Hyperoxia Improves Hemodynamic Status During Head-up Tilt Testing in Healthy Volunteers A Randomized Study

International audienceHead-up tilt test is useful for exploring neurally mediated syncope. Adenosine is an ATP derivative implicated in cardiovascular disturbances that occur during head-up tilt test. The aim of the present study was to investigate the impact of hyperoxia on adenosine plasma level and on hemodynamic changes induced by head-up tilt testing. Seventeen healthy male volunteers (mean age 35 AE 11 years) were included in the study. The experiment consisted of 2 head-up tilt tests, 1 session with subjects breathing, through a mask, medical air (FiO 2 ¼ 21%) and 1 session with administration of pure oxygen (FiO 2 ¼ 100%) in double-blind manner. Investigations included continuous monitoring of hemodynamic data and measurement of plasma adenosine levels. No presyncope or syncope was found in 15 of the 17 volunteers. In these subjects, a slight decrease in systolic blood pressure was recorded during orthostatic stress performed under medical air exposure. In contrast, hyperoxia led to increased systolic blood pressure during orthostatic stress when compared with medical air. Furthermore, mean adenosine plasma levels decreased during hyperoxic exposure before (0.31 AE 0.08 mM) and during head-up tilt test (0.33 AE 0.09 mM) when compared with baseline (0.6 AE 0.1 mM). Adenosine plasma level was unchanged during medical air exposure at rest (0.6 AE 0.1 mM), and slightly decreased during orthostatic stress. In 2 volunteers, the head-up tilt test induced a loss of consciousness when breathing air. In these subjects, adenosine plasma level increased during orthostatic stress. In contrast, during hyperoxic exposure, the head-up tilt test did not induce presyncope or syncope. In these 2 volunteers, biological study demonstrated a decrease in adenosine plasma level at both baseline and during orthostatic stress for hyperoxic exposure compared with medical air. These results suggest that hyperoxia was able to increase blood pressure during head-up tilt test via a decrease in plasma adenosine concentration. Our results also suggest that adenosine receptor antagonists are worth trying in neurocardiogenic syncope. (Medicine 95(8):e2876) Abbreviations: AR = adenosine receptor, APL = adenosine plasma level, BP = blood pressure, DBP = diastolic blood pressure, FiO 2 = fraction of inspired oxygen, HR = heart rate, HUT = head-up tilt test, LMM = linear mixed model, PO 2 = partial pressure of oxygen, SBP = systolic blood pressure

A cross-sectional study assessing the contributions of body fat mass and fat-free mass to body mass index scores in male youth rugby players

Background. In some sports such as rugby, a large body size is an advantage, and the desire to gain weight can bring young players to become overweight or obese. The aim of this study was to evaluate the prevalence of overweight and obesity and the contribution of body fat mass index (BFMI) and fat-free mass index (FFMI) to body mass index (BMI) changes among young male rugby players (15-a-side rugby). Methods. The criteria of the International Obesity Task Force were used to define overweight and obesity from BMI. The method of skinfold thickness was used to assess percentage of body fat (%BF), BFMI, and FFMI. Excess body fat was defined by using BFMI and %BF above the 75th percentile. Data were grouped according to the age categories of the French Rugby Federation (U11, under 11 years; U13, under 13 years; U15, under 15 years) and to BMI status (NW normal-weight versus OW/OB overweight/obese). Results. Overall, 32.8% of the young players were overweight, and 13.8% were obese. However, 53% of young players classified as obese and overweight by BMI had an excess body fat by using BFMI above the 75th percentile. FFMI increased significantly between U11 and U13 in both groups, without significant change in BMI and BFMI. Both groups had similar significant gains in BMI and FFMI between U13 and U15, while BFMI only increased significantly in OW/OB (+ 18.5%). The strong correlations between BMI and %BF were systematically lower than those between BMI and BFMI. FFMI was strongly or moderately associated with BFMI. Conclusions. Chart analysis of BFMI and FFMI could be used to distinguish changes in body composition across age categories in young male rugby players classified as normal-weight, overweight, and obese by BMI

