Measurement Of Tissue Oxygenation Research Articles

Quantification of hemi-hepatic ischemia using real-time multispectral oxygenation imaging with single snapshot imaging of optical properties (SSOP).

Identifying liver ischemia is crucial in liver surgery. This study aimed to develop a hemi-hepatic ischemia model for assessing liver ischemia using single snapshot imaging of optical properties (SSOP), a noninvasive optical imaging modality that provides real-time measurements of tissue oxygen saturation (StO2). Twelve swine were randomly assigned to two groups: One undergoing total vascular inflow occlusion (TVIO) and the other undergoing hepatic artery occlusion (HAO). Preoperative 3D CT scans were used to locate the left-sided hepatic arteries and portal veins, which were clamped during surgery. Real-time SSOP imaging was conducted to measure StO2 in three lobes-the left lateral lobe (LL), left medial lobe (LM), and right medial lobe (RM)-as well as capillary lactate levels and Doppler blood flow. Measurements were recorded at baseline (T0), during ischemia (T1, 30min after clamping), and during reperfusion (T2, 30min after declamping). In the TVIO group, SSOP imaging revealed a distinct demarcation line on the liver surface. StO2 levels measured by SSOP significantly decreased from T0 to T1, dropping by 29.8% in the LL (46.0 ± 5.1 vs. 16.2 ± 5.1%, p = 0.011) and 36.3% in the LM (42.7 ± 5.9 vs. 6.4 ± 4.0%, p = 0.001). Additionally, capillary lactate levels increased substantially in the LL (1.3 ± 0.4 vs. 8.5 ± 2.4mmol/L, p = 0.041) and in the LM (1.3 ± 0.4 vs. 8.2 ± 2.1mmol/L, p = 0.021). In contrast, the HAO group showed a less pronounced reduction in StO2: 13.6% in the LL (32.7 ± 6.4 vs. 19.1 ± 5.4%, p = 0.007) and 19.8% in the LM (35.3 ± 8.2 vs. 15.5 ± 5.8%, p = 0.011), with no significant increase in capillary lactate levels. An inverse correlation was found between StO2 and capillary lactate levels (r = -0.76, p < 0.001). SSOP is a real-time, contrast-free imaging technique that effectively evaluates liver ischemia by accurately measuring tissue oxygenation, as validated by perfusion biomarkers.

Using noninvasive imaging to assess manual lymphatic drainage on lymphatic/venous responses in a spaceflight analog

This retrospective case series (clinicaltrials.gov NCT06405282) used noninvasive imaging devices (NIID) to assess the effect of manual lymphatic drainage (MLD) on dermal/venous fluid distribution, perfusion, and temperature alterations of the head, neck, upper torso, and legs while in the 6-degree head-down tilt validated spaceflight analog. A lymphatic fluid scanner measured tissue dielectric constant levels. Near-infrared spectroscopy assessed perfusion, by measuring tissue oxygenation saturation. Long-wave infrared thermography measured tissue temperature gradients. Fifteen healthy, university students participated. NIID assessments were taken 1 minute after assuming the HDT position and then every 30 minutes, with MLD administered from 180 to 195 minutes. Subjects returned to the sitting position and were assessed at post-225 min NIID demonstrated significant changes from baseline (p < 0.01), although these changes at areas of interest varied. MLD had a reverse effect on all variables. NIID assessment supported the potential use of MLD to mitigate fluid shifts during a spaceflight analog.

Neuromonitoring in the ICU: noninvasive and invasive modalities for critically ill children and neonates.

Critically ill children are at risk of neurologic dysfunction and acquiring primary and secondary brain injury. Close monitoring of cerebral function is crucial to prevent, detect, and treat these complications. A variety of neuromonitoring modalities are currently used in pediatric and neonatal ICUs. These include noninvasive modalities, such as electroencephalography, transcranial Doppler, and near-infrared spectroscopy, as well as invasive methods including intracranial pressure monitoring, brain tissue oxygen measurement, and cerebral microdialysis. Each modality offers unique insights into neurologic function, cerebral circulation, or metabolism to support individualized neurologic care based on a patient's own physiology. Utilization of these modalities in ICUs results in reduced neurologic injury and mortality and improved neurodevelopmental outcomes. Monitoring of neurologic function can significantly improve care of critically ill children. Additional research is needed to establish normative values in pediatric patients and to standardize the use of these modalities.

