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Adequate exercise prescription requires a deep understanding of the body’s response to exercise. This study explored the responses of heart rate (HR), muscle oxygen saturation (SmO2), and perceived exertion (RPE) during six body-weight squat exercise variations. A total of 15 recreationally active participants (age: 28.2 ± 8.0 years; body mass: 71.1 ± 11.2 kg; height: 1.73 ± 0.08 m) were recruited. Six body-weight squat variations (deep, jumping, single-leg, uneven, unstable, and wall-sit) were randomly performed for 90 s. Results revealed that the jumping squat promoted a higher average and peak HR (165.3 ± 14.5 and 146.1 ± 14.8 bpm, respectively), and a lower average SmO2 and higher deoxygenation SmO2 in the soleus muscle (40.3 ± 15.4 and 46.0 ± 11.4%, accordingly). No differences were observed in recovery time or in the same SmO2 derived-parameters in the vastus lateralis muscle. The jumping variation promoted a greater response at a physiological level, both centrally, related to cardiovascular response, and peripherally, related to soleus SmO2. It was also the more demanding variation at both the overall and lower limb muscular level of RPE. This holistic view allows a precise identification of the response patterns in body-weight squat exercise variations to an acute session, with a training intervention providing additional information.

BackgroundMinimising hypoxaemia during submaximal walking tests has a positive effect on exercise capacity and dyspnoea in patients with chronic obstructive pulmonary disease (COPD) on long-term oxygen therapy (LTOT). However, the impact of optimising oxygenation during everyday tasks remains unexplored. Therefore, we investigated the effects of maintaining a target saturation on activities of daily living (ADL) using automated oxygen titration compared with conventional fixed oxygen flow.MethodsIn a double-blinded, randomised crossover trial, patients with COPD on LTOT performed two GlittreADL tests to assess the functional capacity of everyday activities using (1) their fixed oxygen dose and (2) an adjusted flow from 0 to 8 L/min targeting a peripheral oxygen saturation (SpO2) of 90–94%. A closed-loop device automatically titrated the oxygen based on information from a Bluetooth wrist pulse oximeter.Results31 patients (mean±SD age: 72.8±5.9 years, forced expiratory volume in 1 s of % predicted: 36.7±12.7) were included. The patients reduced the time to perform the ADL test by median (IQR) 38 (12–73) s, p<0.001, using automated titration compared with the fixed oxygen flow. The oxygen flow in the automated arm more than tripled to 5.4 (4.1–6.8) versus 1.6 (1.1–2.1) L/min (fixed) during the test, p<0.001, while the time spent within SpO2-target was increased from 19% to 49%, p=0.002. Correspondingly, the patients experienced less dyspnoea (BorgCR10); 5 (3–7) versus 6 (4–8), p<0.001, in favour of the automated oxygen titration.ConclusionsImproving oxygenation and extending the time spent within target saturation reduced dyspnoea and improved functional capacity in ADL in patients with COPD on LTOT.Trial registration numberNCT05553847.

Quantification of pain or discomfort induced by pressure is essential for understanding human responses to physical stimuli and improving user interfaces. Pain research has been conducted to investigate physiological signals associated with discomfort and pain perception. This study analyzed changes in electrodermal activity (EDA), tissue oxygen saturation (StO2), heart rate variability (HRV), and Visual Analog Scale (VAS) under pressures of 10, 20, and 30 kPa applied for 3 min to the thigh, knee, and calf in a seated position. Twenty participants were tested, and relationships between biosignals, pressure intensity, and pain levels were evaluated using Friedman tests and post-hoc analyses. Multiple linear regression models were used to predict VAS and pressure, and five machine learning models (SVM, Logistic Regression, Random Forest, MLP, KNN) were applied to classify pain levels (no pain: VAS 0, low: VAS 1–3, moderate: VAS 4–6, high: VAS 7–10) and pressure intensity. The results showed that higher pressure intensity and pain levels affected sympathetic nervous system responses and tissue oxygen saturation. Most EDA features and StO2 significantly changed according to pressure intensity and pain levels, while NN interval and HF among HRV features showed significant differences based on pressure intensity or pain level. Regression analysis combining biosignal features achieved a maximum R2 of 0.668 in predicting VAS and pressure intensity. The four-level classification model reached an accuracy of 88.2% for pain levels and 81.3% for pressure intensity. These results demonstrated the potential of EDA, StO2, HRV signals, and combinations of biosignal features for pain quantification and prediction.

