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

Editorial: Training, performance and rehabilitation in water-based sports

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Editorial: Physiology and Physiopathology of Breath-Holding Activity

International audienceResearch into voluntary apnea is becoming increasingly popular in varied laboratories and in the field around the world. In the last 10 years, as many articles have been published than between 1954 and 2011. Breath-hold diving is truly an antique practice; for example, Alexandre Legrand employed professional breath hold divers called “Urinator” in his army, and Japanese Ama and Philippine Bajau people have been known to dive for hundreds of years to gather food. More recently, apnea diving became a high-level competitive sport with impressive performances (e.g., world record for static apnea of 11 mins 35 s and for depth No-Limit diving −214 m), but although constant progress is made, human performance is still far from the prowess of marine mammals (e.g., Ziphius cavirostris, apnea duration: 137 mins and 2,992 m depths). Despite major anatomical and physiological differences between humans and marine mammals, humans present with an interesting physiological response to apnea to limit the effects of hypoxia and/or pressure increase, in which the main physiological functions such as pulmonary, cardiovascular, and nervous functions can be modulated acutely and chronically. The Research Topic focuses on these varied facets but also their trainability and their consequences on health in relation to some hypoxia-related pathologies such as sleep apnea syndrome, pulmonary edema and decompression sickness

Apnea: A new training method in sport?

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Modeling the diving bradycardia: Toward an “oxygen-conserving breaking point”?

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Exponential Relationship Between Maximal Apnea Duration and Exercise Intensity in Non-apnea Trained Individuals

International audienceIt is well known that the duration of apnea is longer in static than in dynamic conditions, but the impact of exercise intensity on the apnea duration needs to be investigated. The aim of this study was to determine the relationship between apnea duration and exercise intensity, and the associated metabolic parameters. Ten healthy active young non-apnea trained (NAT) men participated in this study. During the first visit, they carried out a maximum static apnea (SA) and a maximal progressive cycle exercise to evaluate the power output achieved at peak oxygen uptake (PVO 2 peak). During the second visit, they performed four randomized dynamic apneas (DAs) at 20, 30, 40, and 50% of PVO 2 peak (P20, P30, P40, and P50) preceded by 4 min of exercise without apnea. Duration of apnea, heart rate (HR), arterial oxygen saturation (SpO 2 ), blood lactate concentration [La], rating of perceived exertion (RPE), and subjective feeling were recorded. Apnea duration was significantly higher during SA (68.1 ± 23.6 s) compared with DA. Apnea duration at P20 (35.6 ± 11.7 s) was higher compared with P30 (25.6 ± 6.3 s), P40 (19.2 ± 6.7 s), and P50 (16.9 ± 2.5 s). The relationship between apnea duration and exercise intensity followed an exponential function ( y = 56.388e –0.025 x ). SA as DA performed at P20 and P30 induces a bradycardia. Apnea induces an SpO 2 decrease which is higher during DA (−10%) compared with SA (−4.4%). The decreases of SPO 2 recorded during DA do not differ despite the increase in exercise intensity. An increase of [La] was observed in P30 and P40 conditions. RPE and subjective feeling remained unchanged whatever the apnea conditions might be. These results suggest that the DA performed at 30% of VO 2 peak could be the best compromise between apnea duration and exercise intensity. Then, DA training at low intensity could be added to aerobic training since, despite the moderate hypoxia, it is sufficient to induce and increase [La] generally observed during high-intensity training

Underwater and Surface Swimming Parameters Reflect Performance Level in Elite Swimmers