Impact of Peripheral Angioplasty on Wound Oxygenation and Healing in Patients with Chronic Limb-Threatening Ischemia Measured by Near-Infrared Spectroscopy.

Managing chronic limb-threatening ischemia (CLTI) is challenging due to difficulties in assessing tissue oxygen saturation in ulcers. Near-infrared spectroscopy (NIRS) is a non-invasive method for measuring tissue oxygen saturation (StO2). This study evaluated the effects of endovascular treatment (EVT) on StO2 and wound healing in CLTI patients, comparing NIRS to standard ankle-brachial index (ABI) measurements. Using the Duesseldorf PTA Registry, 43 CLTI patients were analyzed: 27 underwent EVT, and 16 received conservative treatment. ABI assessed macrocirculation, while NIRS measured wound, wound area, and mean foot StO2 at baseline, post-EVT, and four-month follow-up. Wound severity was classified by wound area and wound, ischemia, and foot infection (WIfI) score. Wound StO2 increased significantly (median (interquartile range (IQR)), 38 (49.3) to 60 (34.5)%, p = 0.004), as did wound area StO2 (median (IQR), 70.9 (21.6) to 72.8 (18.3)%, p < 0.001), with no significant changes in the control group by four-month follow-up. Wound area decreased significantly after EVT (mean ± SD, 343.1 ± 267.8 to 178.1 ± 268.5 mm2, p = 0.01) but not in the control group. Changes in wound StO2, wound area StO2, and WIfI score correlated with wound area reduction, unlike ABI. This small exploratory study shows that NIRS-measured StO2 improvements after EVT correlate with reduced wound area and WIfI scores, highlighting NIRS as a potential enhancement for CLTI wound management in addition to ABI.

Application of Near Infrared Spectroscopy to Enhance Safety and Individualize Distraction of Severely Contracted Joints in Far-Advanced Dupuytren's Disease.

Background: Slow distraction of contracted joints is a well-established treatment in far-advanced stages of Dupuytren's disease (DD). To assess finger perfusion and avoid malperfusion, we studied near infrared spectroscopy (NIRS) to evaluate the maximum extent of distraction that would not harm microcirculation to the finger. This technique also allows an optimized treatment in accordance with sufficient blood perfusion during distraction. Methods: Eligible patients with stage IV finger contractures who needed treatment for Dupuytren's contracture were included and prospectively investigated. The operation was performed with local anaesthesia. First, the Dupuytren strand of the treated finger was dissected in the palm to allow distraction. Under X-ray control, the distraction device was applied. Then, slow distraction of the treated joint was performed to evaluate the finger perfusion. To assess perfusion of the treated finger, NIRS was used to measure tissue oxygen saturation. If impaired finger perfusion was detected, traction was reduced until sufficient oxygen levels and perfusion patterns were reestablished. Results: NIRS was performed after application of the distraction device in seven cases. We treated six male and one female patient (mean age 70 years, range 51-80 years). Rapid distraction resulted in malperfusion of the treated fingers. Using NIRS proved to render reliable and reproducible information on finger perfusion and oxygenation in all seven patients. Conclusions: Application of NIRS enhances safety in the treatment of far-advanced DD finger contractures with an external skeletal distraction device. It is non-invasive, reproducible, easy to use and allows for an individualized adapted distraction velocity.

Skin Pigmentation Affects ViOptix T.Ox Performance in Variably Pigmented Preclinical Model of Flap Ischemia and Congestion.