Background During the COVID-19 pandemic, there have been concerns regarding potential bias in pulse oximetry measurements for people with high levels of skin pigmentation. We systematically reviewed the effects of skin pigmentation on the accuracy of oxygen saturation measurement by pulse oximetry (SpO 2 ) compared with the gold standard SaO 2 measured by CO-oximetry. Methods We searched Ovid MEDLINE, Ovid Embase, EBSCO CINAHL, ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform (up to December 2021) for studies with SpO 2 –SaO 2 comparisons and measuring the impact of skin pigmentation or ethnicity on pulse oximetry accuracy. We performed meta-analyses for mean bias (the primary outcome in this review) and its standard deviations (SDs) across studies included for each subgroup of skin pigmentation and ethnicity and used these pooled mean biases and SDs to calculate accuracy root-mean-square ( A rms ) and 95% limits of agreement. The review was registered with the Open Science Framework ( https://osf.io/gm7ty ). Results We included 32 studies (6505 participants): 15 measured skin pigmentation and 22 referred to ethnicity. Compared with standard SaO 2 measurement, pulse oximetry probably overestimates oxygen saturation in people with the high level of skin pigmentation (pooled mean bias 1.11%; 95% confidence interval 0.29 to 1.93%) and people described as Black/African American (1.52%; 0.95 to 2.09%) (moderate- and low-certainty evidence). The bias of pulse oximetry measurements for people with other levels of skin pigmentation or those from other ethnic groups is either more uncertain or suggests no overestimation. Whilst the extent of mean bias is small or negligible for all subgroups evaluated, the associated imprecision is unacceptably large (pooled SDs > 1%). When the extent of measurement bias and precision is considered jointly, pulse oximetry measurements for all the subgroups appear acceptably accurate (with A rms  < 4%). Conclusions Pulse oximetry may overestimate oxygen saturation in people with high levels of skin pigmentation and people whose ethnicity is reported as Black/African American, compared with SaO 2 . The extent of overestimation may be small in hospital settings but unknown in community settings. Review protocol registration https://osf.io/gm7ty

Near-infrared spectroscopy (NIRS) to monitor muscle oxygen saturation (SmO2) is rapidly expanding into applied sports settings. However, the technology is limited due to its inability to convey quantifiable values. A test battery to assess reliability and validity of a 0% to 100% scale modeled by a commercially available NIRS device was established. This test battery applies a commonly used technique, the arterial occlusion method (AOM) to assess repeatability, reproducibility, and face validity. A total of 22 participants completed the test battery to scrutinize the 0% to 100% scale provided by the device. All participants underwent repeated AOM tests in passive and active conditions. The SmO2 minimum and SmO2 maximum values were obtained from the AOM and were used in the subsequent analysis. Repeatability and reproducibility were tested for equivalency and Bland–Altman plots were generated. Face validity was assessed by testing SmO2 values against an a priori defined threshold for mixed venous blood during AOM response. The device exhibits an appropriately functional 0% to 100% scale that is reliable in terms of repeatability and reproducibility. Under the conditions applied in the test battery design, the device is considered valid for application in sports.

Abstract Objective To assess whether perioperative management guided by near-infrared spectroscopy to determine tissue oxygen saturation and haemodynamic monitoring reduces postoperative complications after off-pump coronary artery bypass grafting. Design Assessor blinded, single centre, randomised controlled trial (Bottomline-CS trial). Setting A tertiary teaching hospital in China. Participants 1960 patients aged 60 years or older who were scheduled for elective off-pump coronary artery bypass grafting. Interventions All patients had multisite monitoring of tissue oxygen saturation (bilateral forehead and unilateral forearm brachioradialis) and haemodynamic monitoring. Both groups received usual care, including arterial blood pressure, central venous pressure, electrocardiography, and transoesophageal echocardiography when indicated. Guided care aimed to maintain tissue oxygenation within 10% above or below preoperative baseline values, established 24-48 hours before surgery, from the start of anaesthesia until extubation or for up to 24 hours postoperatively. In the usual care group, tissue oximetry and haemodynamic data were concealed, and care was routine. Main outcome measures The primary outcome was the incidence of a composite of 30 day postoperative complications, which were cerebral, cardiac, respiratory, renal, infectious, and mortality complications. Secondary outcomes included the individual components of the composite outcome, new-onset atrial fibrillation, and hospital length of stay. Results Of 1960 patients randomly assigned, data from 967 guided care and 974 usual care patients were analysed. During anaesthesia, the area under the curve for tissue oxygen saturation measurements outside the plus and minus 10% baseline range was significantly smaller with guided care than only usual care: left forehead 32.4 versus 57.6 (%×min, P<0.001), right forehead 37.9 versus 62.6 (P<0.001), and forearm 14.8 versus 44.7 (P<0.001). The primary composite outcome occurred in 457/967 (47.3%) patients in the guided care group and 466/974 (47.8%) patients in the usual care group (unadjusted risk ratio 0.99 (95% confidence interval 0.90 to 1.08), P=0.83). No secondary outcomes differed significantly between groups. The largest observed difference was in incidence of pneumonia, which was less frequent in the guided care group (88/967, 9.1%) than in the usual care group (121/974, 12.4%) and not statistically significant after adjusting for multiple comparisons. Conclusions Guided care by use of multisite near-infrared spectroscopy and haemodynamic monitoring effectively maintained tissue oxygenation near baseline levels compared with usual care. However, no clear evidence was noted that this approach reduced the incidence of major postoperative complications. These findings do not support the routine use of near-infrared spectroscopy and haemodynamic monitoring to maintain tissue oxygenation during off-pump coronary artery bypass grafting. Trial registration ClinicalTrials.gov NCT04896736.

