Tissue Oxygen Saturation Research Articles

Feasibility and safety of weaning premature infants from nasal continuous positive airway pressure to high-flow nasal cannula: a prospective observational case study.

Nasal continuous positive airway pressure (NCPAP) is widely used for premature infants with respiratory distress syndrome (RDS). A high-flow nasal cannula (HFNC) provides positive end-expiratory pressure using high-flow oxygen; however, the variability in distending pressure is a primary concern. This study evaluated the feasibility and safety of a newly designed protocol for NCPAP weaning with cyclic HFNC use for premature infants. Premature infants with RDS using NCPAP support who were ready for weaning were enrolled. The weaning protocol used cyclic NCPAP with HFNC every 3h for 3 days in the neonatal intensive care unit. The heart rate (HR), respiratory rate (RR), pulse oximetry (SpO2), transcutaneous carbon dioxide (PtcCO2), and cerebral tissue oxygen saturation (StO2) at the end of NCPAP with HFNC support were recorded once daily for 3 days. From June 2019 to April 2021, 46 premature infants (27 male, 19 female) were enrolled. The mean gestational age and birth body weight were 28.7 ± 2.6 weeks and 1181 ± 354g, respectively. No statistically significant differences in the HR, RR, SpO2, and cerebral StO2 during NCPAP weaning with HFNC were observed. However, the mean PtcCO2 with NCPAP was statistically significantly lower than that with HFNC (46.9 ± 6.0 mmHg vs. 47.9 ± 6.4 mmHg, P = 0.02). The feasibility and safety of the NCPAP weaning protocol with cyclic HFNC for premature infants are acceptable in this preliminary study. Due to the limited number of participants, further studies are required for more comprehensive analysis. This prospective observational case study was approved by the Human Experiment and Ethics Committee of our hospital (approval number: KMUHIRB-SV(I)-20180059; approval date: January 11, 2019).

The effect of vo2max on muscle oxygen saturation (SMO2) in University Badminton Athletes

Muscle oxygen saturation (SmO2) is an additional physiological parameter that helps identify the transition from aerobic to anaerobic workload. Additionally, it can be used to predict performance by calculating Vo2 and energy expenditure. Muscle oxygen saturation (SmO2) is a measure of oxygen saturation in muscle tissue that can be used to evaluate metabolic zones, training intensity, and athlete performance. An athlete's muscle oxygen saturation (SMO2) is a measure of how well their muscles use oxygen, which is important for evaluating performance and creating training programs. This research is a week-long experimental study with a one-shot case study design, research intends to look at the effect of Vo2Max on muscle oxygen saturation (SMO2) in university badminton athletes. The subjects of this research are student athletes who actively practice badminton. There were 6 respondents who were willing to be research subjects and had met the specified criteria, namely actively exercising three times a week and being in good health. Then the author took data on athletes who had the highest and lowest Vo2Max to analyze SMO2 optimization, which was the focus of this research. The results of the analysis show that there is a significant influence between Vo2max and SMO2 optimization; this can be seen by the difference through the t test with a sig (2-tailed) value of 0.000 < 0.05. Another finding is that athletes with higher Vo2max show better SMO2 recovery results. better than athletes with low Vo2max; in this study, athletes with higher Vo2max showed a 37% increase in SMO2 over two minutes, while athletes with lower Vo2max showed a 21% increase. This is an interesting finding for coaches and athletes regarding the importance of Vo2 max capacity in optimizing SMO2.

Cerebral near-infrared spectroscopy guided neonatal intensive care management for the preterm infant.

