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Muscle hyperemia in exercise is usually the combined result of increased cardiac output and local muscle vasodilation, with the latter reflecting muscle's capacity for increased blood perfusion to support exercise. In this study, we aim to quantify muscle's vasodilation capability with dynamic BOLD imaging. A deoxyhemoglobin-kinetics model is proposed to analyze dynamic BOLD signals acquired during exercise recovery, deriving a hyperemia index (HI) for a muscle group of interest. We demonstrated the method's validity with calf muscles of healthy subjects who performed plantar flexion for muscle stimulation. In a test with exercise load incrementally increasing from 0 to 16 lbs., gastrocnemius HI showed considerable variance among the 4 subjects, but with a consistent trend, i.e. low at light load (e.g. 0–6 lbs) and linearly increasing at heavy load. The high variability among different subjects was confirmed with the other 10 subjects who exercised with a same moderate load of 8 lbs., with coefficient of variance among subjects' medial gastrocnemius 87.8%, lateral gastrocnemius 111.8% and soleus 132.3%. These findings align with the fact that intensive exercise induces high muscle hyperemia, but a comparison among different subjects is hard to make, presumably due to the subjects' different rate of oxygen utilization. For the same 10 subjects who exercised with load of 8 lbs., we also performed dynamic contrast enhanced (DCE) MRI to measure muscle perfusion (F). With a moderate correlation of 0.654, HI and F displayed three distinctive responses of calf muscles: soleus of all the subjects were in the cluster of low F and low HI, and gastrocnemius of most subjects had high F and either low or high HI. This finding suggests that parameter F encapsulates blood flow through vessels of all sizes, but BOLD-derived HI focuses on capillary flow and therefore is a more specific indicator of muscle vasodilation. In conclusion, the proposed hyperemia index has the potential of quantitatively assessing muscle vasodilation induced with exercise. [ABSTRACT FROM AUTHOR]

Abstract Background Circulatory shock, defined as decreased tissue perfusion, leading to inadequate oxygen delivery to meet cellular metabolic demands, remains a common condition with high morbidity and mortality. Rapid restitution and restoration of adequate tissue perfusion are the main treatment goals. To achieve this, current hemodynamic strategies focus on adjusting global physiological variables such as cardiac output (CO), hemoglobin (Hb) concentration, and arterial hemoglobin oxygen saturation (SaO2). However, it remains a challenge to identify optimal targets for these global variables that best support microcirculatory function. Weighting up the risks and benefits is especially difficult for choosing the amount of oxygen supplementation in critically ill patients. This review assesses the physiological basis for oxygen delivery to the tissue and provides an overview of the relevant literature to emphasize the importance of considering risks and benefits and support decision making at the bedside. Physiological premises Oxygen must reach the tissue to enable oxidative phosphorylation. The human body timely detects hypoxia via different mechanisms aiming to maintain adequate tissue oxygenation. In contrast to the pulmonary circulation, where the main response to hypoxia is arteriolar vasoconstriction, the regulatory mechanisms of the systemic circulation aim to optimize oxygen availability in the tissues. This is achieved by increasing the capillary density in the microcirculation and the capillary hematocrit thereby increasing the capacity of oxygen diffusion from the red blood cells to the tissue. Hyperoxia, on the other hand, is associated with oxygen radical production, promoting cell death. Current state of research Clinical trials in critically ill patients have primarily focused on comparing macrocirculatory endpoints and outcomes based on stroke volume and oxygenation targets. Some earlier studies have indicated potential benefits of conservative oxygenation. Recent trials show contradictory results regarding mortality, organ dysfunction, and ventilatory-free days. Empirical studies comparing various targets for SaO2, or partial pressure of oxygen indicate a U-shaped curve balancing positive and negative effects of oxygen supplementation. Conclusion and future directions To optimize risk–benefit ratio of resuscitation measures in critically ill patients with circulatory shock in addition to individual targets for CO and Hb concentration, a primary aim should be to restore tissue perfusion and avoid hyperoxia. In the future, an individualized approach with microcirculatory targets will become increasingly relevant. Further studies are needed to define optimal targets.

Abstract Purpose Currently, there is no marker of efficacy of red blood cell (RBC) transfusion. This study describes the impact of RBC transfusion on mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in critically ill patients with anemia. Methods Critically ill patients with a hemoglobin concentration 7 g/dL), we saw a dissociation of the effect of RBC transfusion on mitoPO2 versus on mitoVO2 values. MitoPO2 and mitoVO2 values were not associated with commonly used parameters of tissue perfusion and oxygenation. Conclusion RBC transfusion did not alter mitoPO2 and mitoVO2 in critically ill patients with anemia. MitoPO2 and mitoVO2 values were not notably associated with Hb concentrations, parameters of severity of illness and markers of tissue perfusion or oxygenation. Given the high baseline value, it cannot be excluded nor confirmed whether RBC can improve low mitoPO2. Trial registration number NCT03092297 (registered 27 March 2017)

Fournier’s gangrene is a mortal surgical emergency characterized by rapidly spreading soft tissue necrosis between fascial planes in the perineum and genital area. The goal of treatment is early debridement of necrotic tissues to improve tissue oxygenation. In the treatment of this case, somatic oximetry monitoring, which is a non-invasive method, was applied in addition to hemodynamic monitoring to evaluate the effectiveness of fluids, antibiotics and debridements more closely. In the efficacy of the treatment, it was observed that rSO2 values correlated with other laboratory and follow-up parameters.

Background: Circulatory shock, defined as decreased tissue perfusion, leading to inadequate oxygen delivery to meet cellular metabolic demands, remains a common condition with high morbidity and mortality. Rapid restitution and restoration of adequate tissue perfusion are the main treatment goals. To achieve this, current hemodynamic strategies focus on adjusting global physiological variables such as cardiac output (CO), hemoglobin (Hb) concentration, and arterial hemoglobin oxygen saturation (SaO2). However, it remains a challenge to identify optimal targets for these global variables that best support microcirculatory function. Weighting up the risks and benefits is especially difficult for choosing the amount of oxygen supplementation in critically ill patients. This review assesses the physiological basis for oxygen delivery to the tissue and provides an overview of the relevant literature to emphasize the importance of considering risks and benefits and support decision making at the bedside. Physiological premises: Oxygen must reach the tissue to enable oxidative phosphorylation. The human body timely detects hypoxia via different mechanisms aiming to maintain adequate tissue oxygenation. In contrast to the pulmonary circulation, where the main response to hypoxia is arteriolar vasoconstriction, the regulatory mechanisms of the systemic circulation aim to optimize oxygen availability in the tissues. This is achieved by increasing the capillary density in the microcirculation and the capillary hematocrit thereby increasing the capacity of oxygen diffusion from the red blood cells to the tissue. Hyperoxia, on the other hand, is associated with oxygen radical production, promoting cell death. Current state of research: Clinical trials in critically ill patients have primarily focused on comparing macrocirculatory endpoints and outcomes based on stroke volume and oxygenation targets. Some earlier studies have indicated potential benefits of conservative oxygenation. Recent trials show contradictory results regarding mortality, organ dysfunction, and ventilatory-free days. Empirical studies comparing various targets for SaO2, or partial pressure of oxygen indicate a U-shaped curve balancing positive and negative effects of oxygen supplementation. Conclusion and future directions: To optimize risk–benefit ratio of resuscitation measures in critically ill patients with circulatory shock in addition to individual targets for CO and Hb concentration, a primary aim should be to restore tissue perfusion and avoid hyperoxia. In the future, an individualized approach with microcirculatory targets will become increasingly relevant. Further studies are needed to define optimal targets. [ABSTRACT FROM AUTHOR]