Free flap monitoring is more difficult in patients with dark skin because ischemia and congestion can be masked by pigmentation. For this reason, adjunct methods such as cutaneous near-infrared spectroscopy are of elevated importance in patients with highly pigmented skin. The purpose of this experiment is to determine if ViOpitx T.Ox performance is affected by cutaneous pigmentation. Swine with naturally occurring areas of nonpigmented and pigmented skin were used. Pigmentation of each animal was assessed using spectrophotometry and histopathology. During normoxemia, tissue oxygenation (StO2) measurements were taken of nonpigmented and pigmented skin using the T.Ox device. A bicolor pedicled rectus abdominis myocutaneous flap was raised, and T.Ox probe was adhered to adjacent areas of opposite coloration on the same flap. StO2 was measured continuously during reversible episodes of flap ischemia and congestion (n = 4 swine, n = 6 flaps). There was not a significant difference between baseline StO2 values of nonpigmented (49% ± 7.9%) and pigmented skin (47% ± 6.2%). The absolute change in StO2 was significantly larger during both ischemia (6%) and congestion (16%) in nonpigmented skin compared with adjacent pigmented skin. T.Ox detects flap ischemia and congestion in both highly pigmented and nonpigmented skin. However, surgeons need to be aware that StO2 changes related to complete flap ischemia or congestion may be much more subtle than what is seen in nonpigmented skin. This study establishes a novel internally controlled porcine model that isolates the impact of skin pigmentation when assessing cutaneous devices measuring tissue oxygenation.

Estimation of differential pathlength factor from NIRS measurement in skeletal muscle

The utilization of continuous wave (CW) near-infrared spectroscopy (NIRS) device to measure non-invasively muscle oxygenation in healthy and disease states is limited by the uncertainties related to the differential path length factor (DPF). DPF value is required to quantify oxygenated and deoxygenated heme groups’ concentration changes from measurement of optical densities by NIRS. An integrated approach that combines animal and computational models of oxygen transport and utilization was used to estimate the DPF value in situ. The canine model of muscle oxidative metabolism allowed measurement of both venous oxygen content and tissue oxygenation by CW NIRS under different oxygen delivery conditions. The experimental data obtained from the animal model were integrated in a computational model of O2 transport and utilization and combined with Beer-Lambert law to estimate DPF value in contracting skeletal muscle. A 2.1 value was found for DPF by fitting the mathematical model to the experimental data obtained in contracting muscle (T3) (Med.Sci.Sports.Exerc.48(10):2013–2020,2016). With the estimated value of DPF, model simulations well predicted the optical density measured by NIRS on the same animal model but with different blood flow, arterial oxygen contents and contraction rate (J.Appl.Physiol.108:1169–1176, 2010 and 112:9–19,2013) and demonstrated the robustness of the approach proposed in estimating DPF value. The approach used can overcome the semi-quantitative nature of the NIRS and estimate non-invasively DPF to obtain an accurate concentration change of oxygenated and deoxygenated hemo groups by CW NIRS measurements in contracting skeletal muscle under different oxygen delivery and contraction rate.

AngioMT: A MATLAB based 2D image-to-physics tool to predict oxygen transport in vascularized microphysiological systems.

Microphysiological models (MPS) are increasingly getting recognized as in vitro preclinical systems of pathophysiology and drug discovery. However, there is also a growing need to adapt and advance MPS to include the physiological contributions of the capillary vascular dynamics, because they undergo angiogenesis or vasculogenesis to deliver soluble oxygen and nutrients to its organs. Currently, the process of formation of microvessels in MPS is measured arbitrarily, and vascularized MPS do not include oxygen measurements in their analysis. Sensing and measuring tissue oxygen delivery is extremely difficult because it requires access to opaque and deep tissue, and/or requires extensive integration of biosensors that makes such systems impractical to use in the real world. Here, a finite element method-based oxygen transport program, called AngioMT, is built in MATLAB. AngioMT processes the routinely acquired 2D confocal images of microvascular networks in vitro and solves physical equations of diffusion-reaction dominated oxygen transport phenomena. This user-friendly image-to-physics transition in AngioMT is an enabling tool of MPS analysis because unlike the averaged morphological measures of vessels, it provides information of the spatial transport of oxygen both within the microvessels and the surrounding tissue regions. Further, it solves the more complex higher order reaction mechanisms which also improve the physiological relevance of this tool when compared directly against in vivo measurements. Finally, the program is applied in a multicellular vascularized MPS by including the ability to define additional organ/tissue subtypes in complex co-cultured systems. Therefore, AngioMT serves as an analytical tool to enhance the predictive power and performance of MPS that incorporate microcirculation.

Ultrasound Diagnosis and Near-Infrared Spectroscopy in the Study of Encephalopathy in Neonates Born under Asphyxia: Narrative Review.

