre-RT StO2 between ipsilateral and contralateral chest wall is a potential predictor of the severity of RD. The subclinical recovery of StO2 to its original state was longer than the visual recovery in RD grading scale, as observed from the post-RT assessment of tissue oxygenation.

Assessment of microcirculatory changes in local tissue oxygenation after revascularization for peripheral arterial disease with the Hyperview®, a portable hyperspectral imaging device.

The Hyperview® is a hyperspectral camera, which can be used to assess the microcirculation of patients with peripheral arterial disease (PAD) and/or diabetes mellitus (DM). It measures local tissue oxygenation in concentrations of oxyhemoblobin (OXY), deoxyhemoglobin (DEOXY), and O2-saturation (O2-SAT) in arbitrary units. The aim of this validation study is to assess whether the Hyperview® is able to monitor microcirculatory changes after revascularization in patients with PAD. In this prospective observational cohort study, 50 patients with PAD were included who were scheduled for endovascular, hybrid, or open revascularization. The ankle-brachial index (ABI), systolic toe pressure (TP) (in case of DM), and a set of Hyperview® measurements of the plantar region were recorded before and after treatment. Changes in pre- and postoperative measurements were assessed with the paired t-test. Some 38 patients underwent endovascular revascularization and eight patients underwent hybrid or open vascular surgical revascularization. After revascularization, the ABI improved from 0.58 to 0.80 (p < 0.001). OXY increased from 72.6 to 77.8 (p = 0.134). DEOXY decreased from 69.1 to 55.0 (p < 0.001). O2-SAT increased from 51.3 to 58.1 (p < 0.001). TP improved from 50.6 to 61.9mmHg (p = 0.065) but was measured in only 16 patients. The Hyperview® is able to observe changes in the microcirculation after revascularization in terms of DEOXY and O2-SAT. The results of this study are a promising step into the validation of the Hyperview®.

Cerebrovascular Function, Vascular Risk, and Lifestyle Patterns in Resistant Hypertension.

Impaired cerebrovascular reactivity (CVR) and blunted cerebral hemodynamic recruitment are thought to be important mechanisms linking hypertension to cerebrovascular and cognitive outcomes. Few studies have examined cardiovascular or dietary correlates of CVR among hypertensives. To delineate associations between cardiometabolic risk, diet, and cerebrovascular functioning among individuals with resistant hypertension from the TRIUMPH trial (n = 140). CVR was assessed by examining changes in tissue oxygenation (tissue oxygenation index [TOI] and oxygenated hemoglobin [HBO2]) using functional near-infrared spectroscopy (fNIRS) during a breath holding test, a standardized CVR assessment to elicit a hypercapnic response. Participants also underwent fNIRS during three cognitive challenge tasks. Vascular function was assessed by measurement of brachial artery flow-mediated dilation and hyperemic flow response. Cardiometabolic fitness was assessed from peak VO2 on an exercise treadmill test and body mass index. Dietary patterns were quantified using the DASH eating score. Cognitive function was assessed using a 45-minute test battery assessing Executive Function, Processing Speed, and Memory. Greater levels fitness (B = 0.30, p = 0.011), DASH compliance (B = 0.19, p = 0.045), and lower obesity (B = -0.30, p = 0.004), associated with greater changes in TOI, whereas greater flow-mediated dilation (B = 0.19, p = 0.031) and lower stroke risk (B = -0.19, p = 0.049) associated with greater HBO2. Similar associations were found for cerebral hemodynamic recruitment, and associations between CVR and cognition were moderated by duration of hypertension. Impaired CVR elevated cardiometabolic risk, obesity, vascular function, and fitness among hypertensives.

Abstract 303: Monitoring Tissue Oxygen Dynamics With A Novel Implantable Hydrogel Sensor In Patients With Pad

Objective: Tissue perfusion measurement remains a fundamental challenge in management of peripheral arterial disease (PAD) patients. Better measurement of baseline and dynamic changes after revascularization would aid clinical judgement. The Wireless Lumee® Oxygen System represents a novel approach to tracking tissue oxygen via a subcutaneous hydrogel that provides noninvasive optical oxygen measurements. This study’s objective was to assess the correlation of the Lumee sensor with transcutaneous oximetry (tcpO2) in PAD patients. Methods: The Lumee® Oxygen System is a subcutaneously placed hydrogel (0.5x0.5x5mm). Optical signals are captured with a skin surface reader sensing extravascular oxygenation. A pilot study assessed in vivo performance with inclusion criteria of peripheral arterial disease (Rutherford I-IV). Sensors were injected in the arm and foot and oxygenation measured before, during, and after proximal blood pressure cuff inflation (Figure) and Buerger’s Test modulation. The correlation (R) of oxygenation between tcpO2 and Lumee® was assessed following sensor placement at 2, 10, 90, 180, and 365 days. Results: Eleven subjects had 148 occlusion modulations over 199 days. Mean age was 67 years (range: 55-88), with 9% females, 45% White and 55% Black Race, Rutherford class I: 36%, II: 36%, III:27%. The median ABI was 0.83 (IQR0.69-1.14). In the arm, modulation was 56.9±24.6% (Lumee) and 84.7±9.2% (tcpO2), R:0.81. In the foot, modulation was 63.4±22.7% (Lumee) and 80.4±15.5% (tcpO2), R:0.79. No injection related adverse events occurred. Conclusion: Occlusion related changes in tissue oxygen can be detected by both tcpO2 and the Lumee sensor which strongly correlate in both the arm and foot. This pilot phase study supports expansion of the trial. The Lumee sensor shows promise for future evaluation of tissue oxygenation in PAD patients, which could be used to assess changes in tissue oxygenation over time and following revascularization.