Purpose: Currently, there is no marker of efficacy of red blood cell (RBC) transfusion. This study describes the impact of RBC transfusion on mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in critically ill patients with anemia. Methods: Critically ill patients with a hemoglobin concentration < 10 g/dL, for whom a single RBC unit had been ordered, were included. MitoPO2 was measured with the COMET device immediately before RBC transfusion, 0.5 h, 1 h, 3 h, and 24 h after RBC transfusion. MitoVO2 was calculated from dynamic mitoPO2 measurements during cessation of local oxygen supply. Results: Sixty-three patients participated, median age 64.0 (interquartile range (IQR) 52.3–72.8) years, median hemoglobin concentration before transfusion 7.4 (IQR 7.1–7.7) g/dL. Median mitoPO2 values were 55.0 (IQR 49.6–63.0) mmHg before RBC transfusion, 51.0 (IQR 41.5–61.2) directly after and 67.3 (IQR 41.6–83.7) at 24 h after RBC transfusion. Median mitoVO2 values were 3.3 (IQR 2.1–5.9) mmHg/s before RBC transfusion, 3.7 (IQR 2.0–5.1) mmHg/s directly after, and 3.1 (IQR 2.5–4.8) mmHg/s 24 h after RBC transfusion. In the higher Hb concentration group (> 7 g/dL), we saw a dissociation of the effect of RBC transfusion on mitoPO2 versus on mitoVO2 values. MitoPO2 and mitoVO2 values were not associated with commonly used parameters of tissue perfusion and oxygenation. Conclusion: RBC transfusion did not alter mitoPO2 and mitoVO2 in critically ill patients with anemia. MitoPO2 and mitoVO2 values were not notably associated with Hb concentrations, parameters of severity of illness and markers of tissue perfusion or oxygenation. Given the high baseline value, it cannot be excluded nor confirmed whether RBC can improve low mitoPO2. Trial registration number NCT03092297 (registered 27 March 2017) [ABSTRACT FROM AUTHOR]

The effect of bronchodilators is mainly assessed with forced expiratory volume in 1 s (FEV1) in chronic obstructive pulmonary disease (COPD). Their impact on oxygenation and lung periphery is less known. Our objective was to compare the action of long-acting β2-agonists (LABA-olodaterol) and muscarinic antagonists (LAMA-tiotropium) on tissue oxygenation in COPD, considering their impact on proximal and peripheral ventilation as well as lung perfusion. FEV1, Helium slope (SHe) from a single-breath washout test (SHe decreases reflecting a peripheral ventilation improvement), frequency dependence of resistance (R5-R19), area under reactance (AX), lung capillary blood volume (Vc) from double diffusion (DLNO/DLCO), and transcutaneous oxygenation (TcO2) were measured before and 2 h post-LABA (day 1) and LAMA (day 3) in 30 patients with COPD (FEV1 54 ± 18% pred; GOLD A 31%/B 48%/E 21%) after 5–7 days of washout, respectively. We found that TcO2 increased more (P = 0.03) after LAMA (11 ± 12% from baseline, P < 001) compared with LABA (4 ± 11%, P = 0.06) despite a lower FEV1 increase (P = 0.03) and similar SHe (P = 0.98), AX (P = 0.63), and R5-R19 decreases (P = 0.37). TcO2 and SHe changes were negatively correlated (r = −0.47, P = 0.01) after LABA, not after LAMA (r = 0.10, P = 0.65). DLNO/DLCO decreased and Vc increased after LAMA (P = 0.04; P = 0.01, respectively) but not after LABA (P = 0.53; P = 0.24). In conclusion, LAMA significantly improved tissue oxygenation in patients with COPD, while only a trend was observed with LABA. The mechanisms involved may differ between both drugs: LABA increased peripheral ventilation, whereas LAMA increased lung capillary blood volume. Should oxygenation differences persist over time, LAMA could arguably become the first therapeutic choice in COPD. NEW & NOTEWORTHY: Long-acting muscarinic antagonists (LAMAs) significantly improved tissue oxygenation in patients with COPD, while only a trend was observed with β2-agonists (LABAs). The mechanisms involved may differ between drugs: increased peripheral ventilation for LABA and likely lung capillary blood volume for LAMA. This could argue for LAMA as the first therapeutic choice in COPD. [ABSTRACT FROM AUTHOR]

Fournier's gangrene is a mortal surgical emergency characterized by rapidly spreading soft tissue necrosis between fascial planes in the perineum and genital area. The goal of treatment is early debridement of necrotic tissues to improve tissue oxygenation. In the treatment of this case, somatic oximetry monitoring, which is a non-invasive method, was applied in addition to hemodynamic monitoring to evaluate the effectiveness of fluids, antibiotics and debridements more closely. In the efficacy of the treatment, it was observed that rSO2 values correlated with other laboratory and follow-up parameters. [ABSTRACT FROM AUTHOR]

Abstract Background Hyperspectral techniques have aroused great interest in non-invasively measuring periodontal tissue hemodynamics. However, current studies mainly focused on three typical inflammation stages (healthy, gingivitis and periodontitis) and practical approaches for using optical spectroscopy for early and precisely detection of periodontal inflammation at finer disease stages have not been well studied. Methods This study provided novel spectroscopic insights into periodontitis at different stages of disease, and developed six simple but physically meaning hemodynamic spectral indices (HSIs) including four spectral absorption depths of oxyhemoglobin ( $$D_{{{\text{HbO}}_{2} }}$$ D HbO 2 ), deoxyhemoglobin ( $$D_{{{\text{Hb}}}}$$ D Hb ), total hemoglobin ( $$t{\text{Hb}}$$ t Hb ) and tissue water ( $$D_{{{\text{water}}}}$$ D water ), and two normalized difference indices of oxyhemoglobin( $$ND{\text{HbO}}_{2} I$$ N D HbO 2 I ) and deoxyhemoglobin ( $$ND{\text{Hb}}I$$ N D Hb I ) from continuum-removal spectra (400–1700 nm) of periodontal tissue collected from 47 systemically healthy subjects over different severities from healthy, gingivitis, slight, moderate to severe periodontitis for early and precision diagnostics of periodontitis. Typical statistical analyses were conducted to explore the effectiveness of the proposed HSIs. Results $$D_{{{\text{Hb}}}}$$ D Hb and $$t{\text{Hb}}$$ t Hb exerted significant increasing trends as inflammation progressed, whereas $$D_{{{\text{HbO}}_{2} }}$$ D HbO 2 exhibited significant difference (P

