Tissue Hemoglobin Concentration Research Articles

Non-invasive point-of-care optical technique for continuous invivo assessment of microcirculatory function: Application to a preclinical model of early sepsis.

Increased amplitude of peripheral vasomotion is a potential early marker of sepsis-related microcirculatory impairment; however, previous reports relied on clinically unsuitable invasive techniques. Hyperspectral near-infrared spectroscopy (hsNIRS) and diffuse correlation spectroscopy (DCS) are non-invasive, bedside techniques that can be paired to continuously monitor tissue hemoglobin content (HbT), oxygenation (StO2), and perfusion (rBF) to detect vasomotion as low-frequency microhemodynamic oscillations. While previous studies have primarily focused on the peripheral microcirculation, cerebral injury is also a common occurrence in sepsis and hsNIRS-DCS could be used to assess cerebral microcirculatory function. This work aimed to use a hybrid hsNIRS-DCS system to continuously monitor changes in the peripheral and cerebral microcirculation in a rat model of early sepsis. It was hypothesized that the skeletal muscle would be a more sensitive early indicator of sepsis-related changes in microhemodynamics than the brain. Control animals received saline while the experimental group received fecal slurry to induce sepsis. Subsequently, hsNIRS-DCS measurements were acquired from the skeletal muscle and brain for 6 h. Peripheral rBF rapidly decreased in septic animals, but there were no significant changes in peripheral HbT or StO2, nor cerebral HbT, rBF, or StO2. The power of low-frequency peripheral oscillations in all parameters (i.e., HbT, StO2, and rBF) as well as cerebral HbT oscillations were elevated in septic animals during the final 4 h. These findings suggest that in the early stages of sepsis, while vital organs like the brain are partly protected, changes in peripheral perfusion and vasomotor activity can be detected using hsNIRS-DCS. Future work will apply the technique to ICU patients.

Hyperspectral Imaging for Microcirculatory Assessment of Patients undergoing Transcatheter and Surgical Aortic Valve Replacement-a Prospective Observational Pilot Study.

This prospective, observational study evaluated Hyperspectral Imaging (HSI) to assess the effects of cardiac surgery and cardiopulmonary bypass (CPB) on microcirculation. 40 Patients with severe aortic stenosis were enrolled. 20 patients underwent transapical/transaxillary/transaortic aortic valve replacement (TAVR), 20 underwent an open surgical approach with CPB (SAVR). HSI was used to determine tissue oxygenation (StO2 and NIR), hemoglobin (THI) and water content (TWI) at the palm before/after surgery (T1/T2), and on the third postoperative day (T3). TAVR patients showed no significant changes of microcirculatory parameters during surgery. TWI significantly increased until T3. SAVR patients showed an increase of TWI and a decrease of THI, while StO2 and NIR remained unchanged at T2. In SAVR patients, StO2 and NIR correlated negatively with the duration of CPB and StO2 correlated with intraoperative urine output at T2. HSI was able to detect microcirculatory changes during cardiac surgery. CPB duration seemed to affect tissue oxygenation. Clinical trial registration: (German Clinical Trial Register): DRKS00024765.

Evaluation of inhibitory potential of the flavonoid-rich fraction of Myrica esculenta Buch.-Ham. ex D. Don against DSS-induced colonic inflammation in mice