International audienceAlthough the role of underwater phases is well-known, no study has taken an interest in describing and quantifying the distance and time spent in apnea as a condition for optimal performance. This study aimed to investigate the impact of time and distance spent underwater and surface parameters on the swimming performance of elite swimmers. The performances of 79 swimmers in 100-m freestyle were analyzed (short-course). The underwater and spatiotemporal parameters of three groups have been recorded: finalists of the 2018 World Swimming Championships (WORLD), French swimmers who reached a 100 m performance time under 50 s at the 2018 French National Championships (UND50), and those who reached a 100 m performance time above 50 s (UP50). The WORLD group spent more distance underwater (37.50 ± 4.92 m) in comparison with UND50 (31.90 ± 4.88 m, p < 0.05) and UP50 (31.94 ± 4.93 m, p < 0.01) groups. The total percentage of non-swimming time was higher for WORLD (39.11 ± 4.73%) vs. UND50 (34.21 ± 4.55%, p < 0.05) and UP50 (33.94 ± 5.00%, p < 0.01). In addition, underwater speed was higher for WORLD (2.54 ± 0.05 m/s) compared with UND50 (2.46 ± 0.09 m/s, p < 0.05) and UP50 (2.38 ± 0.11 m/s, p < 0.01). Three parameters among the underwater phases (i.e. distance underwater, speed underwater, and total percentage of non-swimming time) determine the 100-m freestyle short course performance. These data suggest an appropriate focus on specific apnea training to improve underwater skills during short-course swimming performances

Post-synthetic modification of Prussian blue type nanoparticles: tailoring the chemical and physical properties

International audiencePrussian blue (PB) type nanoparticles belong to an exciting family of molecule-based nanomaterials. They combine the possibility of surface engineering with specific advantages related to their porous molecule-based structures and their fascinating chemical and physical properties including redox, magnetic, photothermal and host–guest features. In this review, we focus on recent advances in the Post-Synthetic Modification (PSM) of nano-sized PB and its analogues (PBA) and compare them with the current strategies used in Metal–Organic Frameworks (MOF) in order to give the outlooks on the future researches in this domain

Static Apnea Effect on Heart Rate and Its Variability in Elite Breath-Hold Divers

International audienceBackground: The diving response includes cardiovascular adjustments known to decrease oxygen uptake and thus prolong apnea duration. As this diving response is in part characterized by a pronounced decrease in heart rate (HR), it is thought to be vagally mediated.Methods: In five professional breath-hold divers (BHDs) and fi ve less-trained controls (CTL), we investigated whether the diving response is in fact associated with an increase in the root mean square successive difference of the R-R intervals (RMSSD), a time-domain heart rate variability (HRV) index. HR behavior and arterial oxygen saturation (S a O 2) were continuously recorded during one maximal apnea. Short-term changes in S a O 2 , HR, and RMSSD were calculated over the complete apnea duration.Results: BHDs presented bi-phasic HR kinetics, with two HR decreases (32 6 17% and 20 6 10% of initial HR). The second HR decrease, which was concomitant to the pronounced S a O 2 decrease, was also simultaneous to a marked increase in RMSSD. CTL showed only one HR decrease (50 6 10% of initial HR), which appeared before the concomitant S a O 2 and RMSSD changes. When all subject data were combined, arterial desaturation was positively correlated with total apnea time (r 5 0.87, P , 0.01).Conclusion: This study indicates that barorefl ex stimulation and hypoxia may be involved in the bi-phasic HR response of BHDs and thus in their longer apnea duration

A Switch in the Hydrophobic/Hydrophilic Gas‐Adsorption Character of Prussian Blue Analogues: An Affinity Control for Smart Gas Sorption