Introduction: Lower-body aerobic exercise with blood flow restriction (BFR) offers a unique approach for stimulating improvements in muscular function and aerobic capacity. While there are more than 40 reports documenting acute and chronic responses to lower-body aerobic exercise with BFR, responses to upper-body aerobic exercise with BFR are not clearly established. Purpose: We evaluated acute physiological and perceptual responses to arm cranking with and without BFR. Methods: Participants (N = 10) completed 4 arm cranking (6 × 2 min exercise, 1 min recovery) conditions: low-intensity at 40%VO2peak (LI), low-intensity at 40%VO2peak with BFR at 50% of arterial occlusion pressure (BFR50), low-intensity at 40%VO2peak with BFR at 70% of arterial occlusion pressure (BFR70), and high-intensity at 80%VO2peak (HI) while tissue oxygenation, cardiorespiratory, and perceptual responses were assessed. Results: During exercise, tissue saturation for BFR50 (54 ± 6%), BFR70 (55 ± 6%), and HI (54 ± 8%) decreased compared to LI (61 ± 5%, all P < 0.01) and changes in deoxyhemoglobin for BFR50 (11 ± 4), BFR70 (15 ± 6), and HI (16 ± 10) increased compared to LI (4 ± 2, all P < 0.01). During recovery intervals, tissue saturation for BFR50 and BFR70 decreased further and deoxyhemoglobin for BFR50 and BFR70 increased further (all P < 0.04). Heart rate for BFR70 and HI increased by 9 ± 9 and 50 ± 15b/min, respectively, compared to LI (both P < 0.02). BFR50 (8 ± 2, 1.0 ± 1.0) and BFR70 (10 ± 2, 2.1 ± 1.4) elicited greater arm-specific perceived exertion (6–20 scale) and pain (0–10 scale) compared to LI (7 ± 1, 0.2 ± 0.5, all P < 0.05) and pain for BFR70 did not differ from HI (1.7 ± 1.9). Conclusion: Arm cranking with BFR decreased tissue saturation and increased deoxyhemoglobin without causing excessive cardiorespiratory strain and pain. [ABSTRACT FROM AUTHOR]

Introduction: Hemorrhagic shock is characterized by derangements of the gastrointestinal microcirculation. Topical therapy with nitroglycerine or iloprost improves gastric tissue oxygenation but not regional perfusion, probably due to precapillary adrenergic innervation. Therefore, this study was designed to investigate the local effect of the parasympathomimetic carbachol alone and in combination with either nitroglycerine or iloprost on gastric and oral microcirculation during hemorrhagic shock. Methods: In a cross-over design five female foxhounds were repeatedly randomized into six experimental groups. Carbachol, or carbachol in combination with either nitroglycerine or iloprost were applied topically to the oral and gastric mucosa. Saline, nitroglycerine, or iloprost application alone served as control groups. Then, a fixed-volume hemorrhage was induced by arterial blood withdrawal followed by blood retransfusion after 1h of shock. Gastric and oral microcirculation was determined using reflectance spectrophotometry and laser Doppler flowmetry. Oral microcirculation was visualized with videomicroscopy. Statistics: 2-way-ANOVA for repeated measurements and Bonferroni post-hoc analysis (mean ± SEM; p < 0.05). Results: The induction of hemorrhage led to a decrease of gastric and oral tissue oxygenation, that was ameliorated by local carbachol and nitroglycerine application at the gastric mucosa. The sole use of local iloprost did not improve gastric tissue oxygenation but could be supplemented by local carbachol treatment. Adding carbachol to nitroglycerine did not further increase gastric tissue oxygenation. Gastric microvascular blood flow remained unchanged in all experimental groups. Oral microvascular blood flow, microvascular flow index and total vessel density decreased during shock. Local carbachol supply improved oral vessel density during shock and oral microvascular flow index in the late course of hemorrhage. Conclusion: The specific effect of shifting the autonomous balance by local carbachol treatment on microcirculatory variables varies between parts of the gastrointestinal tract. Contrary to our expectations, the improvement of gastric tissue oxygenation by local carbachol or nitroglycerine application was not related to increased microvascular perfusion. When carbachol is used in combination with local vasodilators, the additional effect on gastric tissue oxygenation depends on the specific drug combination. Therefore, modulation of tissue oxygen consumption, mitochondrial function or alterations in regional blood flow distribution should be investigated. [ABSTRACT FROM AUTHOR]

Background: Hyperspectral techniques have aroused great interest in non-invasively measuring periodontal tissue hemodynamics. However, current studies mainly focused on three typical inflammation stages (healthy, gingivitis and periodontitis) and practical approaches for using optical spectroscopy for early and precisely detection of periodontal inflammation at finer disease stages have not been well studied. Methods: This study provided novel spectroscopic insights into periodontitis at different stages of disease, and developed six simple but physically meaning hemodynamic spectral indices (HSIs) including four spectral absorption depths of oxyhemoglobin ( D HbO 2 ), deoxyhemoglobin ( D Hb ), total hemoglobin ( t Hb ) and tissue water ( D water ), and two normalized difference indices of oxyhemoglobin( N D HbO 2 I ) and deoxyhemoglobin ( N D Hb I ) from continuum-removal spectra (400–1700 nm) of periodontal tissue collected from 47 systemically healthy subjects over different severities from healthy, gingivitis, slight, moderate to severe periodontitis for early and precision diagnostics of periodontitis. Typical statistical analyses were conducted to explore the effectiveness of the proposed HSIs. Results: D Hb and t Hb exerted significant increasing trends as inflammation progressed, whereas D HbO 2 exhibited significant difference (P < 0.05) from the healthy sites only at moderate and severe periodontitis and D water presented unstable sensitives to disease severity. By contrast, N D HbO 2 I and N D Hb I showed more steadily downward trends as severity increased, and demonstrated the highest correlations with clinical gold standard parameters. Particularly, the proposed normalized HSIs ( N D HbO 2 I and N D Hb I ) yielded high correlations of − 0.49 and − 0.44 with probing depth, respectively, far outperforming results achieved by previous studies. The performances of the HSIs were also confirmed using the periodontal therapy group. Conclusions: These results indicated great potentials of combination optical spectroscopy and smart devices to non-invasively probe periodontitis at earlier stages using the simple and practical HSIs. Trial registration This study was retrospectively registered in the Chinese Clinical Trial Registry on October 24, 2021, and the clinical registration number is ChiCTR2100052306 [ABSTRACT FROM AUTHOR]

BACKGROUND: Improving neonatal abstinence syndrome (NAS) management is an important concern, and objective measures of its physiologic impact remain elusive. We sought to determine whether near-infrared spectroscopy (NIRS)-derived tissue oxygenation (rSO2) and fractional tissue oxygen extraction (FTOE) demonstrated physiologically plausible changes correlating with standard NAS scoring. METHODS: Thirty subjects (mean 39 weeks' GA and 3 127 g BW) underwent cerebral and peripheral muscle NIRS monitoring on Days of Life (DOL) Three, Five, and Seven. We examined correlations between NAS scores and FTOE and assessed the impact of non-pharmacologic swaddling and cuddling. RESULTS: No statistically significant correlations between NAS scores and FTOE were observed; however, plausible trends were demonstrated between NAS scores and cerebral measurements. Buprenorphine-exposed babies (57%) showed significantly lower FTOE when swaddled (DOL7). CONCLUSIONS: Tissue oxygenation monitoring demonstrates potential to provide objective, clinically relevant physiologic information on infants at risk for NAS. Further study is required to determine whether NIRS-derived measures could assist in individualizing NAS care. [ABSTRACT FROM AUTHOR]