ObjectiveMyrica esculenta (family Myricaceae), a valuable plant species in China and India, has been traditionally used by many tribes and local communities to manage gut disorders. Scientific validation of its anti-ulcerative colitis activity was aimed. MethodsThe ethyl acetate fraction of Myrica esculenta (MeEa) was prepared and evaluated for its potency against DSS-induced ulcerative colitis (UC) in mice at 200 and 400 mg/kg BW oral dose. The effective dose of MeEa was determined through its effect on DSS-induced UC and was further analyzed through its effects on disease activity index (DAI), colon length, colon weight/length ratio, spleen weight, serum and colon tissue cytokine level, cell count and hemoglobin content. Further, the effect was determined through histopathology and FITC-dextran-induced membrane permeability assay. ResultsBetween the two doses, MeEa at 400 mg/kg BW was found to be the most effective dose in terms of reduced DAI scores, protected colon length from shortening, decreased colon weight/length ratio, reduced spleen weight, decreased pro-inflammatory cytokine level and stabilized the anti-inflammatory cytokine level in serum and colon tissue. MeEa 400 reduced cell counts and increased hemoglobin content and platelet count. MeEa 400 also prevented the colon by protecting epithelial cells and crypts. MeEa 400 provided significant protection from intestinal leakage and reduced FITC dextran level in serum. DiscussionMeEa 400 possesses significant anti-inflammatory potential and acts via attenuation of DSS-induced UC and inhibition of DAI scores. It reduces pro-inflammatory cytokines and stabilizes anti-inflammatory cytokine levels, reduces cell count, and protects epithelial tissue and crypts in the colon, as well as intestinal membrane leakage that occurred due to FITC-dextran administration in mice.

Enhanced peripheral tissue oxygenation and hemoglobin concentration after a high-fat meal measured with spatial frequency domain imaging

Enhanced peripheral tissue oxygenation and hemoglobin concentration after a high-fat meal measured with spatial frequency domain imaging

Effects of volume management on free flap perfusion and metabolism in a large animal model study.

Free flap failure represents a substantial clinical burden. The role of intraoperative volume management remains controversial, with valid studies lacking. Here, using a large animal model, we investigated the influence of volume management on free flap perfusion and metabolism. Autotransfer of a musculocutaneous gracilis flap was performed on 31 German domestic pigs, with arterial anastomosis and catheterization of the pedicle vein for sequential blood sampling. Flap reperfusion was followed by induction of a hemorrhagic shock with maintenance for 30 min and subsequent circulation stabilization with crystalloid solution, crystalloid solution and catecholamine, autotransfusion or colloidal solution. Flap perfusion and oxygenation were periodically assessed using hyperspectral imaging. Flap metabolism was assessed via periodic blood gas analyses. Hyperspectral imaging revealed no difference in either superficial or deep tissue oxygen saturation, tissue hemoglobin or tissue water content between the test groups at any time point. Blood gas analyses showed that lactate levels were significantly increased in the group that received crystalloid solution and catecholamine, after circulatory stabilization and up to 2 h after. We conclude that, in hemorrhagic shock, volume management impacts acid-base balance in free flaps. Crystalloid solutions with norepinephrine increase lactate levels, yet short-term effects on flap perfusion seem minimal, suggesting that vasopressors are not detrimental.

Switchable LED-based laparoscopic multispectral system for rapid high-resolution perfusion imaging.

Multispectral imaging (MSI) is an approach for real-time, quantitative, and non-invasive tissue perfusion measurements. Current laparoscopic systems based on mosaic sensors or filter wheels lack high spatial resolution or acceptable frame rates. To develop a laparoscopic system for MSI-based color video and tissue perfusion imaging during gastrointestinal surgery without compromising spatial or temporal resolution. The system was built with 14 switchable light-emitting diodes in the visible and near-infrared spectral range, a 4K image sensor, and a 10mm laparoscope. Illumination patterns were created for tissue oxygenation and hemoglobin content monitoring. The system was calibrated to a clinically approved laparoscopic hyperspectral system using linear regression models and evaluated in an occlusion study with 36 volunteers. The root mean squared errors between the MSI and reference system were 0.073 for hemoglobin content, 0.039 for oxygenation in deeper tissue layers, and 0.093 for superficial oxygenation. The spatial resolution at a working distance of 45mm was . The effective frame rate was 20fps. High-resolution perfusion monitoring was successfully achieved. Hardware optimizations will increase the frame rate. Parameter optimizations through alternative illumination patterns, regression, or assumed tissue models are planned. Intraoperative measurements must confirm the suitability during surgery.