Acute ingestion of exogenous ketone supplements in the form of a (R)‐3‐hydroxybutyl (R)‐3‐hydroxybutyrate (R‐BD R‐βHB) ketone monoester (KME) can attenuate declines in oxygen availability during hypoxic exposure and might impact cognitive performance at rest and in response to moderate‐intensity exercise. In a single‐blind randomized crossover design, 16 males performed assessments of cognitive performance before and during hypoxic exposure with moderate exercise [2 × 20 min weighted ruck (∼22 kg) at 3.2 km/h at 10% incline] in a normobaric altitude chamber (4572 m, 11.8% O2). The R‐BD R‐βHB KME (573 mg/kg) or a calorie‐ and taste‐matched placebo (∼50 g maltodextrin) were co‐ingested with 40 g of dextrose before exposure to hypoxia. The R‐βHB concentrations were rapidly elevated and sustained (>3 mM; P < 0.001) by KME. The decline in oxygen saturation during hypoxic exposure was attenuated in KME conditions by 2.4%–4.2% (P < 0.05) compared with placebo. Outcomes of cognitive performance tasks, in the form of the Defense Automated Neurobehavioral Assessment (DANA) code substitution task, the Stroop color and word task, and a shooting simulation, did not differ between trials before and during hypoxic exposure. These data suggest that the acute exogenous ketosis induced by KME ingestion can attenuate declining blood oxygen saturation during acute hypoxic exposure both at rest and during moderate‐intensity exercise, but this did not translate into differences in cognitive performance before or after exercise in the conditions investigated. What is the central question of this study? Can exogenous ketosis act as a countermeasure to declines in blood oxygen saturation and cognitive performance during acute hypoxic exposure while performing a weighted ruck exercise? What is the main finding and its importance? Acute exogenous ketosis via ingestion of a drink containing the (R)‐3‐hydroxybutyl (R)‐3‐hydroxybutyrate ketone monoester prior to acute hypoxic exposure attenuated hypoxia‐induced declines in blood oxygen saturation but had no effect on cognitive performance during exercise.

PurposePatients receiving venoarterial extracorporeal membrane oxygenation (VA-ECMO) frequently develop arterial hyperoxaemia, which may be harmful. However, lower oxygen saturation targets may also lead to harmful episodes of hypoxaemia.MethodsIn this registry-embedded, multicentre trial, we randomly assigned adult patients receiving VA-ECMO in an intensive care unit (ICU) to either a conservative (target SaO2 92–96%) or to a liberal oxygen strategy (target SaO2 97–100%) through controlled oxygen administration via the ventilator and ECMO gas blender. The primary outcome was the number of ICU-free days to day 28. Secondary outcomes included ICU-free days to day 60, mortality, ECMO and ventilation duration, ICU and hospital lengths of stay, and functional outcomes at 6 months.ResultsFrom September 2019 through June 2023, 934 patients who received VA-ECMO were reported to the EXCEL registry, of whom 300 (192 cardiogenic shock, 108 refractory cardiac arrest) were recruited. We randomised 149 to a conservative and 151 to a liberal oxygen strategy. The median number of ICU-free days to day 28 was similar in both groups (conservative: 0 days [interquartile range (IQR) 0–13.7] versus liberal: 0 days [IQR 0–13.3], median treatment effect: 0 days [95% confidence interval (CI) – 3.1 to 3.1]). Mortality at day 28 (59/149 [39.6%] vs 59/151 [39.1%]) and at day 60 (64/149 [43%] vs 62/151 [41.1%] were similar in conservative and liberal groups, as were all other secondary outcomes and adverse events. The conservative group experienced 44 (29.5%) major protocol deviations compared to 2 (1.3%) in the liberal oxygen group (P < 0.001).ConclusionsIn adults receiving VA-ECMO in ICU, a conservative compared to a liberal oxygen strategy, did not affect the number of ICU-free days to day 28.