Brain injury resulting from adverse events during pregnancy and delivery is the leading cause of neonatal morbidity and disability. Surviving neonates often suffer long-term motor, sensory, and cognitive impairments. Birth asphyxia is among the most common causes of neonatal encephalopathy. The integration of ultrasound, including Doppler ultrasound, and near-infrared spectroscopy (NIRS) offers a promising approach to understanding the pathology and diagnosis of encephalopathy in this special patient population. Ultrasound diagnosis can be very helpful for the assessment of structural abnormalities associated with neonatal encephalopathy such as alterations in brain structures (intraventricular hemorrhage, infarcts, hydrocephalus, white matter injury) and evaluation of morphologic changes. Doppler sonography is the most valuable method as it provides information about blood flow patterns and outcome prediction. NIRS provides valuable insight into the functional aspects of brain activity by measuring tissue oxygenation and blood flow. The combination of ultrasonography and NIRS may produce complementary information on structural and functional aspects of the brain. This review summarizes the current state of research, discusses advantages and limitations, and explores future directions to improve applicability and efficacy.

Age and Handgrip Strength Induce Differences in Micro- and Macro-Vascular Responses

Purpose: Handgrip (HG) strength is a potent predictor of cardiovascular disease (CVD) and all-cause mortality. Advances in technology have provided novel assessments of peripheral microvascular and macrovascular health and function. These advances include measurements of skeletal muscle tissue oxygenation (StO2, %) with near-infrared spectroscopy (NIRS) during vascular occlusion tests (VOT) as well as carotid-femoral pulse-wave velocity (cfPWV), which is the current gold-standard to measure aortic stiffness. Although NIRS-VOT and cfPWV have been shown to change across the lifespan, it is unknown if these variables are sensitive to group differences as defined by HG strength. Therefore, our purpose was to examine mean differences in NIRS-VOT parameters and cfPWV between groups of low and high HG strength. We hypothesized that individuals with lower HG strength would exhibit lower vascular function. Methods: 67 adults were separated into age groups: young (19 – 40 yr), midlife (41 – 64 yr), and older (≥65 yr). Groups were divided into low and high strength at the median for HG strength, and quasi-balanced based on biological sex. This resulted in six participant groups (e.g., midlife low strength). The VOT included 3 min of rest, 5 min of ischemia, and 3 min of reperfusion to determine indices of reactive hyperemia. Indices included the initial (i.e., first 10 s) rate of re-saturation (upslope) and the maximal StO2 (StO2max) percent following ischemia. Aortic stiffness was defined as cfPWV using the time difference between the appearance of the carotid and femoral pulses. Separate 2×3 between factor (HG by Age Group) ANOVAs were conducted for each outcome. A p≤0.05 was considered significant, and data were presented as mean ± SD. Results: For upslope, there was a significant interaction (p=0.042, ηp2=0.078), and follow-up analyses revealed for young and midlife adults the high HG group exhibited greater upslopes than the low strength group (young: 2.24±0.9 vs. 1.64±0.7 and midlife: 2.21±0.9 vs. 1.59±0.7%∙s−1). There was no significant interaction (p=0.360) for StO2max, but there was a significant main effect (p&lt;0.001) of Age such that it progressively decreased across the lifespan (83.9 ± 2.0 &gt; 80.7 ± 2.3 &gt; 77.3 ± 2.8%). Similarly, cfPWV exhibited a significant main effect (p&lt;0.001; ηp2 =0.429) of Age indicating aortic stiffness worsened with age, independent of HG strength. Conclusions: These results indicated that upslope was sensitive to group differences in HG strength, but only in the young and midlife age groups. For StO2max and cfPWV, age differences appeared to elicit a stronger effect than HG strength. The current findings suggested that HG strength may be most reflective of a specific portion of the vascular tree, while the initial rate of re-saturation and StO2max may be influenced by different mechanisms associated with reactive hyperemia. Notably, the participants in this study were relatively healthy based on being free of any chronic disease. Future work is necessary to determine the predictive power of NIRS-VOT parameters for future onset of CVD. We would like to thank the American Physiology Society for support and the University of South Alabama for allowing us to use its facilities. We would also like to thank all of the participants who agreed to adhere to the protocol and procedures of this study. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Measuring tissue oxygen saturation in the orad intestinal segment during equine colic surgery may aid in predicting the occurrence of postoperative ileus.

