Tissue Oximetry Research Articles

A Comparative Study of the Effect of Nasal Intermittent Positive Pressure Ventilation and Nasal Continuous Positive Airway Pressure on the Regional Brain Tissue Oximetry in Premature Newborns Weighing

Background:Near-infrared spectroscopy (NIRS) provides the capability of monitoring oxygenation levels in cerebral microscopic vessels, enabling the operator to observe the spontaneous changes in the levels of hemoglobin concentration in tissue and interpret the resulting fluctuations. The current study tried to investigate whether brain's autoregulatory mechanisms in premature newborns have the potential to prevent the adverse effects caused by asynchronous changes of pressure in the rib cage. Therefore, NIRS method was applied to newborns that were alternatively shifted from nasal continuous positive airway pressure (nCPAP) to nasal intermittent positive pressure ventilation (NIPPV) and vice versa.Methods:This study was done as a crossover randomized clinical trial on 30 very low-weight newborns under nCPAP, who had received surfactant as a result of respiratory distress syndrome diagnosis, from April 2015 to April 2016, in Isfahan Shahid Beheshti Educational Hospital. The newborns were 72 h old, experiencing continuous distending pressure (CDP) = 4–6 cmH2O with FiO2 = 30%–40%. The respiratory support would alternate from nCPAP to NIPPV and vice versa (with indicators of expiratory PAP (EPAP) = CDP and inspiratory PAP = EPAP + 4 cmH2O), and the cerebral regional oxygen saturation (CrSO2) was monitored using NIRS.Results:The study results indicated that newborns significantly showed higher levels of CrSO2(84.93, P = 0.005) and oxygenation (94.63, P = 0.007) under nCPAP rather than NIPPV (82.43 and 93.43, respectively). The respiratory rate was also meaningfully slower when newborns were under nCPAP (P = 0.013).Conclusions:This study revealed that applying NIPPV may have an unfavorable effect on the premature newborn's brain tissue perfusion. However, more studies are needed to ensure solid outcomes.

Effects of Acute, Profound Hypoxia on Healthy Humans: Implications for Safety of Tests Evaluating Pulse Oximetry or Tissue Oximetry Performance.

Extended periods of oxygen deprivation can produce acidosis, inflammation, energy failure, cell stress, or cell death. However, brief profound hypoxia (here defined as SaO2 50%-70% for approximately 10 minutes) is not associated with cardiovascular compromise and is tolerated by healthy humans without apparent ill effects. In contrast, chronic hypoxia induces a suite of adaptations and stresses that can result in either increased tolerance of hypoxia or disease, as in adaptation to altitude or in the syndrome of chronic mountain sickness. In healthy humans, brief profound hypoxia produces increased minute ventilation and increased cardiac output, but little or no alteration in blood chemistry. Central nervous system effects of acute profound hypoxia include transiently decreased cognitive performance, based on alterations in attention brought about by interruptions of frontal/central cerebral connectivity. However, provided there is no decrease in cardiac output or ischemia, brief profound hypoxemia in healthy humans is well tolerated without evidence of acidosis or lasting cognitive impairment.

How to manage blood pressure after brain injury?

Manipulation of blood pressure (BP) is a mainstay of therapy in patients with acute brain injury (ABI). In the early emergent phase (first hours from injury), depending on intracranial pathology, BP manipulation aims to: 1) limit the progression of parenchymal hematomas or hemorrhagic transformation (in patients with ischemic/hemorrhagic stroke and aneurysmal subarachnoid hemorrhage [SAH]), and 2) attenuate hypoperfusion and secondary cerebral ischemic insults (in patients with traumatic brain injury [TBI]). During the intensive care unit (ICU) phase, BP management is primarily focused at identifying the so-called "optimal" BP/cerebral perfusion pressure (CPP), i.e. the threshold of mean arterial pressure (MAP)/CPP to prevent secondary cerebral ischemia. BP augmentation is also an essential component of the medical management of delayed cerebral ischemia following SAH. Increasing clinical data support the use of surrogate monitoring modalities of cerebral perfusion (including trans-cranial Doppler and brain tissue oximetry) to indentify BP/CPP targets in ABI patients. We reviewed herein the actual evidence regarding BP control in the early phase after ABI and recent clinical investigations using multimodal monitoring to optimize CPP and BP in severe ABI patients. The main purpose of this review is to provide a pragmatic approach of BP management, taking into account the timing of injury and differences in brain pathologies.