Infants requiring admission to the neonatal intensive care unit (NICU) are particularly vulnerable to developing brain injury. The severity of the underlying clinical conditions and the complexity of care call for continuous, cot-side, non-invasive monitoring tools. Near-infrared spectroscopy (NIRS) measures the regional tissue oxygen saturation of hemoglobin (rStO2) and provides continuous information on the net-result of several factors. Cerebral rStO2 correlates with echocardiography-derived measures of blood flow. Cerebral fractional tissue oxygen extraction provides information on the balance between oxygen supply and demand and can be continuously derived from the combined use of cerebral rStO2 and arterial oxygen saturation. Information on cerebral blood flow autoregulatory capacity can be obtained from combining cerebral rStO2 and invasive blood pressure monitoring by appropriate software. Cerebral rStO2 provides real-time, end-organ information on perfusion-oxygenation, and when interpreted in the clinical context based on pathophysiological principles may be used as a help to guide interventions in the NICU. In this review we will discuss how to optimize NIRS monitoring for application in the NICU, with a particular focus on the preterm infant. IMPACT: Near-infrared spectroscopy (NIRS) provides cot-side, real-time information on blood and oxygen supply to the brain. Therefore, it is a valuable tool to better understand the pathophysiology underlaying disease processes. Current evidence suggests that NIRS-guided treatment in extremely preterm infants during transitional circulation does not improve clinical outcomes. Specific training is needed to maximize potential performance. Pathophysiological interpretation of cerebral NIRS data in the given clinical context may help in decision-making. Appropriate use of this monitoring technique, interpreted concurrently with other routine parameters, is a potential clinical tool to guide interventions in the NICU setting.

Assessment of Microcirculatory Dysfunction by Measuring Subcutaneous Tissue Oxygen Saturation Using Near-Infrared Spectroscopy in Patients with Circulatory Failure.

Patients with circulatory failure have high mortality rates and require prompt assessment of microcirculation. Despite the improvement in hemodynamic parameters, microcirculatory dysfunction persists. We measured subcutaneous regional tissue oxygen saturation (rSO2) with near-infrared spectroscopy (NIRS), which can assess microcirculation in patients with circulatory failure. A finger-worn oximeter with NIRS measured rSO2 in the forehead, thenar eminence, thumb, and knees. First, the rSO2 was measured in healthy adult volunteers (n = 10). Circulatory failure was defined as a systolic blood pressure ≤ 90 mmHg and lactate ≥ 2 mmol/L. The study included 35 patients without circulatory failure and SOFA score of 0 at ICU admission and 38 patients with circulatory failure at ICU admission. Both groups included a single-center prospective study of patients who were transported to the ICU of the Nihon University Hospital. The rSO2 was measured only on ICU admission in the non-circulatory failure group and later in the circulatory failure group. In the volunteer group, rSO2 at each site was approximately 58%. The rSO2 was significantly lower in the circulatory failure group than in the non-circulatory failure group (knee, p < 0.01). In the circulatory failure group, knee rSO2 showed a significant negative correlation with SOFA score (Day 0, ρ = -0.37, p = 0.02; Day 1, ρ = -0.53, p < 0.01; Day 2, ρ = -0.60, p < 0.01). Subcutaneous knee rSO2 was associated with SOFA score and was considered an indicator of microcirculatory dysfunction and organ damage.

Multimodal Photoacoustic/Elastography Imaging for the Detection of Acute Radiation Dermatitis in Breast Radiation Therapy

Purpose: This study evaluates whether photoacoustic (PA), sound touch elastography (STE), and viscoelasticity (VE) can distinguish between normal and abnormal post-radiotherapy breast skin and compare these methods with RTOG criteria at a 20 Gy threshold. Methods: Patients meeting inclusion and exclusion criteria underwent PA, STE, and VE on the same day. Collected data included radiation dose, molecular type, RTOG, Fitzpatrick skin type, pathology, neoadjuvant chemotherapy status, TNM classification, surgical procedures, primary breast cancer location, BMI, and age. A sample of 41 patients was determined using a two-sample t-test. Statistical tools like T-tests, variance analysis, rank sum tests, and chi-square tests, along with random forest analysis and ROC curves, were used to evaluate the radiation dose effects. Results: Data from 66 patients showed significant differences in parameters such as dermis and subcutaneous tissue oxygen saturation, dermal thickness, and skin elasticity (p-values < 0.05). However, minimum values of oxygen saturation and some photoacoustic measures were not significantly different. Notably, at a 20 Gy radiation threshold, significant variations in oxygen saturation, abnormal dermal thickness, and skin STE and VE were observed, proving more accurate than RTOG grading. Conclusion: The study confirms the effectiveness of PA and elastography imaging in differentiating normal from abnormal breast tissue and assessing radiation-induced changes, highlighting the potential of these imaging techniques.