Cerebral Hemodynamics in Infants with Sickle Cell Disease Indicate Presence of Early Hemodynamic Stress

Introduction: One of the most severe complications of sickle cell disease (SCD) is ischemic brain injury, caused by a combination of decreased oxygen transport delivery related to intravascular vaso-occlusion of sickle erythrocytes and/or cerebral vasculopathy. While newborn screening programs diagnose SCD shortly after birth, routine risk assessment for stroke typically starts with transcranial ultrasound doppler (TCD) at two years of age or later. Yet, little is known about how SCD affects cerebral hemodynamics during infancy, a crucial period for brain development. To address this gap, we used advanced quantitative near-infrared spectroscopy (qNIRS) to non-invasively monitor cerebral tissue hemoglobin concentration (HbT), oxygenation (SO 2), oxygen extraction fraction (cFTOE), blood flow (CBF), and oxygen metabolism (CMRO 2) in infants with SCD. Abnormal CBF and cFTOE indicate hemodynamic stress that may increase stroke risk. Our study aims to investigate the effects of SCD on cerebral oxygen transport in infancy and its associations with age and blood hemoglobin concentration (HgB). Methods: This is a subgroup analysis of a prospective, observational neuroimaging study of SCD at Boston Children's Hospital (NCT 04166526). Inclusion criteria of this subgroup are SCD patients age less than 24 months old at the time of enrollment who are not receiving chronic transfusions. Families read and signed informed consent before participating in research activities. Measurements were conducted with the patients' normally scheduled hematology appointments at Boston Children's Hospital. During each measurement session, bilateral frontal regions of the head were measured up to six times for 30 seconds each. qNIRS variables were compared with literature values obtained with the same optical technologies from a cohort of typically developed infants around 1 year old, equivalent to the median age in this study 1. Correlation analysis was used to analyze qNIRS variables with age and HgB from clinical lab tests. Results: To date, 8 (F/M: 4/4; HbSS/HbS/B +-thalassemia/HbSC: 6/1/1) patients were enrolled with a total of 16 measurements. The meanSD age at measurement was 11.5 5.23 months and the median (IQR) HgB was 9.4 (8.9-10) g/dL. Seven (44%) measurements were performed while patients were receiving treatment with hydroxyurea. There was no difference in HgB in the groups with and without hydroxyurea, though the treatment group was older (mean age: 15.4 vs 8.4 months, P=0.002). Group averages of qNIRS variables are summarized Table 1. Average cFTOE was 0.53 ± 0.07, significantly higher than the reference value of 0.32 (mean difference: 0.21, P<0.001), while the cohort's mean SO 2 of 45.78 ± 7.13% was significantly lower than the reference value of 68% (mean difference: -22.2, P<0.001). Furthermore, cFTOE inversely correlated with HgB (r= -0.63, P=0.04) while SO 2 increased with HgB (r= 0.63, P=0.04). HbT and cerebral blood volume (CBV) were also significantly lower than the reference values (mean difference of -24.8 μM and -0.75 ml/100g, P<0.001 and P<0.02, respectively) and positively correlated with age (r=0.51 and 0.57, P=0.04). CBF did not correlate with either age or HgB. Hemodynamic variables did not differ between groups with and without hydroxyurea, except for HbT and CBV likely secondary to the cohort age difference. Taken together, this suggests that CBF compensatory mechanisms were insufficient to prevent elevated oxygen extraction. Summary: These preliminary results suggest that inadequate oxygen transport to the brain secondary to SCD evokes a compensatory increase in cFTOE starting in early infancy. The progressive hemodynamic stress to brain health during the period of the brain's greatest growth and metabolic demand for oxygen is concerning because of the potential for injury as compensatory mechanisms become exhausted. Hydroxyurea did not reduce this stress, but may have prevented further declines. Recruitment is ongoing to increase the size of the cohort and to continue following patients' trajectories with age. We demonstrated the potential of qNIRS as biomarkers of cerebral hemodynamic compensation to determine when intervention is necessary and evaluate the effectiveness of a chosen intervention in individual patients. 1. Franceschini, M. A. et al. Assessment of infant brain development with frequency-domain near-infrared spectroscopy. Pediatr Res 61, 546-551, 2007.

Increased brain microvascular hemoglobin concentrations in children with cerebral malaria.