Neurophysiological Intraoperative Monitoring During Aortic Arch Surgery.

Circulatory management during replacement of the aortic arch is complex and involves a period of circulatory arrest to provide a bloodless field during arch vessel anastomosis. To guard against ischemic brain injury, tissue metabolic demand is reduced by systemically cooling the patient prior to circulatory arrest. Neurophysiological intraoperative monitoring (NIOM) is often used during the course of these procedures to provide contemporaneous assessment of brain status to help direct circulatory management decisions and detect brain ischemia. In this review, we discuss the characteristics of electrocerebral activity through the process of cooling, circulatory arrest, and rewarming as depicted through commonly used NIOM modalities, including electroencephalography and peripheral nerve somatosensory-evoked potentials. Attention is directed toward the role NIOM has traditionally played during deep hypothermic circulatory arrest, where it is used to define the point of electrocerebral inactivity or maximal cerebral metabolic suppression prior to initiating circulatory arrest while also discussing the evolving utility of NIOM when systemic circulatory arrest is initiated at more moderate degrees of hypothermia in conjunction with regional brain perfusion. The use of cerebral tissue oximetry by near-infrared spectroscopy as an alternative NIOM modality during surgery of the aortic arch is addressed as well. Finally, special considerations for NIOM and the detection of spinal cord ischemia during hybrid aortic arch repair and emerging operative techniques are also discussed.

Placental tissue oxygen saturation measured using tissue oximetry is related to placental gas exchange

Placental tissue oxygen saturation measured using tissue oximetry is related to placental gas exchange

Cerebral Oximetry in Ugandan Children With Severe Anemia

Severe anemia, defined as a hemoglobin level of less than 5.0 g/dL, affects millions of children worldwide. The brain has a high basal demand for oxygen and is especially vulnerable to hypoxemia. Previous studies have documented neurocognitive impairment in children with severe anemia. Data on cerebral tissue oxygenation in children with severe anemia and their response to blood transfusion are limited. To measure hemoglobin saturation in cerebral tissue (cerebral tissue oxygen saturation [tSo2]) before, during, and after blood transfusion in a cohort of children presenting to hospital with severe anemia. This was a prospective, observational cohort study conducted from February 2013 through May 2015 and analyzed in July 2015 at a university hospital pediatric acute care facility in Kampala, Uganda, of 128 children, ages 6 to 60 months who were enrolled in a larger clinical trial, with a presenting hemoglobin level of less than 5.0 g/dL and a blood lactate level greater than 5mM. Most children had either malaria or sickle cell disease. Red blood cell (RBC) transfusion given as 10 mL/kg over 120 minutes. Clinical and laboratory characteristics of children with pretransfusion cerebral tSo2 levels less than 65%, 65% to 75%, and greater than 75%. Change in cerebral tSo2 as a result of transfusion. Of 128 children included in the study, oximetry results in 8 cases were excluded owing to motion artifacts; thus, 120 were included in this analysis. Cerebral tSo2 values prior to transfusion ranged from 34% to 87% (median, 72%; interquartile range [IQR], 65%-76%). Eighty-one children (67%) demonstrated an initial cerebral tSo2 level (≤75%) corresponding to an oxygen extraction ratio greater than 0.36. Patients with sickle cell disease (n = 17) and malaria (n = 15) contributed in nearly equal numbers to the subgroup with an initial cerebral tSo2 (<65%). The level of consciousness, hemoglobin concentration, blood lactate level, and thigh muscle tSo2 level were poor predictors of cerebral oxygen saturation. Following RBC transfusion, the median (IQR) cerebral tSo2 level increased to 78% (73%-82%) (P < .001), but 21% of children failed to achieve a tSo2 level greater than 75%. Severe anemia in children is frequently associated with low cerebral oxygenation levels as measured by near-infrared spectroscopy. Hemoglobin level and lactate concentration did not predict low cerebral tSo2 levels. Cerebral tSo2 levels increase with RBC transfusion with different patterns of response. More studies are needed to evaluate the use of noninvasive cerebral tissue oximetry in the care of children with severe anemia.