Examining the Hydration Status and Pulse/Oxygen Saturation of Underwater Hockey Players

Objectives: This study was planned to determine the hydration status and tissue oxygen saturation of underwater hockey players during exercise. Materials and Methods: Hydration status (fluid intake/loss amounts, repeatedly weight measurements) and tissue oxygen saturation measurements of 14 underwater hockey players were performed before and after the land/water training, separately. Hydration status was assessed by monitoring weight and urine specific gravity (USG) measurements, whereas tissue oxygen saturation was measured by using finger-type pulse oximeter. Results: The study was completed with14 elite players (age=19.4±6.2 years, female=4(29%), and male=10(71%)). The body fat percentage was calculated to be male:14.2±9.4%; female: 18.8±4.0%. The mean USG of athletes was determined to be 1020.1±5.6 g/cm3. During the water training, only 5 athletes consumed water (680±383.4 mL). All the athletes (except for 1 athlete [7.1%]) completed the training with loss of body fluid. Mean loss of water was 310±213.2 mL after land training and 723.1±501.9 mL after water training. Dehydration ratio was measured 0.97±0.64% after trainings. The first oxygen saturation was measured 96.1±1.6, that was decreased after water training (94.6±2.2; p=0.044, p=0.049). Pulse increased after water training in reverse proportion to oxygen saturation (p=0.004), but there was no difference between before and after land training (p=0.132). Conclusion: It was found that several Underwater hockey players began training dehydrated and loss of water continued since they didn’t consume enough water during training. Oxygen saturation significantly decreased after water training. Fluid consumption of underwater hockey players, especially during water training, should be monitored and adequate fluid consumption should be ensured.

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.

Evaluation of a low-cost portable NIRS device for monitoring muscle ischemia.

The main objective of this study is to evaluate the low-cost, open-source HEGduino device as a tissue oximetry monitor to advance the research of somatic NIRS monitoring. Specifically, this study analyzes the use of this portable functional NIRS system for detecting the cessation of blood flow due to vascular occlusion in an upper limb.19 healthy patients aged between 25 and 50 were recruited and monitored using HEGduino device. Participants underwent a vascular occlusion test on one forearm. Raw values collected by HEGduino as well as the processed variables derived from the measurements were registered. Additional variables to characterize the signal noise during the tests were also recorded.The results of the data distribution curves for all the subjects in the study accurately detected the physiological events associated with transient tissue ischemia. The statistical analysis of the recorded data showed that the difference between the baseline values recorded by the red led (RED) and its normalized minimum variable was always different from zero (p < 0.014). Furthermore, the difference between the normalized baseline values recorded by the infrared led (IR) and the corresponding normalized minimum value was also different from zero (p < 0.001). The R-squared coefficient of determination for the noise variables considered in this study on the normalized RED and IR values was 0.08 and 0.105, respectively.The study confirms the potential of HEGduino system to detect an interruption of the blood flow by means of variations in regional tissue oxygen saturation. This study demonstrates the potential of the HEGduino device as a monitoring alternative to advance the study of the applicability of NIRS in muscle tissue oximetry.

Enhancing eMSOT with nonlinear mixed model approaches for precise blood oxygenation imaging in tissues