Fidgety movements provide early information about a potential development of cerebral palsy in preterm neonates. The aim was to assess differences in the combined outcome of mortality and fidgety movements defined as normal or pathological in very preterm neonates according to the group allocation in the randomised-controlled multicentre COSGOD III trial. Preterm neonates of two centres participating in the COSGOD III trial, whose fidgety movements were assessed as normal or pathological at six to 20 weeks of corrected age, were analysed. In the COSGOD III trial cerebral oxygen saturation (crSO 2 ) was measured by near-infrared spectroscopy (NIRS) during postnatal transition and guided resuscitation in preterm neonates randomised to the NIRS-group, whereby medical support was according routine, as it was also in the control group. Fidgety movements were classified in normal or abnormal/absent at six to 20 weeks of corrected age. Mortality and fidgety movements of preterm neonates allocated to the NIRS-group were compared to the control-group. Normal outcome was defined as survival with normal fidgety movements. One-hundred-seventy-one preterm neonates were included (NIRS-group n  = 82; control-group n  = 89) with a median gestational age of 29.4 (27.4–30.4) and 28.7 (26.7–31.0) weeks in the NIRS-group and the control-group, respectively. There were no differences in the combined outcome between the two groups: 90.2% of the neonates in the NIRS-group and 89.9% in the control-group survived with normal outcome (relative risk [95% CI]; 0.96 [0.31–2.62]). Conclusions : In the present cohort of preterm neonates, monitoring of crSO 2 and dedicated interventions in addition to routine care during transition period after birth did not show an impact on mortality and fidgety movements defined as normal or pathological at six to 20 weeks corrected age. What is Known • Fidgety movements display early spontaneous motoric pattern and may provide early information about a potential development of cerebral palsy in preterm neonates.   What is New   • This retrospective observational study of the randomised-controlled multicentre COSGOD III trial is the first study investigating the potential influence of cerebral oxygenation guided resuscitation during postnatal transition period on combined outcome of mortality and fidgety movements up to 20 weeks of corrected age in very preterm neonates. • This study adds to the growing interest of assessing cerebral oxygenation, that monitoring of cerebral oxygen saturation and dedicated interventions during postnatal transition period according to the COSGOD III trial has no significant influence on mortality and fidgety movements defined as normal or pathological in very preterm neonates.

BackgroundPassengers on long-haul flights frequently consume alcohol. Inflight sleep exacerbates the fall in blood oxygen saturation (SpO2) caused by the decreased oxygen partial pressure in the cabin. We investigated the combined influence of alcohol and hypobaric hypoxia on sleep, SpO2 and heart rate.MethodsTwo groups of healthy individuals spent either two nights with a 4-hour sleep opportunity (00:00–04:00 hours) in the sleep laboratory (n=23; 53 m above sea level) or in the altitude chamber (n=17; 753 hPa corresponding to 2438 m above sea level, hypobaric condition). Participants consumed alcohol before one of the nights (mean±SE blood alcohol concentration 0.043±0.003%). The order of the nights was counterbalanced. Two 8-hour recovery nights (23:00–07:00 hours) were scheduled between conditions. Polysomnography, SpO2 and heart rate were recorded.ResultsThe combined exposure to alcohol and hypobaric condition decreased SpO2 to a median (25th/75th percentile) of 85.32% (82.86/85.93) and increased heart rate to a median (25th/75th percentile) of 87.73 bpm (85.89/93.86) during sleep compared with 88.07% (86.50/88.49) and 72.90 bpm (70.90/78.17), respectively, in the non-alcohol hypobaric condition, 94.97% (94.59/95.33) and 76.97 bpm (65.17/79.52), respectively, in the alcohol condition and 95.88% (95.72/96.36) and 63.74 bpm (55.55/70.98), respectively, in the non-alcohol condition of the sleep laboratory group (all p<0.0001). Under the combined exposure SpO2 was 201.18 min (188.08/214.42) below the clinical hypoxia threshold of 90% SpO2 compared with 173.28 min (133.25/199.03) in the hypobaric condition and 0 min (0/0) in both sleep laboratory conditions. Deep sleep (N3) was reduced to 46.50 min (39.00/57.00) under the combined exposure compared with both sleep laboratory conditions (alcohol: 84.00 min (62.25/92.75); non-alcohol: 67.50 min (58.50/87.75); both p<0.003).ConclusionsThe combination of alcohol and inflight hypobaric hypoxia reduced sleep quality, challenged the cardiovascular system and led to extended duration of hypoxaemia (SpO2 <90%).