Within the premature infant intestine, oxygenation and motility play key physiological roles in healthy development and disease such as necrotizing enterocolitis. To date, there are limited techniques to reliably assess these physiological functions that are also clinically feasible for critically ill infants. To address this clinical need, we hypothesized that photoacoustic imaging (PAI) can provide non-invasive assessment of intestinal tissue oxygenation and motility to characterize intestinal physiology and health. Ultrasound and photoacoustic images were acquired in 2-day and 4-day old neonatal rats. For PAI assessment of intestinal tissue oxygenation, an inspired gas challenge was performed using hypoxic, normoxic, and hyperoxic inspired oxygen (FiO2). For intestinal motility, oral administration of ICG contrast agent was used to compare control animals to an experimental model of loperamide-induced intestinal motility inhibition. PAI demonstrated progressive increases in oxygen saturation (sO2) as FiO2 increased, while the pattern of oxygen localization remained relatively consistent in both 2-day and 4-day old neonatal rats. Analysis of intraluminal ICG contrast enhanced PAI images yielded a map of the motility index in control and loperamide treated rats. From PAI analysis, loperamide significantly inhibited intestinal motility, with a 32.6% decrease in intestinal motility index scores in 4-day old rats. These data establish the feasibility and application of PAI to non-invasively and quantitatively measure intestinal tissue oxygenation and motility. This proof-of-concept study is an important first step in developing and optimizing photoacoustic imaging to provide valuable insight into intestinal health and disease to improve the care of premature infants. [Display omitted] • Intestinal tissue oxygenation and intestinal motility are important biomarkers of intestinal physiology in health and disease of premature infants. • This proof-of-concept preclinical rat study is the first to report application of photoacoustic imaging for the neonatal intestine. • Photoacoustic imaging is demonstrated as a promising non-invasive diagnostic imaging method for quantifying intestinal tissue oxygenation and intestinal motility in premature infants. [ABSTRACT FROM AUTHOR]

Background:The aim of the study was to investigate whether tissue oxygen saturation (St02) using the Near Infrared Spectroscopy method (NIRS), is a reliable and objective method for assessing the adequacy of axillary blockade and to describe the time course of StO2 changes. Materials and Methods: The study was approved by the Ethical Committee and met the Declaration of Helsinki criteria. In this prospective observational study, St02 was measured in 30 patients scheduled for elective hand surgery under axillary nevre block. Non-invasive StO2 -monitoring (InSpectra™ StO2, Hutchinson Technology Inc., Hutchinson, Minnesota, USA) was used in patients before ultrasound guided axillary brachial plexus blockade and during the first 30 minute of the blockade. Results: StO2 measurements were statistically increased in 1st, 5th, 10th, 15th, 20th, 25th, 30th minutes compared to baseline levels (p< 0.05 for all comparisons). Mean StO2 levels of the hand with axillary brachial plexus blockade were statistically increased compared the levels of the hand StO2 without blockade in 15th, 20th, 25th, 30th. minutes (p< 0.05 for all comparisons). Conclusion: There has been found a significant correlation between tissue StO2 values of two limbs using NIRS in axillary blockage operations of upper extremity. [ABSTRACT FROM AUTHOR]

IntroductionHemorrhagic shock is characterized by derangements of the gastrointestinal microcirculation. Topical therapy with nitroglycerine or iloprost improves gastric tissue oxygenation but not regional perfusion, probably due to precapillary adrenergic innervation. Therefore, this study was designed to investigate the local effect of the parasympathomimetic carbachol alone and in combination with either nitroglycerine or iloprost on gastric and oral microcirculation during hemorrhagic shock.MethodsIn a cross-over design five female foxhounds were repeatedly randomized into six experimental groups. Carbachol, or carbachol in combination with either nitroglycerine or iloprost were applied topically to the oral and gastric mucosa. Saline, nitroglycerine, or iloprost application alone served as control groups. Then, a fixed-volume hemorrhage was induced by arterial blood withdrawal followed by blood retransfusion after 1h of shock. Gastric and oral microcirculation was determined using reflectance spectrophotometry and laser Doppler flowmetry. Oral microcirculation was visualized with videomicroscopy. Statistics: 2-way-ANOVA for repeated measurements and Bonferroni post-hoc analysis (mean ± SEM; p < 0.05).ResultsThe induction of hemorrhage led to a decrease of gastric and oral tissue oxygenation, that was ameliorated by local carbachol and nitroglycerine application at the gastric mucosa. The sole use of local iloprost did not improve gastric tissue oxygenation but could be supplemented by local carbachol treatment. Adding carbachol to nitroglycerine did not further increase gastric tissue oxygenation. Gastric microvascular blood flow remained unchanged in all experimental groups. Oral microvascular blood flow, microvascular flow index and total vessel density decreased during shock. Local carbachol supply improved oral vessel density during shock and oral microvascular flow index in the late course of hemorrhage.ConclusionThe specific effect of shifting the autonomous balance by local carbachol treatment on microcirculatory variables varies between parts of the gastrointestinal tract. Contrary to our expectations, the improvement of gastric tissue oxygenation by local carbachol or nitroglycerine application was not related to increased microvascular perfusion. When carbachol is used in combination with local vasodilators, the additional effect on gastric tissue oxygenation depends on the specific drug combination. Therefore, modulation of tissue oxygen consumption, mitochondrial function or alterations in regional blood flow distribution should be investigated.

Abstract Background Near-infrared spectroscopy (NIRS) provides regional tissue oxygenation (rSO2) even in pulseless states, such as out-of-hospital cardiac arrest (OHCA). Brain rSO2 seems to be important predictor of return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR). Aim of our study was to explore feasibility for monitoring and detecting changes of skeletal muscle rSO2 during resuscitation. Methods Skeletal muscle and brain rSO2 were measured by NIRS (SenSmart Model X-100, Nonin, USA) during CPR in adult patient with OHCA. Start (basal) rSO2, maximal during CPR (maximal) and difference between maximal–minimal rSO2 (delta-rSO2), were recorded. Patients were divided into ROSC and NO-ROSC group. Results 20 patients [age: 66.0ys (60.5–79.5), 65% male] with OHCA [50% witnessed, 70% BLS, time to ALS 13.5 min (11.0–19.0)] were finally analyzed. ROSC was confirmed in 5 (25%) patients. Basal and maximal skeletal muscle rSO2 were higher in ROSC compared to NO-ROSC group [49.0% (39.7–53.7) vs. 15.0% (12.0–25.2), P = 0.006; 76.0% (52.7–80.5) vs. 34.0% (18.0–49.5), P = 0.005, respectively]. There was non-linear cubic relationship between time of collapse and basal skeletal muscle rSO2 in witnessed OHCA and without BLS (F-ratio = 9.7713, P = 0.0261). There was correlation between maximal skeletal muscle and brain rSO2 (n = 18, rho: 0.578, P = 0.0121). Conclusions Recording of skeletal muscle rSO2 during CPR in patients with OHCA is feasible. Basal and maximal skeletal muscle rSO2 were higher in ROSC compared to NO-ROSC group. Clinical trial registration number ClinicalTrials.gov, NCT04058925, registered on: 16th August 2019. URL of trial registry record: https://www.clinicaltrials.gov/ct2/show/NCT04058925?titles=Tissue+Oxygenation+During+Cardiopulmonary+Resuscitation+as+a+Predictor+of+Return+of+Spontaneous+Circulation&draw=2&rank=1 .