Multispectral optoacoustic tomography (MSOT) utilizes multiple wavelengths to illuminate tissue, producing a series of optoacoustic images rich in spectral information. This approach offers a more comprehensive spectral profile compared to conventional optoacoustic techniques. Contrasted with single-wavelength optoacoustic images, the spectral information can be amalgamated with endogenous chromophores or exogenous dyes within biological organisms, thereby unveiling physiological, cellular, and subcellular functions. The development of eigenspectral optoacoustic tomography (eMSOT), grounded in the linear mixture model (LMM), along with its various derivative methods, facilitates label-free imaging of tissue oxygen saturation in deep-seated structures. However, the effectiveness of the LMM may diminish in the presence of multiple scattering effects or inter-substance interactions, thereby impairing the performance of the eMSOT method in heterogeneous tissues. To address this issue, we propose incorporating a nonlinear model to enhance the eMSOT technique, which we refer to as NL-eMSOT (non-linear eMSOT). This model employs the Hadamard product as a nonlinear component of the LMM, effectively characterizing the interactions between photons and both oxygenated and deoxygenated hemoglobin within the near-infrared spectral window. This innovation resolves the nonlinear unmixing problem inherent in optoacoustic imaging. Our approach, validated through numerical simulations, phantom experiments, and in vivo studies, improves the accuracy of quantitative oxygen saturation estimation in heterogeneous tissues by accounting for inter-substance interactions. Consequently, it necessitates the consideration of more complex mixing models to adequately address nonlinear interactions.

Exploring the impact and influence of melanin on frequency-domain near-infrared spectroscopy measurements.

Near-infrared spectroscopy (NIRS) is a non-invasive optical method that measures changes in hemoglobin concentration and oxygenation. The measured light intensity is susceptible to reduced signal quality due to the presence of melanin. We quantify the influence of melanin concentration on NIRS measurements taken with a frequency-domain near-infrared spectroscopy system using 690 and 830nm. Using a forehead NIRS probe, we measured 35 healthy participants and investigated the correlation between melanin concentration indices, which were determined using a colorimeter, and several key metrics from the NIRS signal. These metrics include signal-to-noise ratio (SNR), two measurements of oxygen saturation (arterial oxygen saturation, , and tissue oxygen saturation, ), and optical properties represented by the absorption coefficient ( ) and the reduced scattering coefficient ( ). We found a significant negative correlation between the melanin index and the SNR estimated in oxy-hemoglobin signals ( , ) and levels ( , ). However, no significant changes were observed in the optical properties and ( , ). We found that estimated SNR and values show a significant decline and dependence on the melanin index, whereas and optical properties do not show any correlation with the melanin index.

Intraoperative pneumatic tourniquet application reduces soft-tissue microcirculation, but without affecting wound healing in calcaneal fractures

BackgroundWound healing complications are a major challenge following the extended lateral approach in calcaneal fractures. Soft-tissue microcirculation plays an important role via the delivery of oxygen, nutrients, and the regulation of a local milieu. The aim of this clinical study was to examine the effect of intraoperative pneumatic tourniquet application on skin and subcutaneous microcirculation, and its impact on wound healing progression.MethodsPatients with calcaneal fractures were randomly assigned to two groups defined by a surgery conducted either with use or without use of a tourniquet. Blood flow (BF [AU]), tissue oxygen saturation (SO2[%]) and the relative amount of haemoglobin (rHb[AU]) were intraoperatively measured at two depths (2 and 8 mm) non-invasively by spectrophotometry (Micro-Lightguide O2C®, LEA Medizintechnik, Giessen, Germany). Time points were before and after inflation of the pneumatic tourniquet and also at the end of surgery before deflation. A linear mixed model (LMM) was fitted for statistical analysis.ResultsThirty-four patients (3 women and 31 men) with 37 calcaneal fractures were included. In 22 of them, the surgery was conducted with a tourniquet and in the other 15 without its use. A significant decrease of microcirculation, characterized by decreases in blood flow (p = 0.011) and tissue oxygenation (p = 0.023) was measured in 8 mm depth after inflating the tourniquet. However, these changes did not influence the time of postoperative wound healing.ConclusionThe use of a pneumatic tourniquet reduces deep microcirculation without affecting postoperative wound healing.Trial registration The study was registered in www.ClinicalTrials.gov (NCT01264146).

Benefits of chest wall mobilization on respiratory efficiency and functional exercise capacity in people with severe chronic obstructive pulmonary disease (COPD): A randomized controlled trial.