Brain swelling is associated with death from cerebral malaria, but it is unclear whether brain swelling is caused by cerebral edema or vascular congestion-two pathological conditions with distinct effects on tissue hemoglobin concentrations. We used near-infrared spectroscopy (NIRS) to noninvasively study cerebral microvascular hemoglobin concentrations in 46 Malawian children with cerebral malaria. Cerebral malaria was defined by the presence of the malaria parasite Plasmodium falciparum on a blood smear, a Blantyre coma score of 2 or less, and retinopathy. Children with uncomplicated malaria (n = 33) and healthy children (n = 29) were enrolled as comparators. Cerebral microvascular hemoglobin concentrations were higher among children with cerebral malaria compared with those with uncomplicated malaria [median (25th, 75th): 145.2 (95.2, 190.0) μM versus 82.9 (65.7, 105.4) μM, P = 0.008]. Cerebral microvascular hemoglobin concentrations correlated with brain swelling score determined by MRI (r = 0.37, P = 0.03). Fluctuations in cerebral microvascular hemoglobin concentrations over a 30-min time period were characterized using detrended fluctuation analysis (DFA). DFA determined self-similarity of the cerebral microvascular hemoglobin concentration signal to be lower among children with cerebral malaria compared with those with uncomplicated malaria [0.63 (0.54, 0.70) versus 0.91 (0.82, 0.94), P < 0.0001]. The lower self-similarity of the hemoglobin concentration signal in children with cerebral malaria suggested impaired regulation of cerebral blood flow. The elevated cerebral tissue hemoglobin concentration and its correlation with brain swelling suggested that excess blood volume, potentially due to vascular congestion, may contribute to brain swelling in cerebral malaria.

Point-of-Care Tissue Oxygenation Assessment with SnapshotNIR for Alloplastic and Autologous Breast Reconstruction.

Patients receiving immediate alloplastic reconstruction after mastectomy or autologous reconstruction were enrolled. Preoperative, intraoperative, and postoperative images were taken of the flaps. StO2 and hemoglobin were measured at the following locations: superior and inferior breast, free flap skin paddle (when applicable), and un-operated control skin. Linear mixed effects model for repeated measurements was used to model measurements to estimate the area effect difference across time, time effect difference across area, and pairwise comparisons between two areas at each time point. Thirty-two breasts underwent alloplastic reconstruction; 38 breasts underwent autologous reconstruction. No enrollees developed skin necrosis. StO2 was highest after mastectomy and closure in alloplastic reconstructions. StO2 was observed to decline at follow-up in autologous reconstructions. Mean preoperative StO2 was highest in breasts that had previously undergone mastectomy and alloplastic reconstruction. The SnapshotNIR device detected normal spatial and temporal differences in tissue oxygenation over the operative course of alloplastic and autologous breast reconstruction. A multi-institutional, prospective clinical trial is needed to determine the sensitivity and specificity of this device for detecting skin flap necrosis.

Tissue Oxygenation Around Capillaries: Effects of Hematocrit and Arteriole Oxygen Condition.

Oxygen transfer in the microvasculature is a complex phenomenon that involves multiple physical and chemical processes and multiple media. Hematocrit, the volume fraction of red blood cells (RBCs) in blood, has direct influences on the blood flow as well as the oxygen supply in the microcirculation. On the one hand, a higher hematocrit means that more RBCs present in capillaries, and thus, more oxygen is available at the source end. On the other hand, the flow resistance increases with hematocrit, and therefore, the RBC motion becomes slower, which in turn reduces the influx of oxygen-rich RBCs entering capillaries. Such double roles of hematocrit have not been investigated adequately. Moreover, the oxygen-hemoglobin dissociation rate depends on the oxygen tension and hemoglobin saturation of the cytoplasm inside RBCs, and the dissociation kinetics exhibits a nonlinear fashion at different oxygen tensions. To understand how these factors and mechanisms interplay in the oxygen transport process, computational modeling and simulations are favorite since we have a good control of the system parameters and also we can access to the detailed information during the transport process. In this study, we conduct numerical simulations for the blood flow and RBC deformation along a capillary and the oxygen transfer from RBCs to the surrounding tissue. Different values for the hematocrit, arteriole oxygen tension, tissue metabolism rate and hemoglobin concentration and affinity are considered, and the simulated spatial and temporal variations of oxygen concentration are analyzed in conjunction with the nonlinear oxygen-hemoglobin reaction kinetics. Our results show that there are two competing mechanisms for the tissue oxygenation response to a hematocrit increases: the favorite effect of the higher RBC density and the negative effect of the slower RBC motion. Moreover, in the low oxygen situations with RBC oxygen tension less than 50mmHg at capillary inlet, the reduced RBC velocity effect dominates, resulting in a decrease in tissue oxygenation at higher hematocrit. On the opposite, for RBC oxygen tension higher than 50mmHg when entering the capillary, a higher hematocrit is beneficial to the tissue oxygenation. More interestingly, the pivoting arteriole oxygen tension at which the two competing mechanisms switch dominance on tissue oxygenation becomes lower for higher oxygen-hemoglobin affinity and lower hemoglobin concentration. This observation has also been analyzed based on the oxygen supply from RBCs and the oxygen-hemoglobin reaction kinetics. The results and discussions presented in this article could be helpful for a better understanding of oxygen transport in microcirculation.