To assess the histological injury and intestinal microperfusion measured by laser Doppler flowmetry and spectrophotometry (LDFS) of the small intestine orad to a strangulation during colic surgery. Horses with naturally occurring small intestinal strangulations undergoing colic surgery were included. In this prospective clinical trial, intestinal tissue oxygen saturation (tSO2) and tissue blood flow (tBF) were measured by LDFS orad to the strangulation following release of the strangulation (n = 18). The number of horses with postoperative reflux (POR) and the cases that survived until discharge were compared between groups using Fisher's exact test (P < .05). Intestinal biopsies were taken in cases that underwent intestinal resection or intraoperative euthanasia (n = 28). Measurements were compared between injured and noninjured segments with a Mann-Whitney U or t test. The tSO2 and tBF of the orad intestine were lower than previously reported in healthy horses. Horses with low tSO2 of < 35% were significantly more likely to suffer from POR (6/6 cases) compared to cases with tSO2 > 69% (1/6). The number of horses that survived were not statistically different between these groups (2/6 and 6/6). All horses with mucosal injury developed POR (6/6), which was significantly more likely compared to horses without mucosal injury (3/13). No significant difference in tSO2 or tBF could be found between the segments with and without histological injury. The results suggest that measuring tSO2 in the orad segment during colic surgery may aid in predicting postoperative issues.

Noninvasive estimation of skeletal muscle oxygen consumption rate and microvascular reactivity in chronic stroke survivors using near-infrared spectroscopy.

Understanding post-stroke changes in skeletal muscle oxidative metabolism and microvascular reactivity could help create therapeutic targets that optimize rehabilitative interventions. Due to disuse atrophy, we hypothesized that basal muscle oxygen consumption rate and microvascular endothelial function would be impaired in the tibialis anterior (TA) muscle of the affected leg of chronic stroke survivors compared with the nonaffected leg and versus matched controls. Fifteen chronic stroke survivors (10 females) and 15 matched controls (9 females) completed this study. A near-infrared spectroscopy oximeter measured tissue oxygen saturation (StO2) of the TA in both legs of stroke survivors and the dominant leg of controls. A cuff was placed around the thigh and inflated to 225 mmHg for 5 min while StO2 was continuously measured. The rate of change in StO2 was calculated during cuff occlusion and immediately post-cuff release. The rate of oxygen desaturation was similar between the legs of the stroke survivors (paretic -0.12 ± 0.04%·s-1 vs. nonparetic -0.16 ± 011%·s-1; P = 0.49), but the paretic leg had a reduced desaturation rate versus controls (-0.25 ± 0.18%·s-1; P = 0.007 vs. paretic leg). After cuff release, there was a greater oxygen resaturation rate in the nonparetic leg compared with the paretic leg (3.13 ± 2.08%·s-1 vs. 1.60 ± 1.11%·s-1, respectively; P = 0.01). The control leg had a similar resaturation rate versus the nonparetic leg (control = 3.41 ± 1.79%·s-1; P = 0.69) but was greater than the paretic leg (P = 0.003). The TA in the paretic leg had an impaired muscle oxygen consumption rate and reduced microvascular endothelial function compared with controls.NEW & NOTEWORTHY Secondary consequences of stroke are not well described. In this study, we show that basal muscle oxidative consumption and microvascular endothelial function are reduced in the paretic tibialis anterior muscle of chronic stroke survivors compared with matched controls using near-infrared spectroscopy and the vascular occlusion technique. There was a moderately strong correlation between microvascular endothelial function and paretic leg strength.

Paraspinal muscle oxygenation and mechanical efficiency are reduced in individuals with chronic low back pain

This study aimed to compare the systemic and local metabolic responses during a 5-min trunk extension exercise in individuals with chronic low back pain (CLBP) and in healthy individuals. Thirteen active participants with CLBP paired with 13 healthy participants performed a standardised 5-min trunk extension exercise on an isokinetic dynamometer set in continuous passive motion mode. During exercise, we used near-infrared spectroscopy to measure tissue oxygenation (TOI) and total haemoglobin-myoglobin (THb). We used a gas exchange analyser to measure breath-by-breath oxygen consumption (V̇O2) and carbon dioxide produced (V̇CO2). We also calculated mechanical efficiency. We assessed the intensity of low back pain sensation before and after exercise by using a visual analogue scale. In participants with CLBP, low back pain increased following exercise (+ 1.5 units; p < 0.001) and THb decreased during exercise (− 4.0 units; p = 0.043). Paraspinal muscle oxygenation (65.0 and 71.0%, respectively; p = 0.009) and mechanical efficiency (4.7 and 5.3%, respectively; p = 0.034) were both lower in participants with CLBP compared with healthy participants. The increase in pain sensation was related to the decrease in tissue oxygenation (R2 = − 0.420; p = 0.036). Decreases in total haemoglobin-myoglobin and mechanical efficiency could involve fatigability in exercise-soliciting paraspinal muscles and, therefore, exacerbate inabilities in daily life. Given the positive correlation between tissue oxygenation and exercise-induced pain exacerbation, muscle oxygenation may be related to persisting and crippling low back pain.