Abstract: A Novel Text Messaging Alert System Used with Continuous Tissue Oximetry Monitoring to Improve Free Flap Outcomes

INTRODUCTION: The time to detection of vascular compromise is a significant predictor of free flap salvage outcomes as early re-exploration has been shown to improve the salvage rate for failing free flaps. Continuous transcutaneous near-infrared tissue oximetry is an objective, quantitative method of detecting flap vascular compromise and has been shown to allow earlier re-exploration and higher salvage rates than clinical assessment alone. We designed a novel text messaging system to improve communication using tissue oximetry monitoring. MATERIALS AND METHODS: A retrospective review was performed of a prospectively collected database of all microsurgical breast reconstructions from 2008 to 2015. A novel text messaging system was introduced in 2013 and programmed to send text messages alert when the tissue oximetry readings suggested potential flap compromise based on established thresholds. Patient demographics and complications, including rate of re-exploration and flap loss (partial and total) were assessed. RESULTS: There were 900 autologous microsurgical breast free flaps during the study period: 614 were monitored with standard clinical monitoring and tissue oximetry compared with 286 flaps with the additional text messaging system. There were 27 unplanned returns to the operating room in the tissue oximetry group and 5 in the text messaging group with 1 complete flap loss in each group. Re-exploration occurred sooner as a result of these text message alerts (17.5 vs. 26.6 hours postoperatively), however, did not achieve statistical significance. CONCLUSIONS: We were able to demonstrate the use of a novel text messaging system for tissue oximetry. This alert system shows promise in identifying impending flap loss with rapid notification of the surgical team. Improved communication and identification of failing free flaps will allow for an even further improvement of salvage rates. DISCLOSURE/FINANCIAL SUPPORT:This work was not supported by any external sources of funding. None of the authors have any financial interest in any of the products, devices, or drugs mentioned in this manuscript.

Regional Oxygen Saturation Index: A Novel Criterion for Free Flap Assessment Using Tissue Oximetry.

Tissue oximetry is a useful tool for postoperative free flap monitoring. Reported criterion values have been accurate; however, there are various complicated author-dependent criteria, and sometimes it is too late for flap salvage. The authors offer a new, simple criterion for faster and accurate detection of perfusion problems. Intraoperatively, perfusion areas of various free perforator flaps were assessed by both indocyanine green angiography and regional oxygen saturation. The elevated flap was categorized into the early-stained area, the delayed-stained area, and the no-stained area by indocyanine green angiography. The regional oxygen saturation index (regional oxygen saturation on the flap on the control nondissected portion) of each area was calculated. Postoperative continuous flap monitoring was conducted, recording the value of the regional oxygen saturation index at the early-stained area. The blood glucose measurement index was also recorded periodically. In 60 cases of perforator-based free flaps, intraoperative indocyanine green areas were significantly correlated with the values of regional oxygen saturation index. The postoperative regional oxygen saturation index showed very stable values in various types of perforator flaps, provided that no vascular problem occurred, and it never went below 0.75. When vascular problems occurred, the regional oxygen saturation index dropped below 0.75 in all three cases before the blood glucose measurement index and the absolute value of regional oxygen saturation dropped below the criterion value. The regional oxygen saturation index may be a simple and fast criterion for detecting vascular problems following free flap reconstruction compared with existing criteria. Diagnostic, II.