The study of oxygenation dynamics during experimental tumor growth using frequency-domain diffuse optical spectroscopy

The objective of this work was to study the dynamics and mechanisms of oxygenation changes of an experimental rat tumor Plyss lymphosarcoma in the process of its growth using diffuse optical spectroscopy (DOS). DOS in trans-illumination configuration utilizing high-frequency (140 MHz) modulation of light intensity is used to assess absorption and scattering coefficients averaged over tumor tissue at several wavelengths 684, 794, and 850 nm. Those values were used to assess concentrations of tissue oxyhemoglobin and deoxyhemoglobin and oxygen saturation. During the observation period (from the 5th to the 15th day after transplantation) the tumor volume increased up to 25 times. In the process of tumor growth, a gradual increase in the content of deoxyhemoglobin, a decrease of oxyhemoglobin level, and a decrease of blood oxygen saturation without changes in the level of total tissue hemoglobin concentration were observed. Thus, the main mechanisms of oxygen saturation decrease in the process of tumor growth are associated with two effects: the increase of oxygen consumption rate (demonstrated by the increase of deoxyhemoglobin) and the decrease of oxygen supply (demonstrated by the decrease of oxyhemoglobin).

A neonatal intelligent regulation system based on the combination of mild hypothermia mattress and hyperbaric oxygen chamber: introduction to a patent

Neonatal hypoxic-ischemic encephalopathy (HIE) is a common disease that affects brain function in neonates. At present, mild hypothermia and hyperbaric oxygen therapy are the main methods for the treatment of neonatal HIE; however, they are independent of each other and cannot be combined for synchronous treatment, without monitoring of brain function-related physiological information. In addition, parameter setting of hyperbaric oxygen chamber and mild hypothermia mattress relies on the experience of the medical practitioner, and the parameters remain unchanged throughout the medical process. This article proposes a new device for the treatment of neonatal HIE, which has the modules of hyperbaric oxygen chamber and mild hypothermic mattress, so that neonates can receive the treatment of hyperbaric oxygen chamber and/or mild hypothermic mattress based on their conditions. Meanwhile, it can realize the real-time monitoring of various physiological information, including amplitude-integrated electroencephalogram, electrocardiogram, and near-infrared spectrum, which can monitor brain function, heart rate, rhythm, myocardial blood supply, hemoglobin concentration in brain tissue, and blood oxygen saturation. In combination with an intelligent control algorithm, the device can intelligently regulate parameters according to the physiological information of neonates and give recommendations for subsequent treatment.