Near-infrared spectroscopy for kidney oxygen monitoring in a porcine model of hemorrhagic shock, hemodilution, and REBOA

Acute kidney injury is a common complication of trauma and hemorrhagic shock. In a porcine model of hemorrhagic shock, resuscitative endovascular balloon aortic occlusion (REBOA) and hemodilution, we hypothesized that invasive kidney oxygen concentration measurements would correlate more strongly with noninvasive near infra-red spectroscopy (NIRS) oxygen saturation measurements when cutaneous sensors were placed over the kidney under ultrasound guidance compared to placement over the thigh muscle and subcutaneous tissue. Eight anesthetized swine underwent hemorrhagic shock 4 of which were resuscitated with intravenous fluids prior to the return of shed blood (Hemodilution protocol) and 4 of which underwent REBOA prior to resuscitation and return of shed blood (REBOA protocol). There was a moderate correlation between the NIRS and kidney tissue oxygen measurements (r = 0.61 p < 0.001; r = 0.67 p < 0.001; r = 0.66 p < 0.001for left kidney, right kidney, and thigh NIRS respectively). When the animals were separated by protocol, the Hemodilution group showed a weak or nonsignificant correlation between NIRS and kidney tissue oxygen measurements (r = 0.10 p < 0.001; r = 0.01 p = 0.1007; r = 0.28 p < 0.001 for left kidney, right kidney, and thigh NIRS respectively). This contrasts with the REBOA group, where left and right kidney as well as thigh NIRS were moderately correlated with kidney tissue oxygen (r = 0.71 p < 0.001; r = 0.74 p < 0.001; r = 0.70 p < 0.001; for left kidney, right kidney, and thigh NIRS respectively). There was a strong correlation between both kidney NIRS signals and thigh NIRS measurements (r = 0.85 p < 0.001; r = 0.88 p < 0.001;for left kidney vs thigh and right kidney vs thigh respectively). There was also a strong correlation between left and right kidney NIRS (r = 0.90 p < 0.001). These relationships were maintained regardless of the resuscitation protocol. These results suggest that kidney NIRS measurements were more closely related to thigh NIRS measurements than invasive kidney tissue oxygen concentration.

The influence of carbon dioxide on cerebral metabolism and oxygen consumption: combining multimodal monitoring with dynamic systems modelling.

Hypercapnia increases cerebral blood flow. The effects on cerebral metabolism remain incompletely understood although studies show an oxidation of cytochrome c oxidase, Complex IV of the mitochondrial respiratory chain. Systems modelling was combined with previously published non-invasive measurements of cerebral tissue oxygenation, cerebral blood flow, and cytochrome c oxidase redox state to evaluate any metabolic effects of hypercapnia. Cerebral tissue oxygen saturation and cytochrome oxidase redox state were measured with broadband near infrared spectroscopy and cerebral blood flow velocity with transcranial Doppler ultrasound. Data collected during 5-min hypercapnia in awake human volunteers were analysed using a Fick model to determine changes in brain oxygen consumption and a mathematical model of cerebral hemodynamics and metabolism (BrainSignals) to inform on mechanisms. Either a decrease in metabolic substrate supply or an increase in metabolic demand modelled the cytochrome oxidation in hypercapnia. However, only the decrease in substrate supply explained both the enzyme redox state changes and the Fick-calculated drop in brain oxygen consumption. These modelled outputs are consistent with previous reports of CO2 inhibition of mitochondrial succinate dehydrogenase and isocitrate dehydrogenase. Hypercapnia may have physiologically significant effects suppressing oxidative metabolism in humans and perturbing mitochondrial signalling pathways in health and disease.