Background: Near-infrared spectroscopy (NIRS) provides regional tissue oxygenation (rSO2) even in pulseless states, such as out-of-hospital cardiac arrest (OHCA). Brain rSO2 seems to be important predictor of return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR). Aim of our study was to explore feasibility for monitoring and detecting changes of skeletal muscle rSO2 during resuscitation. Methods: Skeletal muscle and brain rSO2 were measured by NIRS (SenSmart Model X-100, Nonin, USA) during CPR in adult patient with OHCA. Start (basal) rSO2, maximal during CPR (maximal) and difference between maximal–minimal rSO2 (delta-rSO2), were recorded. Patients were divided into ROSC and NO-ROSC group. Results: 20 patients [age: 66.0ys (60.5–79.5), 65% male] with OHCA [50% witnessed, 70% BLS, time to ALS 13.5 min (11.0–19.0)] were finally analyzed. ROSC was confirmed in 5 (25%) patients. Basal and maximal skeletal muscle rSO2 were higher in ROSC compared to NO-ROSC group [49.0% (39.7–53.7) vs. 15.0% (12.0–25.2), P = 0.006; 76.0% (52.7–80.5) vs. 34.0% (18.0–49.5), P = 0.005, respectively]. There was non-linear cubic relationship between time of collapse and basal skeletal muscle rSO2 in witnessed OHCA and without BLS (F-ratio = 9.7713, P = 0.0261). There was correlation between maximal skeletal muscle and brain rSO2 (n = 18, rho: 0.578, P = 0.0121). Conclusions: Recording of skeletal muscle rSO2 during CPR in patients with OHCA is feasible. Basal and maximal skeletal muscle rSO2 were higher in ROSC compared to NO-ROSC group. Clinical trial registration number ClinicalTrials.gov, NCT04058925, registered on: 16th August 2019. URL of trial registry record: https://www.clinicaltrials.gov/ct2/show/NCT04058925?titles=Tissue+Oxygenation+During+Cardiopulmonary+Resuscitation+as+a+Predictor+of+Return+of+Spontaneous+Circulation&draw=2&rank=1. [ABSTRACT FROM AUTHOR]

Several spinal motor output and essential rhythmic behaviors are controlled by supraspinal structures, although their contribution to neuronal networks for respiration and locomotion at birth still requires better characterization. As preparations of isolated brainstem and spinal networks only focus on local circuitry, we introduced the in vitro central nervous system (CNS) from neonatal rodents to simultaneously record a stable respiratory rhythm from both cervical and lumbar ventral roots (VRs). Electrical pulses supplied to multiple sites of brainstem evoked distinct VR responses with staggered onset in the rostro-caudal direction. Stimulation of ventrolateral medulla (VLM) resulted in higher events from homolateral VRs. Stimulating a lumbar dorsal root (DR) elicited responses even from cervical VRs, albeit small and delayed, confirming functional ascending pathways. Oximetric assessments detected optimal oxygen levels on brainstem and cortical surfaces, and histological analysis of internal brain structures indicated preserved neuron viability without astrogliosis. Serial ablations showed precollicular decerebration reducing respiratory burst duration and frequency and diminishing the area of lumbar DR and VR potentials elicited by DR stimulation, while pontobulbar transection increased the frequency and duration of respiratory bursts. Keeping legs attached allows for expressing a respiratory rhythm during hindlimb stimulation. Trains of pulses evoked episodes of fictive locomotion (FL) when delivered to VLM or to a DR, the latter with a slightly better FL than in isolated cords. In summary, suprapontine centers regulate spontaneous respiratory rhythms, as well as electrically evoked reflexes and spinal network activity. The current approach contributes to clarifying modulatory brain influences on the brainstem and spinal microcircuits during development. Novel preparation of the entire isolated CNS from newborn rats unveils suprapontine modulation on brainstem and spinal networks. Preparation views (A) with and without legs attached (B). Successful fictive respiration occurs with fast dissection from P0-P2 rats (C). Decerebration speeds up respiratory rhythm (D) and reduces spinal reflexes derived from both ventral and dorsal lumbar roots (E). [ABSTRACT FROM AUTHOR]

Quantifying relationships between cerebral blood flow (CBF), mitochondrial function (cytochrome c oxidase oxidation state), and metabolic rate of oxygen (CMRO2) could provide useful insight into normal neurovascular coupling, as well as regulation of oxidative metabolism in neurological disorders. This paper uses a multimodal NIRS-MRI method to quantify these parameters in rodent brain and, in so doing, provides novel information on the regulation of oxygen metabolism by stimulating with hypercapnia or variations in oxygenation. Under hypercapnia, although oxygenation, oxidation state, and CBF increased, there was no increase in CMRO2. Also, there was no correlation between CBF and CCO oxidation state. Conversely, changing oxygenation resulted in a strong correlation between the oxidation of CCO and CBF. This proves that the association between CBF and the redox state of CCO is not fixed and depends on the type of perturbation. Having a means to measure CBF and CCO oxidation state simultaneously will help understanding their contribution to intact neurovascular coupling and detecting abnormal cellular oxygen metabolism in many neurological disorders. [ABSTRACT FROM AUTHOR]

The effects of concurrent optical and magnetic stimulation (COMS) therapy on wound-healing-related parameters, such as tissue oxygenation and water index, were analyzed by hyperspectral imaging: an exploratory case series. Background: Oedema and inadequate perfusion have been identified as key factors in delayed wound healing and have been linked to reduced mitochondrial respiration. Targeting mitochondrial dysfunction is a promising approach in the treatment of therapy refractory wounds. This sub-study aimed to investigate the effects of concurrent optical and magnetic stimulation (COMS) on oedema and perfusion through measuring tissue oxygenation and water index, using hyperspectral imaging. Patients and methods: In a multi-center, prospective, comparative clinical trial, eleven patients with chronic leg and foot ulcers were treated with COMS additively to Standard of Care (SOC). Hyperspectral images were collected during patient visits before and after treatment to assess short- and long-term hemodynamic and immunomodulatory effects through changes in tissue oxygenation and water index. Results: The average time for wound onset in the eleven patients analyzed was 183 days, with 64% of them being considered unresponsive to SOC. At week 12, the rate of near-complete and complete wound closure was 64% and 45%, respectively. COMS therapy with SOC resulted in an increased short-term tissue oxygenation over the 8-week treatment phase, with oxygen levels decreasing in-between patient visits. The study further found a decrease in tissue water content after the therapy, with a general accumulation of water levels in-between patient visits. This study's long-term analysis was hindered by the lack of absolute values in hyperspectral imaging and the dynamic nature of patient parameters during visits, resulting in high interpatient and intervisit variability. Conclusions: This study showed that COMS therapy as an adjunct to SOC had a positive short-term effect on inflammation and tissue oxygenation in chronic wounds of various etiologies. These results further supported the body of evidence for safety and effectiveness of COMS therapy as a treatment option, especially for stagnant wounds that tended to stay in the inflammatory phase and required efficient phase transition towards healing. [ABSTRACT FROM AUTHOR]