Development of a Wireless Multichannel Near-Infrared Spectroscopy Sensor System for Monitoring Muscle Activity

Near-infrared spectroscopy (NIRS) technology is a noninvasive technology that can detect the hemoglobin concentration in the shallow tissue of humans in the form of an optical signal and determine the muscle’s activation state based on the change of hemoglobin concentration. It has a broad application prospect in the biomedical and physiological signal analysis. There are specific requirements for the structure of NIRS sensors for different application scenarios. The muscle synergy theory explains that body movements are often accompanied by the cooperation of many different muscles. Therefore, a multichannel NIRS system is necessary for motion recognition. This article presents a distributed multichannel NIRS system. The wireless communication avoids the interference of signal lines, and the equipped upper computer system can display NIRS signals in real time. Our NIRS sensors have three different wavelengths of near-infrared light (750, 800, and 850 nm) and two photodiodes, which can effectively improve the sampling accuracy of the signal. Experimental verification and evaluation prove that our system’s performance and reliability are better than those of other NIRS systems. Finally, cuff occlusion and hand motion experiments demonstrated that blood flow and oxygen consumption are the two main factors that cause hemoglobin concentration changes. We offer a new scheme for NIRS signal analysis that uses the common mode and difference mode of Hb and HbO2, and the results demonstrate its superior performance. In future work, we will discuss the application and effect of the NIRS system in rehabilitation training.

Noninvasive Dual-Modality Photoacoustic-Ultrasonic Imaging to Detect Mammalian Embryo Abnormalities after Prenatal Exposure to Methylmercury Chloride (MMC): A Mouse Study.

Background:Severe environmental pollution and contaminants left in the environment due to the abuse of chemicals, such as methylmercury, are associated with an increasing number of embryonic disorders. Ultrasound imaging has been widely used to investigate embryonic development malformation and dysorganoplasia in both research and clinics. However, this technique is limited by its low contrast and lacking functional parameters such as the ability to measure blood oxygen saturation () and hemoglobin content (HbT) in tissues, measures that could be early vital indicators for embryonic development abnormality. Herein, we proposed combining two highly complementary techniques into a photoacoustic-ultrasound (PA-US) dual-modality imaging approach to noninvasively detect early mouse embryo abnormalities caused by methylmercury chloride (MMC) in real time.Objectives:This study aimed to assess the use of PA-US dual-modality imaging for noninvasive detection of embryonic toxicity at different stages of growth following prenatal MMC exposure. Additionally, we compared the PA-US imagining results to traditional histological methods to determine whether this noninvasive method could detect early developmental defects in utero.Methods:Different dosages of MMC were administrated to pregnant mice by gavage to establish models of different levels of embryonic malformation. Ultrasound, photoacoustic signal intensity (PSI), blood oxygen saturation (), and hemoglobin content (HbT) were quantified in all experimental groups. Furthermore, the embryos were sectioned and examined for pathological changes.Results:Using PA-US imaging, we detected differences in PSI, , HbT, and heart volume at embryonic day (E)14.5 and E11.5 for low and high dosages of MMC, respectively. More important, our results showed that differences between control and treated embryos identified by in utero PA-US imaging were consistent with those identified in ex vivo embryos using histological methods.Conclusion:Our results suggest that noninvasive dual-modality PA-US is a promising strategy for detecting developmental toxicology in the uterus. Overall, this study presents a new approach for detecting embryonic toxicities, which could be crucial in clinics when diagnosing aberrant embryonic development. https://doi.org/10.1289/EHP8907

Viable Allogeneic Mitochondria Transplantation Improves Gas Exchange and Alveolar-Capillary Permeability in Rats with Endotoxin-Induced Acute Lung Injuries.