Abstract: Ex Vivo Normothermic Limb Perfusion and Limb Specific Monitoring Evaluation of Perfusion Quality

PURPOSE: Ischemia time represents a significant limitation for successful extremity replantation and transplantation because of the rapid deterioration of ischemic muscle. Static cold storage (SCS) of the limb is the standard clinical practice. Normothermic ex vivo perfusion system has the potential to prolong viability providing oxygen and metabolites after limb amputation. The aim of our study was to establish a perfusion protocol with limb specific diagnostic tools to evaluate the quality and uniformity of perfusion in an ex vivo model. METHODS: A total of 18 swine limbs were perfused, five of them followed the final, optimized protocol. Limbs were perfused at 39OC for twelve hours using an oxygenated colloid solution with packed red blood cells. Glucose and electrolytes were kept within physiologic range by the addition of hypertonic solution or by partial hypotonic perfusate exchanges. Limb specific perfusion quality was assessed by muscle contractility upon electrical nerve stimulation, compartment pressure, creatine kinase(CK) and myoglobin concentrations, tissue oxygen saturation (near infrared spectroscopy), indocyanine green (ICG) angiography, and infrared radiation emission by thermographic imaging. RESULTS: All five limbs reached the 12 hour perfusion target maintaining normal compartment pressure (16.23 ± 7.94 mmHg), minimal weight increase (0.54%±0.07), mean muscle temperature of 33.54 ± 1.5oC, and tissue oximetry readings of 59.67%±10.21. Average values of final myoglobin and CK were 875 ± 291.4 ng/mL, and 53344 ± 14850.34 U/L, respectively. Muscle movement was present in all limbs until cessation of perfusion. Differences in uniformity and quality of distal perfusion were demonstrated using thermography and angiography imaging after 12 hours of perfusion. Colder areas on Thermographic imaging correlated to mal perfused areas on ICG angiography. CONCLUSIONS: Ex-vivo normothermic limb perfusion preserves limb physiology and function for at least 12 hours. Thermography and ICG angiography are valuable tools in the assessment of limb perfusion quality with the advantage of providing an immediate evaluation which allows for the visual identification of perfusion gradients and regions of mal-perfusion. Muscle contraction upon nerve stimulation, a uniform physiologic temperature and tissue oxygenation, and the distal dye distribution on angiography identify a successful perfusion. These methods may have important future implications on the decision to transplant or replant a perfused limb. Myoglobin and CK concentration increased in all limbs during ex vivo perfusion, but the functional significance of this is still to be determined.

Blood transfusion in preterm infants improves intestinal tissue oxygenation without alteration in blood flow.

The objective of the study was to investigate the splanchnic blood flow velocity and oximetry response to blood transfusion in preterm infants according to postnatal age. Preterm infants receiving blood transfusion were recruited to three groups: 1-7 (group 1; n = 20), 8-28 (group 2; n = 21) and ≥29 days of life (group 3; n = 18). Superior mesenteric artery (SMA) peak systolic (PSV) and diastolic velocities were measured 30-60 min pre- and post-transfusion using Doppler ultrasound scan. Splanchnic tissue haemoglobin index (sTHI), tissue oxygenation index (sTOI) and fractional tissue oxygen extraction (sFTOE) were measured from 15-20 min before to post-transfusion using near-infrared spectroscopy. The mean pretransfusion Hb in group 1, 2 and 3 was 11, 10 and 9 g/dl, respectively. The mean (SD) pretransfusion SMA PSV in group 1, 2 and 3 was 0·63 (0·32), 0·81 (0·33) and 0·97 (0·40) m/s, respectively, and this did not change significantly following transfusion. The mean (SD) pretransfusion sTOI in group 1, 2 and 3 was 36·7 (19·3), 44·6 (10·4) and 41·3 (10·4)%, respectively. The sTHI and sTOI increased (P < 0·01), and sFTOE decreased (P < 0·01) following transfusion in all groups. On multivariate analysis, changes in SMA PSV and sTOI following blood transfusion were not associated with PDA, feeding, pretransfusion Hb and mean blood pressure. Pretransfusion baseline splanchnic tissue oximetry and blood flow velocity varied with postnatal age. Blood transfusion improved intestinal tissue oxygenation without altering mesenteric blood flow velocity irrespective of postnatal ages.

Near-infrared Spectroscopy Monitoring During Cardiac Arrest: A Systematic Review and Meta-analysis.