Rate of body weight gain during early gestation in F0 beef heifers has effects that extend multigenerationally to the F2 fetuses.

Our aim was to investigate the effects of maternal (F0) body weight (BW) gain during the first 84 d of gestation on body composition, ovarian reserve, and hormonal and metabolic parameters of breeding-age F1 heifers, as well as the BW and morphometry of F2 fetuses. The study also evaluated the effect of maternal BW gain (F0) on the mRNA relative abundance of the small intestine of both F1 heifers and F2 fetuses. Crossbred Angus heifers (F0; n = 100) were managed to gain 0.20kg/d (low gain [LG], n = 50) or 0.75kg/d (moderate gain [MG], n = 50) for the first 84 d of gestation. Subsequently, F0 dams were managed on a common forage-based diet for the rest of gestation until the weaning of the F1 offspring. At 15 mo of age, a subset of F1 heifers was randomly selected for the current experiment (n = 8 LG and n = 8 MG). Heifers were bred via artificial insemination (AI; day 0), then harvested on day 84 of gestation. On days -10, 42, and 84, BW was recorded, and blood was collected and analyzed for concentrations of glucose, non-esterified fatty acids, progesterone, insulin, and insulin-like growth factor-1. The weight of F1 carcasses, organs, gravid uteri, and F2 fetuses and organs were recorded at harvest. Visible follicles were counted on F1 ovaries at harvest, and histology was used to count microscopic follicles. Liver and jejunal samples from F1 heifers were collected to measure tissue oxygen consumption and jejunal samples from F1 heifers and F2 fetuses were collected for mRNA relative abundance analysis. BW of F1 heifers from MG dams tended to be 12kg greater (P = 0.06) than for F1 heifers from LG dams. Concentrations of glucose were greater (P = 0.03) in F1 heifers from the MG group, with no differences in other blood metabolites or follicular populations (P ≥ 0.16). Interestingly, mammary glands were heavier (P = 0.05), and placentas and body depth tended to be heavier and greater, respectively (P ≤ 0.10), for F2 fetuses from F0 LG heifers. Oxygen consumption in the liver and jejunum, as well as mRNA relative abundance in the jejunum of F1 heifers, were not affected by F0 rate of gain (P ≥ 0.16). However, the NDUFC1, SDHA, UQCR1, and PPARG genes were upregulated (P ≤ 0.05) in the jejunum of F2 fetuses from the LG group. In conclusion, BW gain of F0 heifers during early gestation exerts subtle effects on pre-breeding BW and blood metabolites in F1 offspring, with impacts present in F2 placenta, mammary gland, and intestine.

Microvascular Shunts, Intracranial Pressure, and the Impact of Drag-Reducing Polymers.

In the 50 years of my membership in ISOTT, I, Edwin M Nemoto, have enjoyed the application of many of the technologies developed in our society including microelectrodes for pH, PO2, and near-infrared spectroscopy (NIRS) in the measurement of tissue oxygenation and metabolism. The greatest joy has been the number of great scientists I have had the pleasure of knowing and exchanging scientific ideas with across the United States, Europe, and Asia. This will be the enduring legacy of ISOTT for me personally as we continue beyond our half-century existence.Every organ in our body, including the tegmentum, is endowed with microvascular shunts (MVS), which may be involved in physiological regulation, i.e. temperature regulation or pathophysiological responses to tissue injury and oedema. MVS that open in response to increased capillary resistance and tissue oedema in the brain, heart, kidneys, liver, and muscles conduct neither nutrient nor gas exchange with tissue promoting tissue oedema in a vicious cycle. Pharmacologic arteriolar vasodilation cannot correct the MVS flow as may occur after a stroke or traumatic brain injury because pan arteriolar vasodilation would shunt flow to the normal tissue and away from the injured brain in a "reverse" steal or a "Robin Hood" phenomenon. A high molecular weight (4000kDa) drag-reducing polymer (DRP) of polyethylene oxide or Lamiflo™ enhances blood flow by altering the physical dynamics of red blood cells (RBC) and blood flow, increasing the shear rate in the microvasculature and capillaries where shear rate is highest as it is inversely proportional to the 3rd power of blood vessel diameter. The shear rate sensed on the endothelium through the glycocalyx exerts precise control of endothelial function, including endothelial water permeability, nitric oxide synthase activity, lymphocyte adhesion to and transport across the endothelium, and microglial activation, all in response to low endothelial shear rate. DRP has proven effective in reversing MVS flow and increasing capillary flow in haemorrhagic shock, myocardial ischaemia, stroke, renal ischaemia, traumatic brain injury, stroke, sepsis, and Alzheimer's Disease. Our aim is to establish the universality of MVS in the pathogenesis of vascular disease and in taking DRP to clinical treatment of vascular diseases.