Coexistence of chest wall hypomobility and lung hyperinflation compromises respiratory muscle function and respiratory efficiency in people with severe chronic obstructive pulmonary disease (COPD). This study aimed to investigate the effect of chest wall mobilization on functional exercise capacity, respiratory muscle activity and respiratory muscle tissue oxygen saturation for people with severe COPD. Thirty male adults (age: 75 ± 6) diagnosed with severe COPD completed a 6-week programme (twice/week) according to intervention randomization (chest wall mobilization group, CWMG, n = 15; control group, CG, n = 15). Both groups received standardized education and walking exercise, while CWMG also received chest wall and thoracic spine mobilization. Electromyography of the essential and accessory respiratory muscles and tissue oxygen saturation of the intercostal muscle (StO2, measured by near-infrared spectroscopy) during incremental cycle exercise test were measured and compared between the two groups at pre-programme, post-programme and 3-month follow-up. Patients in CWMG demonstrated a significant increase in exercise tolerance from <3 METS to 4-6 METS (p = 0.000) after intervention. A significant decrease in activity of scalene, sternocleidomastoids and intercostal muscle during exercise test (p < 0.01) was found in CWMG, as compared to CG. A significant decrease in StO2 (p < 0.05) and greater decline in the slope of oxygenation dissociation (p = 0.000) were seen in CWMG during exercise test. These positive results were maintained at 3-month follow-up in CWMG. Improvements in exercise tolerance, respiratory muscle efficiency and oxygenation extraction ability in CWMG suggest a potential clinical benefit of integrating chest wall and thoracic spine mobilization for rehabilitation of people with severe COPD.

Wavelength selection for real-time detection of human stress based on StO2

Hyperspectral imaging (HSI) has been used to detect human stress by extracting tissue oxygen saturation (StO2). However, extracting StO2 from raw HSI data requires a large number of wavelengths, which prevents real-time human stress detection. In this study, we present a wavelength selection framework for real-time detection of human stress. Leveraging the simplicity of linear prediction (LP) and the self-organizing optimization of physarum network (PN), we design the LPPN algorithm to select a small number of feature bands from the traditional band of 516-580 nm (containing 106 wavelengths) to extract StO2. Subsequently, we propose an evaluation criterion “score” based on comprehensive consideration of multiple factors to select the optimal wavelengths. The optimal 4-band combination is targeted and its robustness is confirmed. The StO2 extracted by the optimal 4-band combination is highly correlated (correlation coefficient = 0.9580) and shares the same distribution pattern with the original StO2. Using the StO2 extracted by the optimal 4-band for real-time stress detection, the accuracy of four-class stress detection can reach 74.76%. These results indicate that the real-time extraction of StO2 and detection of human stress are possible and the proposed framework is promising.

A personalized clinical assessment: multi-sensor approach for understanding musculoskeletal health in the frail population

BackgroundSarcopenia is a muscle disorder causing a progressive reduction of muscle mass and strength, but the mechanism of its manifestation is still partially unknown. The three main parameters to assess are: muscle strength, muscle volume or quality and low physical performance. There is not a definitive approach to assess the musculoskeletal condition of frail population and often the available tests to be performed in those clinical bedridden patients is reduced because of physical impairments. In this paper, we propose a novel instrumental multi-domain and non-invasive approach during a well-defined protocol of measurements for overcoming these limitations. A group of 28 bedridden elder people, subjected to surgery after hip fracture, was asked to perform voluntary isometric contractions at the 80% of their maximum voluntary contraction with the non-injured leg. The sensor employed before and/or during the exercise were: ultrasound to determine the muscle architecture (vastus lateralis); force acquisition with a load cell placed on the chair, giving an indication of the muscle strength; surface electromyography (EMG) for monitoring muscular electrical activity; time-domain (TD) near-infrared spectroscopy (NIRS) for evaluating muscle oxidative metabolism.ResultsA personalized “report card” for each subject was created. It includes: the force diagram (both instantaneous and cumulative, expected and measured); the EMG–force diagram for a comparison between EMG derived median frequency and measured force; two graphs related to the hemodynamic parameters for muscle oxidative metabolism evaluation, i.e., oxy-, deoxy-, total-hemoglobin and tissue oxygen saturation for the whole exercise period. A table with the absolute values of the previous hemodynamic parameters during the rest and the ultrasound related parameters are also included.ConclusionsIn this work, we present the union of protocols, multi-domain sensors and parameters for the evaluation of the musculoskeletal condition. The novelties are the use of sensors of different nature, i.e., force, electrical and optical, together with a new way to visualize and combine the results, by means of a concise, exhaustive and personalized medical report card for each patient. This assessment, totally non-invasive, is focused on a bedridden population, but can be extended to the monitoring of rehabilitation progresses or of the training of athletes.