Tissue oximetry using near-infrared spectroscopy (NIRS) is a noninvasive monitor of cerebral oxygenation. This new technology has been used during cardiac arrest (CA) because of its ability to give measures in low-blood-flow situations. The aim of this study was to assess the evidence regarding the association between the types of NIRS measurements (mean, initial, and highest values) and resuscitation outcomes (return of spontaneous circulation [ROSC], survival to discharge, and good neurologic outcome) in patients undergoing cardiopulmonary resuscitation. This review was registered (Prospero CRD42015017380) and is reported as per the PRISMA guidelines. Medline, Embase, and CENTRAL were searched. All studies, except case reports and case series of fewer than five patients, reporting on adults that had NIRS monitoring during CA were eligible for inclusion. Two reviewers assessed the quality of the included articles and extracted the data. The outcome effect was standardized using standardized mean difference (SMD). Twenty nonrandomized observational studies (15 articles and five conference abstracts) were included in this review, for a total of 2,436 patients. We found a stronger association between ROSC and mean NIRS values (SMD=1.33; 95% confidence interval [CI]=0.92 to 1.74) than between ROSC and initial NIRS measurements (SMD=0.51; 95% CI=0.23 to 0.78). There was too much heterogeneity among the highest NIRS measurements group to perform meta-analysis. Only two of the 75 patients who experienced ROSC had a mean NIRS saturation under 30%. Patients who survived to discharge and who had good neurologic outcome displayed superior combined initial and mean NIRS values than their counterparts (SMD=1.63; 95% CI=1.34 to 1.92; and SMD=2.12; 95% CI=1.14 to 3.10). Patients with good resuscitation outcomes have significantly higher NIRS saturations during resuscitation than their counterparts. The types of NIRS measurements during resuscitation influenced the association between ROSC and NIRS saturation. Prolonged failure to obtain a NIRS saturation higher than 30% may be included in a multimodal approach to the decision of terminating resuscitation efforts (Class IIb, Level of Evidence C-Limited Data).

A Novel Free Flap Monitoring System Using Tissue Oximetry with Text Message Alerts.

Background The time to detection of vascular compromise is a significant predictor of free flap salvage outcomes as early reexploration improves salvage rates. Continuous transcutaneous near-infrared tissue oximetry is an objective, quantitative method of detecting flap vascular compromise and has been shown to allow earlier reexploration and higher salvage rates than clinical assessment alone. We designed a novel text messaging system to improve communication using tissue oximetry monitoring. Methods A retrospective review was performed of a prospectively collected database of all microsurgical breast reconstructions from 2008 to 2015. A novel text messaging system was introduced in 2013 and programmed to send text messages alert when the tissue oximetry readings suggested potential flap compromise based on established thresholds. Patient demographics and complications, including rate of reexploration and flap loss were assessed. Results There were 900 autologous microsurgical breast free flaps during the study period: 614 were monitored with standard clinical monitoring and tissue oximetry compared with 286 flaps with the additional text messaging system. There were 27 unplanned returns to the operating room in the tissue oximetry group and 5 in the text messaging group with 1 complete flap loss in each group. Reexploration occurred sooner as a result of these text message alerts (17.5 vs. 26.6 hours postoperatively), however, it did not achieve statistical significance. Conclusions We were able to demonstrate the use of a novel text messaging system for tissue oximetry. This alert system shows promise in identifying impending flap loss with rapid notification of the surgical team.

LO041: Predicting the return of spontaneous circulation using near-infrared spectroscopy monitoring: a systematic review and meta-analysis