Near-Infrared Spectroscopy Analysis of Triceps Brachii Muscle Oxygenation During Sprinting in Wheelchair Basketball Players: A Pilot Study.

The purpose of this study was to clarify the characteristics of muscle fatigue by measuring the oxygenation of muscles during wheelchair sprinting in wheelchair basketball players, using near-infrared spectroscopy (NIRS). We believe that this information will be helpful in planning rehabilitation and training programmes.Five male wheelchair basketball players (mean age 30.0±12.0years, mean height 166.0±12.1cm, and mean weight 61.0±15.8kg) participated in this study.These participants performed six 20 m sprint tests after warming up. NIRS measurements were obtained at rest before the start of exercise, during sprinting movements, and during the recovery time after sprinting. Measurements were taken using a wireless NIRS device (PortaMon, Artinis, The Netherlands; sampling rate, 10Hz) with a single-channel system for tissue oxygenation measurements. The NIRS sensor was applied to the triceps muscle on the participant's dominant arm and fixed with an upper arm supporter. The measurement data were imported into a dedicated computer and the tissue saturation index (TSI) was calculated. Statistical analysis was performed using the Friedman test to compare the TSI before sprinting and at each sprint, and a post hoc Bonferroni test was conducted.Compared to the pre-sprint measurements, TSI significantly decreased during sprints second, fourth, and fifth.In the present study, changes in the oxygen status of the triceps muscle during wheelchair driving varied greatly among individuals, and a tendency was observed towards the oxygen saturation being lowest by the fourth sprint, with the decrease being suppressed from this point on.

Evaluation of Morlet Wavelet Analysis for Artifact Detection in Low-Frequency Commercial Near-Infrared Spectroscopy Systems.

Regional cerebral oxygen saturation (rSO2), a method of cerebral tissue oxygenation measurement, is recorded using non-invasive near-infrared Spectroscopy (NIRS) devices. A major limitation is that recorded signals often contain artifacts. Manually removing these artifacts is both resource and time consuming. The objective was to evaluate the applicability of using wavelet analysis as an automated method for simple signal loss artifact clearance of rSO2 signals obtained from commercially available devices. A retrospective observational study using existing populations (healthy control (HC), elective spinal surgery patients (SP), and traumatic brain injury patients (TBI)) was conducted. Arterial blood pressure (ABP) and rSO2 data were collected in all patients. Wavelet analysis was determined to be successful in removing simple signal loss artifacts using wavelet coefficients and coherence to detect signal loss artifacts in rSO2 signals. The removal success rates in HC, SP, and TBI populations were 100%, 99.8%, and 99.7%, respectively (though it had limited precision in determining the exact point in time). Thus, wavelet analysis may prove to be useful in a layered approach NIRS signal artifact tool utilizing higher-frequency data; however, future work is needed.

Arch watch: current approaches and opportunities for improvement.

Coarctation of the aorta (CoA) is a ductus arteriosus (DA)-dependent form of congenital heart disease (CHD) characterized by narrowing in the region of the aortic isthmus. CoA is a challenging diagnosis to make prenatally and is the critical cardiac lesion most likely to go undetected on the pulse oximetry-based newborn critical CHD screen. When undetected CoA causes obstruction to blood flow, life-threatening cardiovascular collapse may result, with a high burden of morbidity and mortality. Hemodynamic monitoring practices during DA closure (known as an "arch watch") vary across institutions and existing tools are often insensitive to developing arch obstruction. Novel measures of tissue oxygenation and oxygen deprivation may improve sensitivity and specificity for identifying evolving hemodynamic compromise in the newborn with CoA. We explore the benefits and limitations of existing and new tools to monitor the physiological changes of the aorta as the DA closes in infants at risk of CoA.