According to Fick's principle, the total uptake of (or release of) a substance by tissues is the product of blood flow and the difference between the arterial and the venous concentration of the substance. Therefore, the mixed or central venous minus arterial CO2 content difference depends on cardiac output (CO). Assuming a linear relationship between CO2 content and partial pressure, central or mixed venous minus arterial PCO2 differences (Pcv-aCO2 and Pmv-aCO2) are directly related to CO. Nevertheless, this relationship is affected by alterations in the CO2Hb dissociation curve induced by metabolic acidosis, hemodilution, the Haldane effect, and changes in CO2 production (VCO2). In addition, Pcv-aCO2 and Pmv-aCO2 are not interchangeable. Despite these confounders, CO is a main determinant of Pcv-aCO2. Since in a study performed in septic shock patients, Pmv-aCO2 was correlated with changes in sublingual microcirculation but not with those in CO, it has been proposed as a monitor for microcirculation. The respiratory quotient (RQ)—RQ = VCO2/O2 consumption—sharply increases in anaerobic situations induced by exercise or critical reductions in O2 transport. This results from anaerobic VCO2 secondary to bicarbonate buffering of anaerobically generated protons. The measurement of RQ requires expired gas analysis by a metabolic cart, which is not usually available. Thus, some studies have suggested that the ratio of Pcv-aCO2 to arterial minus central venous O2 content (Pcv-aCO2/Ca-cvO2) might be a surrogate for RQ and tissue oxygenation. In this review, we analyze the physiologic determinants of Pcv-aCO2 and Pcv-aCO2/Ca-cvO2 and their potential usefulness and limitations for the monitoring of critically ill patients. We discuss compelling evidence showing that they are misleading surrogates for tissue perfusion and oxygenation, mainly because they are systemic variables that fail to track regional changes. In addition, they are strongly dependent on changes in the CO2Hb dissociation curve, regardless of changes in systemic and microvascular perfusion and oxygenation. [ABSTRACT FROM AUTHOR]

Introduction: Current oxygen monitoring by pulse oximetry has limitations and cannot provide estimates of the oxygen content in the microvasculature, where oxygen is used. Resonance Raman spectroscopy (RRS) provides noninvasive microvascular oxygen measurement. The objectives of this study were to (i) measure the correlation between preductal RRS microvascular oxygen saturations (RRS-StO2) and central venous oxygen saturation (SCVO2), (ii) develop normative data for RRS-StO2 measurements in healthy preterm infants, and (iii) determine the effect of blood transfusion on RRS-StO2. Methods: Thirty-three buccal and thenar RRS-StO2 measurements were performed in 26 subjects to correlate RRS-StO2 with SCVO2. Thirty-one measurements were performed in 28 subjects to develop normative RRS-StO2 values, and eight subjects were enrolled in the transfusion group to assess changes in RRS-StO2 with blood transfusion. Results: There were good correlations for buccal (r = 0.692) and thenar (r = 0.768) RRS-StO2 versus SCVO2. The median RRS-StO2 in healthy subjects was 76% (IQR 68.7–80.8). There was a significant increase of 7.8 ± 4.6% in the thenar RRS-StO2 after blood transfusion. Conclusions: RRS appears to be a safe and noninvasive means of monitoring microvascular oxygenation. Thenar RRS-StO2 measurements are more feasible and practical to use than buccal. In healthy preterm infants, the median RRS-StO2 was calculated based on measurements across various gestational age and gender. More studies evaluating the effects of gestational age of RRS-StO2 in various critical clinical settings are needed to confirm the findings. [ABSTRACT FROM AUTHOR]

Oxygen is essential for cellular respiration and energy production. Tissue oxygenation refers to delivering oxygen to cells throughout the body. Microcirculation brings blood through small sanguine vessels to maintain the cells' supply of nutrients and oxygen. Optimal tissue oxygenation and microcirculation are essential for maintaining healthy tissue. Conversely, poor oxygenation can cause tissue damage, impair wound healing, and increase infection risk. Several factors can affect tissue oxygenation and microcirculation, including age, lifestyle factors (such as smoking and stress), and underlying medical conditions (such as diabetes and high blood pressure). To improve tissue oxygenation and microcirculation, individuals can engage in healthy lifestyle habits such as regular exercise, healthy eating, stress management, and avoiding smoking. Tissue oxygenation can also be looked therapeutic, given that topical and cosmetic treatments such as massage, pelotherapy, hydrotherapy, moisturizers, and certain skin care products can help promote healthy microcirculation at the somatic level. In the scientific literature, the focus is on hypoxia rather than tissue oxygenation. This article proposes a paradigm shift and emphasizes the homeostatic importance of microcirculation and tissue oxygenation in pathophysiological and therapeutic circumstances. The systematic review of the data from the last 2 years (2021-2022) and the meta-analysis performed on tissue oxygenation will contribute to the practical approach to the pathology circumscribed to tissue oxygenation. [ABSTRACT FROM AUTHOR]

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 50 mmHg 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 50 mmHg 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. [ABSTRACT FROM AUTHOR]

Purpose: O3® Regional Oximetry (Masimo Corporation, California, USA) is validated for cerebral oximetry. We aimed to assess agreement of somatic and renal near-infrared spectroscopy with reference blood samples. Methods: O3 sensors were placed bilaterally on the quadriceps and flank of 26 healthy volunteers. A stepped, controlled hypoxia sequence was performed by adding a mixture of nitrogen and room air to the breathing circuit. O3-derived oxygen saturation values were obtained at baseline and at six decremental saturation levels (5% steps). Blood samples (radial artery, iliac vein (somatic reference) and renal vein) were obtained at each step. Reference values were calculated as: 0.7 × venous saturation + 0.3 × arterial saturation. The agreement between O3-derived values with blood reference values was assessed by calculating root-mean-square error accuracy and Bland-Altman plots. Results: The root-mean-square error accuracy was 6.0% between quadriceps oxygen saturation and somatic reference values. The mean bias was 0.8%, with limits of agreement from -7.7 to 9.3%. These were 5.1% and 0.6% (-8.3 to 9.5%) for flank oxygen saturation and somatic reference values, respectively, and 7.7% and -4.9% (-15.0 to 5.2%) for flank oxygen saturation and renal reference values. The kidney depth was 3.1 ± 0.9 cm below the skin. Conclusion: O3 regional oximetry can be used on the quadriceps and flank to monitor somatic saturation, yet has a saturation-level dependent bias. O3-derived values obtained at the flank underestimated renal reference values. Additionally, it is unlikely that the flank sensors did directly measure renal tissue. Trial registration: Clinicaltrials.gov (NCT04584788): registered October 6th, 2020. [ABSTRACT FROM AUTHOR]

Abstract Purpose Carbon dioxide (CO2) increases cerebral perfusion. The effect of CO2 on apnea tolerance, such as after anesthesia induction, is unknown. This study aimed to assess if cerebral apnea tolerance can be improved in obese patients under general anesthesia when comparing O2/Air (95%O2) to O2/CO2 (95%O2/5%CO2). Methods In this single-center, single-blinded, randomized crossover trial, 30 patients 18–65 years, with body mass index > 35 kg/m2, requiring general anesthesia for bariatric surgery, underwent two apneas that were preceded by ventilation with either O2/Air or O2/CO2 in random order. After anesthesia induction, intubation, and ventilation with O2/Air or O2/CO2 for 10 min, apnea was performed until the cerebral tissue oxygenation index (TOI) dropped by a relative 20% from baseline (primary endpoint) or oxygen saturation (SpO2) reached 80% (safety abortion criterion). The intervention was then repeated with the second substance. Results The safety criterion was reached in all patients before cerebral TOI decreased by 20%. The time until SpO2 dropped to 80% was similar in the two groups (+ 6 s with O2/CO2, 95%CI -7 to 19 s, p = 0.37). Cerebral TOI and PaO2 were higher after O2/CO2 (+ 1.5%; 95%CI: from 0.3 to 2.6; p = 0.02 and + 0.6 kPa; 95%CI: 0.1 to 1.1; p = 0.02). Conclusion O2/CO2 improves cerebral TOI and PaO2 in anesthetized bariatric patients. Better apnea tolerance could not be confirmed.