In vivo optical assessment of cerebral and skeletal muscle microvascular response to phenylephrine.

This study aimed to investigate the simultaneous response of the cerebral and skeletal muscle microvasculature to the same phenylephrine (PE) boluses. A hybrid optical system that combines hyperspectral near-infrared spectroscopy (hs-NIRS) and diffuse correlation spectroscopy (DCS) was used to monitor changes in tissue oxygenation and perfusion. Data were collected from the head and hind limb of seven male Sprague-Dawley rats while administering intravenous (IV) injections of PE or saline to all animals. The response to saline was used as a control. Skeletal muscle oxygenation decreased significantly after PE injection, while a statistically underpowered decrease in perfusion was observed, followed by an increase beyond baseline. Vascular conductance also decreased in the muscle reflecting the drug's vasoconstrictive effects. Tissue oxygenation and perfusion increased in the brain in response to PE. Initially, there was a sharp increase in cerebral perfusion but no changes in cerebral vascular conductance. Subsequently, cerebral flow and vascular conductance decreased significantly below baseline, likely reflecting autoregulatory mechanisms to manage the excess flow. Further, fitting an exponential function to the secondary decrease in cerebral perfusion and increase in muscular blood flow revealed a quicker kinetic response in the brain to adjust blood flow. In the skeletal muscle, PE caused a transient decrease in blood volume due to vasoconstriction, which resulted in an overall decrease in hemoglobin content and tissue oxygen saturation. Since PE does not directly affect cerebral vessels, this peripheral vasoconstriction shunted blood into the brain, resulting in an initial increase in oxygenated hemoglobin and oxygen saturation.

Effects of preterm birth on the pattern of altitude acclimatization at rest and during moderate-intensity exercise across three days at 3,375 m.

Preterm birth elicits long-lasting physiological effects in various organ systems, potentially modulating exercise and environmental stress responses. To establish whether prematurely-born adults respond uniquely during early high-altitude acclimatization at rest and during exercise, 17 healthy adults born preterm (gestational age < 32 wk) and 17 term-born, age- and aerobic-capacity-matched, control participants completed a three-day high-altitude sojourn (3,375 m). Oxygen uptake, pulmonary ventilation, and hemodynamic responses, as well as pulse oxygen saturation, brain tissue saturation index (TSI), and skeletal muscle TSI, were measured daily at rest and during moderate-intensity steady-state exercise bouts. In general, the prematurely-born group displayed comparable acclimatization responses at rest, with similar ventilation and cardiac output observed between groups throughout. Resting brain TSI was, however, higher in the preterm group upon arrival at high altitude (72 ± 7% vs. 68 ± 3%; d = 1.20). Absolute exercising oxygen uptake was lower in the preterm participants (P = 0.047), with this group displaying lower exercising cardiac output underpinned by reduced stroke volume (both P = 0.035). Nevertheless, exercising minute ventilation (V̇e) did not differ between groups (P = 0.237) while brain TSI (70 ± 6% vs. 66 ± 3%; d = 1.35) and pulse oxygen saturation (85 ± 3% vs. 82 ± 5%; d = 1.52) were higher with prematurity upon arrival to high altitude. These findings suggest that healthy prematurely-born adults exhibit comparable early acclimatization patterns to their term-born counterparts and better maintain cerebral oxygenation at rest. Together, these data suggest that prematurely-born adults should not be discouraged from high-altitude sojourns involving physical activity.NEW & NOTEWORTHY The acclimatization pattern across three days at 3,375 m, at rest and during moderate-intensity exercise, was similar between healthy adults born prematurely and their term-born counterparts. Preterm adults free from respiratory complications were found to better maintain brain tissue and capillary oxygen saturation at high altitudes, whereas the term-born group experienced larger altitude-induced reductions. Despite apparent cardiac limitations, preterm individuals tolerated exercise similarly to their term-born peers. These findings underscore the notion that preterm birth per se does not predispose healthy adults to decreased altitude tolerance during exercise.