Background: Acute lung injuries (ALI) cause disruption of the alveolar-capillary barrier and is the leading cause of death in critically ill patients. This study tested the hypothesis that the administration of freshly isolated viable allogeneic mitochondria can prevent alveolar-capillary barrier injuries at the endothelial level, as mitochondrial dysfunction of the pulmonary endothelium is a critical aspect of ALI progression.Methods: ALI was induced by intratracheal lipopolysaccharide instillation (LPS, 1mg/kg) in anesthetized rats. Mitochondria (100 µg) were isolated from the freshly harvested soleus muscles of naïve rats and stained with a green fluorescence MitoTracker™ dyne. A mitochondria or placebo solution was randomly administered into the jugular veins of the rats at 2 h and 4 h after ALI induction. An arterial blood gas analysis was done 20 h later. The animals were then sacrificed and lung tissues were harvested for analysis.Results: An IVIS Spectrum imaging system was used to obtain ex vivo heart-lung block images and track the enhancement of MitoTracker™ fluorescence in the lungs. Mitochondria transplantation significantly improved arterial oxygen contents (PaO2 and SaO2) and reduced CO2 tension in rats with ALI. Animals with mitochondrial transplants had significantly higher ATP concentrations in their lung tissues. Allogeneic mitochondria transplantation preserved alveolar-capillary barrier function, as shown by a reduction in protein levels in the bronchoalveolar lavage fluid and decreased extravasated Evans blue dyne and hemoglobin content in lung tissues. In addition, relaxation responses to acetylcholine and eNOS expression were potentiated in injured pulmonary arteries and inflammatory cells infiltration into lung tissue was reduced following mitochondrial transplantation.Conclusions: Transplantation of viable mitochondria protects the integrity of endothelial lining of the alveolar-capillary barrier, thereby improving gas exchange during the acute stages of endotoxin-induced ALI. However, the long-term effects of mitochondrial transplantation on pulmonary function recovery after ALI requires further investigation.

Rapid Measurement of Tissue Hemoglobin Concentration Changes by Near-infrared Spectroscopy

Rapid Measurement of Tissue Hemoglobin Concentration Changes by Near-infrared Spectroscopy

Effective method of monitoring cerebral tissue oxygen saturation in cardiac surgery patients by combined use of tNIRS-1 and bispectral index

To continuously and noninvasively monitor the cerebral tissue oxygen saturation (StO2) and hemoglobin concentration (gasHb) in cardiac surgery patients, a method combining the use of a cerebral tissue oximeter using near infrared time-resolved spectroscopy (tNIRS-1) and the bispectral index (BIS) was developed in this study. Moreover, the correlation between the estimated hemoglobin concentration (estHb), measured via tNIRS-1, and the hemoglobin concentration (gasHb), analyzed using a blood gas analyzer, were compared. The relationship between the BIS and gasHb was also examined. Through the comparison of BIS and StO2 (r1), and estHb and gasHb (r2), the correlation between the two was clarified with maximum r1 and r2 values of 0.617 and 0.946, respectively. The relationship between BIS and gasHb (r3), showed that there was a favorable correlation with a maximum r3 value of 0.969. There was also a continuous correlation between BIS and StO2 in patients undergoing cardiac surgery. In addition, a strong correlation was found between estHb and gasHb, and between BIS and gasHb. It was therefore concluded that the combined use of BIS and tNIRS-1 is useful to evaluate cerebral hypoxia, allowing for quick response to cerebral hypoxia and reduction of hemoglobin concentration during the operation.

Monitoring adaptation of skin tissue oxygenation during cycling ergometer exercise by frequency-domain diffuse optical spectroscopy.

In addition to supplying oxygen molecule O2 for metabolic functions during the adaptation to exercise, blood also plays a critical role in heat dissipation for core temperature stabilization. This study investigates the status of hemodynamic oxygenation in the forearm's skin tissue of three participants during a complete ergometer exercise from the resting to exercising, and to recovering conditions using a three-wavelength frequency-domain diffuse reflectance spectroscopy (FD DRS) alongside the monitoring of heartbeat rate and skin temperature. The FD DRS system was synchronized with radiofrequency (RF)-modulated input photon sources and the respective output to extract time-course absorption and scattering coefficients of the skin tissue, which, through the fitting of lambert's law of absorbance, can be used to determine the concentration of oxygenated/deoxygenated hemoglobin molecules, and consequentially, the oxygen saturation of skin tissue and total hemoglobin (THb) concentration. Expressly, a sudden jump in heartbeat rate at the beginning of the exercise, a temporal lag of the rising edge of skin temperature behind that of the THb concentration in the procession of step-wise incremental working intensity, and the uprising of THb in the exhaustion zone in responses to the physiological adaptation to exercise were identified. Finally, conclusive remarks were drawn that the FD DRS system is useful in extracting the hemodynamic properties of forearm skin which is often being neglected in previous exercise physiology studies by DRS-related techniques. The detailed variation of hemodynamic and optical scattering parameters of forearm skin elucidated in the studies can be applied for the analysis of athletes' physiological status, and may be a potential reference for the design of future wearable devices.