The increasing prevalence of vascular diseases encourages the development of minimally invasive approaches to assess tissue perfusion. A significant challenge facing current state-of-the-art methods is their validation against clinical data. In this study, we introduce an open-source database designed to evaluate tissue perfusion during the application of an occlusion protocol. The database comprises sequences of multi-spectral images (visible and near-infrared region) from the subjects’ predominant hand and their photoplethysmography data for validation. Our study recruited 45 healthy participants, including 21 females, with an age range between 18–24 years old (standard deviation equal to 1.73). The database was evaluated using two methods for estimating skin perfusion parameters based on multi-spectral images: a Kubelka-Munk model, and a linear regression. Meanwhile, for validation purposes, the changes in oxygenated and deoxygenated hemoglobin were evaluated by photoplethysmography data as baseline perfusion parameters. The Pearson correlation between plethysmography-based perfusion parameters and those extracted from multi-spectral images was evaluated in all cases as a validation metric. Our findings demonstrated a strong Pearson correlation ( $\rho >0.7$ ) between changes in oxygenated and deoxygenated hemoglobin and multi-spectral based perfusion parameters, suggesting that the database is useful for further research related to in-vivo perfusion assessment. The primary objective of this database is to provide open-source data from a controlled occlusion protocol to evaluate new approaches based on multi-spectral images in the visible and near-infrared regions. In addition, the validation by photoplethysmography data facilitates the development and assessment of innovative tissue perfusion estimation techniques.

Atherosclerosis is a complex pathological condition marked by the accumulation of lipids in the arterial wall, leading to the development of plaques that can eventually rupture and cause thrombotic events. In recent years, hydrogen sulfide (H2S) has emerged as a key mediator of cardiovascular homeostasis, with potential therapeutic applications in atherosclerosis. This systematic review highlights the importance of understanding the complex interplay between H2S, oxygen homeostasis, and atherosclerosis and suggests that targeting H2S signaling pathways may offer new avenues for treating and preventing this condition. Oxygen homeostasis is a critical aspect of cardiovascular health, and disruption of this balance can contribute to the development and progression of atherosclerosis. Recent studies have demonstrated that H2S plays an important role in maintaining oxygen homeostasis by regulating the function of oxygen-sensing enzymes and transcription factors in vascular cells. H2S has been shown to modulate endothelial nitric oxide synthase (eNOS) activity, which plays a key role in regulating vascular tone and oxygen delivery to tissues. The comprehensive analysis of the current understanding of H2S in atherosclerosis can pave the way for future research and the development of new therapeutic strategies for this debilitating condition. PROSPERO ID: 417150. [ABSTRACT FROM AUTHOR]

This paper aimed to examine the acute effect of low-load (LL) exercise with blood-flow restriction (LL-BFR) on microvascular oxygenation and muscle excitability of the vastus medialis (VM) and vastus lateralis (VL) muscles during a single bout of unilateral knee extension exercise performed to task failure. Seventeen healthy recreationally resistance-trained males were enrolled in a within-group randomized cross-over study design. Participants performed one set of unilateral knee extensions at 20% of one-repetition maximum (1RM) to task failure, using a LL-BFR or LL free-flow (LL-FF) protocol in a randomized order on separate days. Changes in microvascular oxygenation and muscle excitability in VL and VM were assessed using near-infrared spectroscopy (NIRS) and surface electromyography (sEMG), respectively. Pain measures were collected using the visual analog scale (VAS) before and following set completion. Within- and between- protocol comparisons were performed at multiple time points of set completion for each muscle. During LL-BFR, participants performed 43% fewer repetitions and reported feeling more pain compared to LL-FF (p<0.05). Normalized to time to task failure, LL-BFR and LL-FF generally demonstrated similar progression in microvascular oxygenation and muscle excitability during exercise to task failure. The present results demonstrate that LL-BFR accelerates time to task failure, compared with LL-FF, resulting in a lower dose of mechanical work to elicit similar levels of oxygenation, blood-pooling, and muscle excitability. LL-BFR may be preferable to LL-FF in clinical settings where high workloads are contraindicated, although increased pain experienced during BFR may limit its application. Highlights Compared to free flow (FF), neuromuscular fatigue mechanisms are accelerated during blood flow restricted (BFR) training. This can be observed as changes in microvascular oxygenation and muscle excitability occurring at a ∼43% faster mean rate during BFR compared to FF. BFR exercise seems to elicit the same level of neuromuscular fatigue as FF training within a shorter timeframe. This reduces total joint load and may be especially helpful in cases where high training volumes may be contraindicated (e.g. recovering from a sports injury or orthopedic surgery). [ABSTRACT FROM AUTHOR]

Compartment syndrome (CS) continues to be a legitimate orthopedic emergency as it leads to thousands of amputations and permanent nerve and tissue damage to undiagnosed patients for more than eight hours. In CS, intracompartmental pressure is elevated, causing reduced blood flow inside the limb compartments. An erroneous diagnosis may result in unnecessary fasciotomies, the only treatment for this condition. This review examines the previous and current diagnostic and therapeutic practices for compartment syndrome. It also performs a comparative analysis of each diagnostic technique and its foresights. Currently, most clinicians rely on a physical examination of the patient to diagnose CS. The primary reason for the physical examination is the lack of a gold-standard device. The invasive intracompartmental pressure (ICP) measurement technique is still the most commonly used. On the other hand, many noninvasive approaches have the potential to be used as diagnostic tools; however, more research is needed before they can be accepted as standard clinical approaches. [ABSTRACT FROM AUTHOR]