Introduction: Tissue oximetry using near-infrared spectroscopy (NIRS) is a non-invasive monitor of cerebral oxygenation. This new technology has been used during cardiac arrest because of its ability to give measures in low blood flow situations. The aim of this systematic review was to assess the evidence regarding the association between NIRS values and resuscitation outcomes in patients undergoing cardiopulmonary resuscitation. We hypothesized that higher NIRS values would be associated with better outcomes and that the strength of that association would differ depending on the timing of the NIRS measurements. Methods: This review was registered (Prospero CRD42015017380) and is reported as per the PRISMA guidelines. Medline, Embase and CENTRAL were searched from their inception to September 18th, 2015 using a specifically designed search strategy. Grey literature was also searched using Web of Science and Google Scholar. NIRS manufacturers and authors of included citations were contacted to inquire on unpublished results. Finally, the references of all retained articles were reviewed in search of additional relevant studies. Studies reporting NIRS monitoring in adults during cardiac arrest were eligible for inclusion. Case reports and case series of fewer than five patients were automatically excluded. Two reviewers assessed the quality of included articles and extracted the data. Results: Out of 3275 unique citations, 19 non-randomized observational studies (15 articles and four conference abstracts) were included in this review, for a total of 2436 patients. Six studies were evaluated at low risk of bias, nine at intermediate risk and four at high risk. We found a stronger association between the return of spontaneous circulation (ROSC) and the highest NIRS value measured during resuscitation (standard mean deviation (SMD) 3.46 (95%CI 2.31-4.62)) than between ROSC and the mean NIRS measures (SMD 1.33 (95%CI 0.92-1.74)) which was superior to the one between ROSC and initial measures (SMD 0.45 (95%CI 0.02-0.88)). Conclusion: Patients with good outcomes have significantly higher NIRS value during resuscitation than their counterparts. The association between ROSC and NIRS measurements was influenced the timing of measurements during resuscitation.

Pathophysiologic Mechanisms of Cerebral Ischemia and Diffusion Hypoxia in Traumatic Brain Injury.

Combined oxygen 15-labeled positron emission tomography (15O PET) and brain tissue oximetry have demonstrated increased oxygen diffusion gradients in hypoxic regions after traumatic brain injury (TBI). These data are consistent with microvascular ischemia and are supported by pathologic studies showing widespread microvascular collapse, perivascular edema, and microthrombosis associated with selective neuronal loss. Fluorine 18-labeled fluoromisonidazole ([18F]FMISO), a PET tracer that undergoes irreversible selective bioreduction within hypoxic cells, could confirm these findings. To combine [18F]FMISO and 15O PET to demonstrate the relative burden, distribution, and physiologic signatures of conventional macrovascular and microvascular ischemia in early TBI. This case-control study included 10 patients who underwent [18F]FMISO and 15O PET within 1 to 8 days of severe or moderate TBI. Two cohorts of 10 healthy volunteers underwent [18F]FMISO or 15O PET. The study was performed at the Wolfson Brain Imaging Centre of Addenbrooke's Hospital. Cerebral blood flow, cerebral blood volume, cerebral oxygen metabolism (CMRO2), oxygen extraction fraction, and brain tissue oximetry were measured in patients during [18F]FMISO and 15O PET imaging. Similar data were obtained from control cohorts. Data were collected from November 23, 2007, to May 22, 2012, and analyzed from December 3, 2012, to January 6, 2016. Estimated ischemic brain volume (IBV) and hypoxic brain volume (HBV) and a comparison of their spatial distribution and physiologic signatures. The 10 patients with TBI (9 men and 1 woman) had a median age of 59 (range, 30-68) years; the 2 control cohorts (8 men and 2 women each) had median ages of 53 (range, 41-76) and 45 (range, 29-59) years. Compared with controls, patients with TBI had a higher median IBV (56 [range, 9-281] vs 1 [range, 0-11] mL; P < .001) and a higher median HBV (29 [range, 0-106] vs 9 [range, 1-24] mL; P = .02). Although both pathophysiologic tissue classes were present within injured and normal appearing brains, their spatial distributions were poorly matched. When compared with tissue within the IBV compartment, the HBV compartment showed similar median cerebral blood flow (17 [range, 11-40] vs 14 [range, 6-22] mL/100 mL/min), cerebral blood volume (2.4 [range, 1.6- 4.2] vs 3.9 [range, 3.4-4.8] mL/100 mL), and CMRO2 (44 [range, 27-67] vs 71 [range, 34-88] μmol/100 mL/min) but a lower oxygen extraction fraction (38% [range, 29%-50%] vs 89% [range, 75%-100%]; P < .001), and more frequently showed CMRO2 values consistent with irreversible injury. Comparison with brain tissue oximetry monitoring suggested that the threshold for increased [18F]FMISO trapping is probably 15 mm Hg or lower. Tissue hypoxia after TBI is not confined to regions with structural abnormality and can occur in the absence of conventional macrovascular ischemia. This physiologic signature is consistent with microvascular ischemia and is a target for novel neuroprotective strategies.