Mental Workload Alters Heart Rate Variability, Lowering Non-linear Dynamics

Mental workload is known to alter cardiovascular function leading to increased cardiovascular risk. Nevertheless, there is no clear autonomic nervous system unbalance to be quantified during mental stress. We aimed to characterize the mental workload impact on the cardiovascular function with a focus on heart rate variability (HRV) non-linear indexes. A 1-h computerized switching task (letter recognition) was performed by 24 subjects while monitoring their performance (accuracy, response time), electrocardiogram and blood pressure waveform (finger volume clamp method). The HRV was evaluated from the beat-to-beat RR intervals (RRI) in time-, frequency-, and informational- domains, before (Control) and during the task. The task induced a significant mental workload (visual analog scale of fatigue from 27 ± 26 to 50 ± 31 mm, p < 0.001, and NASA-TLX score of 56 ± 17). The heart rate, blood pressure and baroreflex function were unchanged, whereas most of the HRV parameters markedly decreased. The maximum decrease occurred during the first 15 min of the task (P1), before starting to return to the baseline values reached at the end of the task (P4). The RRI dimension correlation (D2) decrease was the most significant (P1 vs. Control: 1.42 ± 0.85 vs. 2.21 ± 0.8, p < 0.001) and only D2 lasted until the task ended (P4 vs. Control: 1.96 ± 0.9 vs. 2.21 ± 0.9, p < 0.05). D2 was identified as the most robust cardiovascular variable impacted by the mental workload as determined by posterior predictive simulations (p = 0.9). The Spearman correlation matrix highlighted that D2 could be a marker of the generated frustration (R = –0.61, p < 0.01) induced by a mental task, as well as the myocardial oxygen consumption changes assessed by the double product (R = –0.53, p < 0.05). In conclusion, we showed that mental workload sharply lowered the non-linear RRI dynamics, particularly the RRI correlation dimension

Extended Driving Impairs Nocturnal Driving Performances

Though fatigue and sleepiness at the wheel are well-known risk factors for traffic accidents, many drivers combine extended driving and sleep deprivation. Fatigue-related accidents occur mainly at night but there is no experimental data available to determine if the duration of prior driving affects driving performance at night. Participants drove in 3 nocturnal driving sessions (3–5am, 1–5am and 9pm–5am) on open highway. Fourteen young healthy men (mean age [±SD] = 23.4 [±1.7] years) participated Inappropriate line crossings (ILC) in the last hour of driving of each session, sleep variables, self-perceived fatigue and sleepiness were measured. Compared to the short (3–5am) driving session, the incidence rate ratio of inappropriate line crossings increased by 2.6 (95% CI, 1.1 to 6.0; P<.05) for the intermediate (1–5am) driving session and by 4.0 (CI, 1.7 to 9.4; P<.001) for the long (9pm–5am) driving session. Compared to the reference session (9–10pm), the incidence rate ratio of inappropriate line crossings were 6.0 (95% CI, 2.3 to 15.5; P<.001), 15.4 (CI, 4.6 to 51.5; P<.001) and 24.3 (CI, 7.4 to 79.5; P<.001), respectively, for the three different durations of driving. Self-rated fatigue and sleepiness scores were both positively correlated to driving impairment in the intermediate and long duration sessions (P<.05) and increased significantly during the nocturnal driving sessions compared to the reference session (P<.01). At night, extended driving impairs driving performances and therefore should be limited

RCEA: Real-time, Continuous Emotion Annotation for collecting precise mobile video ground truth labels

Collecting accurate and precise emotion ground truth labels for mobile video watching is essential for ensuring meaningful predictions. However, video-based emotion annotation techniques either rely on post-stimulus discrete self-reports, or allow real-time, continuous emotion annotations (RCEA) only for desktop settings. Following a user-centric approach, we designed an RCEA technique for mobile video watching, and validated its usability and reliability in a controlled, indoor (N=12) and later outdoor (N=20) study. Drawing on physiological measures, interaction logs, and subjective workload reports, we show that (1) RCEA is perceived to be usable for annotating emotions while mobile video watching, without increasing users' mental workload (2) the resulting time-variant annotations are comparable with intended emotion attributes of the video stimuli (classification error for valence: 8.3%; arousal: 25%). We contribute a validated annotation technique and associated annotation fusion method, that is suitable for collecting fine-grained emotion annotations while users watch mobile videos

Fatigue et somnolence, conséquences comportementales (Aspects attentionnels, reconnaissance et prise de décisions)