Simple Summary: Ischemic preconditioning (IPC) is a protective maneuver that alternates short periods of occlusion and reperfusion of tissue blood flow. Nineteen subjects were enrolled in one of the two groups, IPC (3 × 5/5 min right arm ischemia/reperfusion; cuff inflations 250 mmHg) and SHAM (3 × 5/5 min pseudo ischemia/reperfusion; 20 mmHg). The subjects performed a fatiguing contraction protocol before and 30 min after the IPC treatment. Results suggest that IPC may delay fatigue onset by reducing muscle oxygen consumption. The decrease in tissue oxygenation and the increase in deoxygenated hemoglobin were significantly reduced post- vs. pre-IPC (p < 0.05), but not post- vs. pre-SHAM. IPC delays the onset of fatigue, probably due to improved metabolic efficiency of muscles. Ischemic preconditioning (IPC) is a non-invasive protective maneuver that alternates short periods of occlusion and reperfusion of tissue blood flow. Given the heterogeneity in the magnitude and frequency of IPC-induced improvements in physical performance, here we aimed to investigate, in a well-controlled experimental set-up, the local effects of IPC in exposed muscles in terms of tissue oxygenation and muscle fatigue. Nineteen subjects were enrolled in one of the two groups, IPC (3 × 5/5 min right arm ischemia/reperfusion; cuff inflations 250 mmHg) and SHAM (3 × 5/5 min pseudo ischemia/reperfusion; 20 mmHg). The subjects performed a fatiguing contraction protocol before and 30 min after the IPC treatment, consisting of unilateral intermittent isometric elbow flexions (3 s ON/OFF, 80% of maximal voluntary contraction) until exhaustion. While muscle strength did not differ between groups, post- vs. pre-treatment endurance was significantly reduced in the SHAM group (4.1 ± 1.9 vs. 6.4 ± 3.1 repetitions until exhaustion, p < 0.05) but maintained in IPC (7.3 ± 2.0 vs. 7.1 ± 4.3, n.s.). The decrease in tissue oxygenation and the increase in deoxygenated hemoglobin were significantly reduced post- vs. pre-IPC (p < 0.05), but not post- vs. pre-SHAM. The results suggest that IPC delays the onset of fatigue likely through improved metabolic efficiency of muscles. [ABSTRACT FROM AUTHOR]

Acute ischemic stroke results in an ischemic core surrounded by a tissue at risk, named the penumbra, which is potentially salvageable. One way to differentiate the tissues is to measure the hypoxia status. The purpose of the current study is to correlate the abnormal brain tissue volume derived from magnetic resonance‐based imaging of brain oxygen saturation (StO2‐MRI) to the fluorine‐18 fluoromisonidazole ([18F]FMISO) positron emission tomography (PET) volume for hypoxia imaging validation, and to analyze the ability of StO2‐MRI to depict the different hypoxic tissue types in the acute phase of stroke. In a pertinent model of stroke in the rat, the volume of tissue with decreased StO2‐MRI signal and that with increased uptake of [18F]FMISO were equivalent and correlated (r = 0.706; p = 0.015). The values of StO2 in the tissue at risk were significantly greater than those quantified in the core of the lesion, and were less than those for healthy tissue (52.3% ± 2.0%; 43.3% ± 1.9%, and 67.9 ± 1.4%, respectively). A threshold value for StO2 of ≈60% as the cut‐off for the identification of the tissue at risk was calculated. Tissue volumes with reduced StO2‐MRI correlated with the final lesion (r = 0.964, p < 0.0001). The findings show that the StO2‐MRI approach is sensitive for the detection of hypoxia and for the prediction of the final lesion after stroke. Once validated in acute clinical settings, this approach might be used to enhance the stratification of patients for potential therapeutic interventions. [ABSTRACT FROM AUTHOR]

ObjectivesTo determine the correlation and agreement between the SenSmart™ and the INVOS™ devices of neonatal cerebral regional oxygen saturation (CrSO2) measurements using neonatal sensors. The secondary objective was to develop a regression model that predicts CrSO2-INVOS values using CrSO2-SenSmart indices and determine whether the values between the devices are interchangeable.MethodsA prospective, cross-sectional study was conducted in infants during the first 4 weeks of life. Simultaneous, bilateral CrSO2 was measured using the SenSmart™X100 (CrSO2-SenSmart) or INVOS™ 5100C (CrSO2-INVOS) device in each frontoparietal area for 2 h. Five-minute CrSO2 values were extracted for analysis.ResultsThirty infants were recruited with 720 pairwise measurements and 26 (84%) were evaluated in the first week of life. Mean gestational age of the preterm and term infants was [30.9 ± 2.8 (n = 14) and 38.8 ± 1.1 (n = 16)] weeks, respectively. Overall CrSO2- was 77.08 ± 9.70% and 71.45 ± 12.74% for the SenSmart and INVOS, respectively (p

Purpose: Carbon dioxide (CO2) increases cerebral perfusion. The effect of CO2 on apnea tolerance, such as after anesthesia induction, is unknown. This study aimed to assess if cerebral apnea tolerance can be improved in obese patients under general anesthesia when comparing O2/Air (95%O2) to O2/CO2 (95%O2/5%CO2). Methods: In this single-center, single-blinded, randomized crossover trial, 30 patients 18–65 years, with body mass index > 35 kg/m2, requiring general anesthesia for bariatric surgery, underwent two apneas that were preceded by ventilation with either O2/Air or O2/CO2 in random order. After anesthesia induction, intubation, and ventilation with O2/Air or O2/CO2 for 10 min, apnea was performed until the cerebral tissue oxygenation index (TOI) dropped by a relative 20% from baseline (primary endpoint) or oxygen saturation (SpO2) reached 80% (safety abortion criterion). The intervention was then repeated with the second substance. Results: The safety criterion was reached in all patients before cerebral TOI decreased by 20%. The time until SpO2 dropped to 80% was similar in the two groups (+ 6 s with O2/CO2, 95%CI -7 to 19 s, p = 0.37). Cerebral TOI and PaO2 were higher after O2/CO2 (+ 1.5%; 95%CI: from 0.3 to 2.6; p = 0.02 and + 0.6 kPa; 95%CI: 0.1 to 1.1; p = 0.02). Conclusion: O2/CO2 improves cerebral TOI and PaO2 in anesthetized bariatric patients. Better apnea tolerance could not be confirmed. [ABSTRACT FROM AUTHOR]

Previous studies have shown tart cherry (TC) to improve exercise performance in normoxia. The effect of TC on hypoxic exercise performance is unknown. This study investigated the effects of 5 days of tart cherry (TC) or placebo (PL) supplementation on hypoxic exercise performance. Thirteen healthy participants completed an incremental cycle exercise test to exhaustion (TTE) under two conditions: (i) hypoxia (13% O2) with PL and (ii) hypoxia with TC (200 mg anthocyanin per day for 4 days and 100 mg on day 5). Pulmonary gas exchange variables, peripheral arterial oxygen saturation (SpO2), deoxygenated hemoglobin (HHb), and tissue oxygen saturation (StO2) assessed by near-infrared spectroscopy in the vastus lateralis muscle were measured at rest and during exercise. Urinary 8-hydro-2′ deoxyguanosine (8-OHdG) excretion was evaluated pre-exercise and 1 and 5 h post-exercise. The TTE after TC (940 ± 84 s, mean ± standard deviation) was longer than after PL (912 ± 63 s, p < 0.05). During submaximal hypoxic exercise, HHb was lower and StO2 and SpO2 were higher after TC than PL. Moreover, a significant interaction (supplements × time) in urinary 8-OHdG excretion was found (p < 0.05), whereby 1 h post-exercise increases in urinary 8-OHdG excretion tended to be attenuated after TC. These findings indicate that short-term dietary TC supplementation improved hypoxic exercise tolerance, perhaps due to lower HHb and higher StO2 in the working muscles during submaximal exercise. [ABSTRACT FROM AUTHOR]