Cerebral oximetry in preterm infants: an agenda for research with a clear clinical goal.

Preterm birth constitutes a major cause of death before 5 years of age and it is a major cause of neurodevelopmental impairment across the world. Preterm infants are most unstable during the transition between fetal and newborn life during the first days of life and most brain damage occurs in this period. The brain of the preterm infant is accessible for tissue oximetry by near-infrared spectroscopy. Cerebral oximetry has the potential to improve the long-term outcome by helping to tailor the support of respiration and circulation to the individual infant's needs, but the evidence is still lacking. The goals for research include testing the benefit and harms of cerebral oximetry in large-scale randomized trials, improved definition of the hypoxic threshold, better understanding the effects of intensive care on cerebral oxygenation, as well as improved precision of oximeters and calibration among devices or standardization of values in the hypoxic range. These goals can be pursued in parallel.

Craniofacial tissue oxygen saturation is associated with blood pH using an examiner's finger-mounted tissue oximetry in mice.

Although fetal scalp blood sampling is an examination to assess fetal acidosis during the intrapartum period, it has not been widely used by obstetricians because of its invasiveness. We have developed a small, portable oximetry with a sensor attached to the examiner's finger. Our previous report using this oximetry concluded that fetal head tissue oxygen saturation (StO 2 StO2 ) correlated with umbilical cord artery blood pH. We investigated whether the association between StO 2 StO2 and blood pH in mice could be validated using this oximetry. Eleven the Institute for Cancer Research (ICR) mice were measured using a near-infrared spectroscopy probe at the craniofacial site in a closed polyethylene bag while changing the oxygen concentration. A total of nine blood samples were collected and analyzed for pH. The StO 2 StO2 and tissue blood pH showed a strong positive correlation (r=0.90 r=0.90 and P=0.0009 P=0.0009 ). The StO 2 StO2 and total hemoglobin index also showed a positive correlation (r=0.84 r=0.84 and P=0.0049 P=0.0049 ). Thus, the results of the present study support those of our previous report on clinical cases and allow examiners to easily check the status of fetal acidosis. Fetal management using this oximetry might gain popularity with obstetricians in the near future.

Preliminary investigation of multispectral retinal tissue oximetry mapping using a hyperspectral retinal camera

Oximetry measurement of principal retinal vessels represents a first step towards understanding retinal metabolism, but the technique could be significantly enhanced by spectral imaging of the fundus outside of main vessels. In this study, a recently developed Hyperspectral Retinal Camera was used to measure relative oximetric (SatO2) and total hemoglobin (HbT) maps of the retina, outside of large vessels, in healthy volunteers at baseline (N = 7) and during systemic hypoxia (N = 11), as well as in patients with glaucoma (N = 2). Images of the retina, on a field of view of ∼30°, were acquired between 500 and 600 nm with 2 and 5 nm steps, in under 3 s. The reflectance spectrum from each pixel was fitted to a model having oxy- and deoxyhemoglobin as the main absorbers and scattering modeled by a power law, yielding estimates of relative SatO2 and HbT over the fundus. Average optic nerve head (ONH) saturation over 8 eyes was 68 ± 5%. During systemic hypoxia, mean ONH saturation decreased by 12.5% on average. Upon further development and validation, the relative SatO2 and HbT maps of microvasculature obtained with this imaging system could ultimately contribute to the diagnostic and management of diseases affecting the ONH and retina.

Does Increased Experience with Tissue Oximetry Monitoring in Microsurgical Breast Reconstruction Lead to Decreased Flap Loss? The Learning Effect