Low-intensity pulsed ultrasound enhances angiogenesis in rabbit capsule tissue that acts as a novel vascular bed in vivo.

In vivo prevascularization followed by pedicled transfer has emerged as a promising strategy for tissue engineering in recent years. We recently demonstrated that capsule tissue could serve as a novel axial in vivo vascular bed, although its high-density microvessels could only be maintained for about a week. In this present study, we aimed to demonstrate whether low-intensity pulsed ultrasound (LIPUS) promotes angiogenesis in capsule tissue. After successful induction of capsule tissue using a skin expander, 24 rabbits were randomly divided into the LIPUS group and the control group. The LIPUS group received LIPUS treatment 3 times per week. After 2 and 4 weeks of treatment, angiogenesis of the capsule tissue was assessed using in vivo and in vitro methods, including contrast-enhanced ultrasound (CEUS), photoacoustic imaging (PAI), photoacoustic microscope (PAM), and CD31 immunohistochemistry. In vivo assessments (CEUS, PAI and PAM) showed that tissue perfusion, hemoglobin content and vascular density were all significantly higher in the LIPUS group, which was consistent with CD31 immunohistochemistry. The LIPUS also promoted protein and mRNA expression of vascular endothelial growth factor α (VEGFα) and basic fibroblast growth factor (bFGF) in capsule tissue. Furthermore, cell experiments showed that LIPUS enhanced tube formation of human microvascular endothelial cells (HMECs) and promoted secretion of VEGFα and bFGF. The LIPUS treatment promoted angiogenesis of the capsule tissue by stimulating release of angiogenic factors such as VEGFα and bFGF from endothelial cells, making the capsule tissue more potent and sustained when acting as in vivo vascular bed.

Bedside hyperspectral imaging indicates a microcirculatory sepsis pattern - an observational study

IntroductionMicrocirculatory alterations are key mechanisms in sepsis pathophysiology leading to tissue hypoxia, edema formation, and organ dysfunction. Hyperspectral imaging (HSI) is an emerging imaging technology that uses tissue-light interactions to evaluate biochemical tissue characteristics including tissue oxygenation, hemoglobin content and water content. Currently, clinical data for HSI technologies in critical ill patients are still limited. Methods and analysisTIVITA® Tissue System was used to measure Tissue oxygenation (StO2), Tissue Hemoglobin Index (THI), Near Infrared Perfusion Index (NPI) and Tissue Water Index (TWI) in 25 healthy volunteers and 25 septic patients. HSI measurement sites were the palm, the fingertip, and a suprapatellar knee area. Septic patients were evaluated on admission to the ICU (E), 6 h afterwards (E+6) and three times a day (t3-t9) within a total observation period of 72 h. Primary outcome was the correlation of HSI results with daily SOFA-scores. ResultsSerial HSI at the three measurement sites in healthy volunteers showed a low mean variance expressing high retest reliability. HSI at E demonstrated significantly lower StO2 and NPI as well as higher TWI at the palm and fingertip in septic patients compared to healthy volunteers. StO2 and TWI showed corresponding results at the suprapatellar knee area. In septic patients, palm and fingertip THI identified survivors (E-t4) and revealed predictivity for 28-day mortality (E). Fingertip StO2 and THI correlated to SOFA-score on day 2. TWI was consistently increased in relation to the TWI range of healthy controls during the observation time. Palm TWI correlated positively with SOFA scores on day 3. DiscussionHSI results in septic patients point to a distinctive microcirculatory pattern indicative of reduced skin oxygenation and perfusion quality combined with increased blood pooling and tissue water content. THI might possess risk-stratification properties and TWI could allow tissue edema evaluation in critically ill patients. ConclusionHSI technologies could open new perspectives in microcirculatory monitoring by visualizing oxygenation and perfusion quality combined with tissue water content in critically ill patients – a prerequisite for future tissue perfusion guided therapy concepts in intensive care medicine.