Effects of Intermittent Hypoxia Protocols on Cognitive Performance and Brain Health in Older Adults Across Cognitive States: A Systematic Literature Review.

The rise in the aging population highlights the need to address cognitive decline and neurodegenerative diseases. Intermittent hypoxia (IH) protocols show promise in enhancing cognitive abilities and brain health. This review evaluates IH protocols' benefits on cognition and brain health in older adults, regardless of cognitive status. A systematic search following PRISMA guidelines was conducted across four databases (PubMed, Scopus, Web of Science, and Cochrane Library) and two registers, covering records from inception to May 2024 (PROSPERO: CRD42023462177). Inclusion criteria were: 1) original research with quantitative details; 2) studies involving older adults, with or without cognitive impairment; 3) studies including IH protocols; 4) articles analyzing cognition and brain health in older adults. Seven studies and five registered trials met the criteria. Findings indicate that Intermittent Hypoxia Training (IHT) and Intermittent Hypoxia-Hyperoxia Training (IHHT) improved cognitive functions and brain health. Intermittent Hypoxic Exposure (IHE) improved cerebral tissue oxygen saturation, middle cerebral arterial flow velocity, and cerebral vascular conductance, particularly in cognitively impaired populations. IHT and IHHT had no significant effect on BDNF levels. There is a lack of studies on IHHE in older adults with and without cognitive impairment. IH protocols may benefit cognition regardless of cognitive status. IHT and IHE positively affect cerebral outcomes, with all protocols having limited effects on BDNF levels. Future research should standardize IH protocols, investigate long-term cognitive effects, and explore neuroprotective biomarkers. Combining these protocols with physical exercise across diverse populations could refine interventions and guide targeted therapeutic strategies.

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

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

Flowmetry and spectrophotometry can detect reduced intestinal microperfusion in nonsurvivors during equine colic surgery for large intestinal strangulation.

To evaluate the use of laser Doppler flowmetry and spectrophotometry (LDFS) for large intestinal viability assessment in horses with naturally occurring large intestinal strangulations. By use of LDFS, intestinal microperfusion was quantified as tissue oxygen saturation (tSo2), hemoglobin (tHB), and blood flow (tBF) in cases with large colon volvulus and small colon strangulations undergoing colic surgery (n = 17). Intestinal biopsies were taken from the pelvic flexure in all large colon cases and in small colon cases that underwent intraoperative euthanasia. Measurements were compared between survivors and nonsurvivors, and the correlation between LDFS and (immuno)histology was tested (P < .05). The tSo2 and tBF were clearly lower and tHB was higher than previously reported in healthy horses. Following correction of the lesion, pelvic flexure tBF was significantly lower than that of the left ventral colon. Prior to correction of the lesion, microperfusion did not differ between survivors and nonsurvivors, but following release of the strangulation the survivors had a significantly higher tSo2 and tBF compared to the nonsurvivors. There was a negative correlation between tBF and interstitium-to-crypt ratio and a positive correlation between tHB and the histological hemorrhage score. There were no significant correlations between LDFS measurements and inflammatory cell counts or hypoxia-inducible factor-1α immunoreactivity. Large intestinal microperfusion was decreased in nonsurvivors compared to survivors and was correlated with histological injury, suggesting that LDFS has the potential to predict tissue injury and postoperative survival. The use of LDFS as an ancillary diagnostic aid may improve intraoperative viability assessment during colic surgery.

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.