Early studies have shown that near-infrared monitoring with tissue oximetry shows promise in providing earlier detection of free flap vascular compromise. However, large-scale clinical evaluation of this technology on flap outcome has not previously been established. This study examines the effect of tissue oximetry on flap reexploration rates and salvage over a 10-year period. The learning curve for this new technology is also assessed. A retrospective review was performed of prospectively maintained data on all microsurgical breast reconstructions performed at an academic institution from 2004 to 2014. Patients were divided into two separate cohorts--standard clinical monitoring and standard clinical monitoring plus tissue oximetry--and rates of reexploration and flap salvage were compared. Subgroup analysis (tertiles) was performed to assess outcomes with increasing experience. A total of 380 flaps (36.2 percent) received standard clinical monitoring, and 670 flaps (63.8 percent) received additional tissue oximetry monitoring. The rate of flap salvage before implementation of tissue oximetry monitoring was 57.7 percent and increased to 96.6 percent (p < 0.001). The number of complete flap losses decreased from 11 (2.9 percent) to one (0.1 percent) with the use of tissue oximetry (p < 0.001). Subgroup analysis demonstrated significantly fewer reexplorations in the third tertile. Inclusion of continuous tissue oximetry in the postoperative monitoring protocol of microsurgical breast reconstruction is associated with significantly improved salvage rates and fewer flap losses. Furthermore, learning curve assessment demonstrates that use of tissue oximetry can decrease the rate of reexploration over time.

Event-related changes of the prefrontal cortex oxygen delivery and metabolism during driving measured by hyperspectral fNIRS.

Recent technological advancements in optical spectroscopy allow for the construction of hyperspectral (broadband) portable tissue oximeters. In a series of our recent papers we have shown that hyperspectral NIRS (hNIRS) has similar or better capabilities in the absolute tissue oximetry as frequency-domain NIRS, and that hNIRS is also very efficient in measuring temporal changes in tissue hemoglobin concentration and oxygenation. In this paper, we extend the application of hNIRS to the measurement of event-related hemodynamic and metabolic functional cerebral responses during simulated driving. In order to check if hNIRS can detect event-related changes in the brain, we measured the concentration changes of oxygenated (HbO2) and deoxygenated (HHb) hemoglobin and of the oxidized state of cytochrome c oxidase, on the right and left prefrontal cortices (PFC) simultaneously during simulated driving on sixteen healthy right-handed participants (aged between 22-32). We used our in-house hNIRS system based on a portable spectrometer with cooled CCD detector and a driving simulator with a fully functional steering wheel and foot pedals. Each participant performed different driving tasks and participants were distracted during some driving conditions by asking general knowledge true/false questions. Our findings suggest that more complex driving tasks (non-distracted) deactivate PFC while distractions during driving significantly activate PFC, which is in agreement with previous fMRI results. Also, we found the changes in the redox state of the cytochrome C oxidase to be very consistent with those in the concentrations of HbO2 and HHb. Overall our findings suggest that in addition to the suitability of absolute tissue oximetry, hyperspectral NIRS may also offer advantages in functional brain imaging. In particular, it can be used to measure the metabolic functional brain activity during actual driving.

Tissue oximetry in anaesthesia and intensive care.

Conventional monitoring during surgery and intensive care is not sufficiently sensitive to detect acute changes in vital organs perfusion, while its good quality is critical for maintaining their function. Disturbed vital organ perfusion may lead to the development of postoperative complications, including neurological sequel and renal failure. Near-infra-red spectroscopy (NIRS) represents one of up-to-date techniques of patient monitoring which is commonly used for the assessment of brain oximetry in thoracic aorta surgery, and - increasingly more often -in open-heart surgery. Algorithms for maintaining adequate brain saturation may result in a decrease of neurological complications and cognitive dysfunction following cardiac surgery. The assessment of kidney and visceral perfusion with tissue oximetry is gaining increasing interest during pediatric cardiac surgery. Attempts at decreasing complications by the use of brain oximetry during carotid endarterectomy, as well as thoracic and abdominal surgery demonstrated conflicting results. In recent years NIRS technique was proposed as a tool for muscle perfusion assessment under short term ischemia and reperfusion, referred to as vascular occlusion test (VOT). This monitoring extension allows for the identification of early disturbances in tissue perfusion. Results of recent studies utilizing VOT suggest that the muscle saturation decrease rate is reduced in septic shock patients, while decreased speed of saturation recovery on reperfusion is related to disturbed microcirculation. Being non-invasive and feasible technique, NIRS offers an improvement of preoperative risk assessment in cardiac surgery and promises more comprehensive intraoperative and ICU patient monitoring allowing for better outcome.