International audiencePorous coordination polymers are molecule-based materials presenting a high degree of tunability, which offer many advantages for targeted applications over conventional inorganic materials. We demonstrate here that the hydrophilic-hydrophobic character of Prussian blue analogues having a lipophilic feature may be tuned to optimize the gas adsorption properties. The role of the coordinatively unsaturated metal sites is emphasized through a combination of theoretical and experimental study of water, ethanol and n-hexane adsorption. Porous coordination polymers are exciting molecule-based materials, made of metal ion nodes and molecular building blocks, which have attracted a great deal of attention for several decades not only from the fundamental point of view, but also due to potential technological applications in several fields including catalysis, gas storage, separation and purification. The most explored families of porous coordination polymers belong to Metal Organic Frameworks (MOFs) [1,2] and Prussian Blue Analogues (PBA) [3] have been investigated as promising alternatives for activated carbon or zeolite materials usually used in industry for gas storage [4] or separation/purification processes. [5-7] They present many advantages in comparison with conventional inorganic porous adsorbers consisting in: (i) "soft" chemistry routes for their synthesis, (ii) thermal and hydrothermal stability, (iii) comparable or higher adsorption capacities, (iv) structural flexibility providing the possibility to easily adjust the pore size and topology, (v) adjustable chemical composition permitting to optimize the physico-chemical properties of adsorption sites, such as the Coordination Unsaturated Sites (CUS), (vi) functionalization ability offering the possibility to tune the affinity between the host network and the guest molecules. [3,8] In particular, the adjustability of the hydrophobic/hydrophilic character of these materials, independently to their lipophilic/lipophobic balance, to finely adapt the interaction between guest molecules and host frameworks by using different approaches appears as a fundamental point for optimizing the adsorption properties. [9,10] In the targeted applications where adsorption is the main process, the surface chemistry of materials is indeed of prime importance. [11] In the case of MOFs, several strategies have been undertaken in order to adapt the affinity of the host network either for favouring or disfavouring interactions with sorbates: (i) the post-synthetic [12-14] or in-situ [15-17] functionalization of the framework, (ii) the modification of the CUS nature or their saturation to prevent strong interactions between metal center and sorbate molecules, [18] or (iii) the introduction of extra-framework charges by using for instance hydrophilic alkali or hydrophobic organic cations. [19], [20] In all these cases, the hydrophobic/hydrophilic character of the network is governed by the nature of the organic functionalities, metal ions, CUS, which modify the hydrophilic-hydrophobic balance by varying the nature of the interactions (strong covalent interactions, electrostatic or van der Waals interactions, H-bond interactions and hydrophobic interactions) of the solid network with guest species. Thus, in general cases, such modification of the hydrophobic/hydrophilic character is irreversible, except for MIL-53, which offers a hydrophobic-hydrophilic transition originating from a structural phase transition. Indeed the network is hydrophobic in the large pores form and becomes hydrophilic when water enters in the structure for the narrow pores form. [21][22] In contrast, PBA have been much less investigated for gas adsorption [23] despite an excellent hydrothermal stability and high adsorption capacities observed for the adsorption of water [24,25] , CO2 [26-28] or ammonia. [29] In this frame, Kawamoto et al highlighted the potential of PBAs for gas storage using different strategies, but to the best of our knowledge, their surface properties, in terms of hydrophobicity and hydrophilic character have never really been clarified up to now. [24] Recently, we reported on a series of lipophilic PBA materials, highly efficient for the separation of different vapors, such as water and hydrocarbons. [25] It was demonstrated that among this series of compounds, the Co[Co III (CN)6]0.66 PBA exhibits an important hydrothermal stability and a high adsorption capacity allowing it to be greatly efficient for the hydrocarbons separation in both, dry or humid atmospheres. In the present communication, we demonstrate for the first time the ability of this lipophilic Co[Co III (CN)6]0.66 PBA to reversibly switch its hydrophobic-hydrophilic character by coordination of water molecules on the CUS and optimize then its affinity for adsorption of molecules with different character, such as ethanol and n-hexane in humid and dry atmospheres. The PBA Co(H2O)x[Co III (CN)6]0.66•yH2O (x + y = 5.2 as determined by thermogravimetric analysis (Figure S1, Electronic Supporting Information (ESI)) 1 was obtained using the usual self-assembly reactions (see ESI). Figure 1 shows the fcc crystallographic structure of 1, where the Co 2+ and Co 3+ ions are connected through the cyano-bridge forming a 3D cubic structure with pores of ca. 0.5 nm. The electroneutrality in the structure is ensured by [Co III (CN)6] 3 vacancies, which generate randoml