La fatigue et la somnolence modulent le niveau de l'éveil qui, à son tour, modules les performances de l'Homme à des tâches quotidiennes. La fatigue, d'une part, apparaît : 1) lorsqu'une activité est excessivement prolongée 2) de façon chronique, en cas de pathologies provoquant de l'asthénie. D'autre part, la somnolence apparaît : 1) en cas de veille prolongée et/ou 2) de veille nocturne, 3) lorsque le sommeil est fragmenté par une cause organique, 4) lorsque les systèmes d'éveil sont déficients par une cause neurologique. Sous le terme "performances à des tâches quotidiennes", se cachent tous les processus cognitifs qui interagissent profondément ensemble : l'attention, la reconnaissance et la prise de décision. L'attention peut être divisée en 2 sous-processus : l'attention soutenue qui est la capacité à maintenir son attention, à un niveau efficient et la sélection attentionnelle, qui est la capacité à filtrer les stimuli de l'environnement. La reconnaissance est la capacité à comparer l'information, une fois filtrée, à celle présente en mémoire. Enfin, la prise de décision est la capacité à choisir le comportement qui apparaît comme le plus adapté. Tous ces processus, mesurés de façon précise par des tâches expérimentales, ou de façon plus intégrée par des tâches "écologiques", sont affectés différemment lorsque le niveau d'éveil est altéré. Il restera toutefois à évaluer, 1) lorsque le participant est à son niveau d'éveil maximum, les différences de performances inter tâches puis 2) lorsque son niveau d'éveil diminue, à observer l'évolution différentielle de ses performances, enfin 3) à observer les différences interindividuelles de ces évolutions de performances.Level of wakefulness impacts human performances and is modulated by fatigue ans sleepiness. Fatigue occurred in case of extended lenght activity or when subjects suffered from asthenia caused by a disease. Sleepiness occured 1) when subjects were in extended wakefulness or/and 2) during noctural period 3) when sleep is fragmented by an organic disease 4) when awake systems are affected by a neurological disease. Human performances were sustained by a variety of cognitive processes which are strongly linked : attention, recognition and decision making. Attention could be divided in 2 major processes : sustained attention which is the ability to keep at an efficient level its attention and attentional selection which is the ability of filtering environment stimuli. Recognition is the precess which compares previous filtered information to memory representation. Desicion making is the ability to choose the most adapted behavior. All these processes measured by experimental or more integrated tasks are affected by wakefulness level. Thus, we need to 1) precise evaluation of performances inter-task differences in fully awake subject, 2) describe the evolution of theses performances inter-task differences when subject wakfulness level drop, 3) investigate interindividual differences in these performances evolutions.BORDEAUX2-BU Sci.Homme/Odontol. (330632102) / SudocSudocFranceF

Volume imaging of anisotropic materials

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Scalar approximation of Maxwell equations: derivation and accuracy

International audienceReplacing Maxwell equations by a scalar wave equation is often used in computational imaging to simulate the light-sample interaction. It significantly reduces the computational burden but provides field maps that are insensitive to the polarization of the incident field, provided the latter is constant throughout the sample. Here, we develop a scalar approximation that accounts for the polarization of the incident field. Comparisons with rigorous simulations show that this approach is more accurate than the classical scalar approximation with similar computational cost

Accelerating the discrete dipole approximation by initializing with a scalar solution and using a circulant preconditioning

The discrete dipole approximation (DDA) is a method of choice for simulating the electromagnetic scattering by objects of arbitrary shape and permittivity. To recover the field inside the object, it requires the iterative solving of a dense linear system which can be time consuming. To ease this task, we propose to start the inversion with the solution of the recently introduced scalar approximation [Chaumet et al. J. Opt. Soc. Am. A, 39 , 1462 (2022)]. This initial guess allows a reduction of the time required for the solving of the linear system up to 50%. In addition, we study the interest of preconditioning the system to accelerate convergence. We show that the gain can be up to a factor of 5, especially for homogeneous objects on a plane substrate

Diaphragmatic motion recorded by M-mode ultrasonography: limits of normality

International audienceChest ultrasonography has proven to be useful in the diagnosis of diaphragm dysfunction. The aim of the present study was to determine the normal values of the motion of both hemidiaphragms recorded by M-mode ultrasonography. Healthy volunteers were studied while in a seated position. Diaphragmatic excursions and diaphragm profiles were measured during quiet breathing, voluntary sniffing and deep breathing. Diaphragmatic excursions were assessed by M-mode ultrasonography, using an approach perpendicular to the posterior part of the diaphragm. Anatomical M-mode was used for the recording of the complete excursion during deep breathing. The study included 270 men and 140 women. The diaphragmatic motions during quiet breathing and voluntary sniffing were successfully recorded in all of the participants. The use of anatomical M-mode was particularly suitable for measurement of the entire diaphragmatic excursion during deep breathing. The statistical analysis showed that the diaphragmatic excursions were larger in men compared to women, supporting the determination of normal values based on sex. The lower and upper limits of normal excursion were determined for men and women for both hemidiaphragms during the three manoeuvres that were investigated. The lower limits of normal diaphragmatic excursions during deep breathing should be used to detect diaphragmatic hypokinesia, i.e. 3.3 and 3.2 cm in women and 4.1 and 4.2 cm in men for the right and the left sides, respectively. The normal values of the diaphragmatic motion and the lower and upper limits of normal excursion can be used by clinicians to detect diaphragmatic dysfunction