Gaz respiratoire | EPFL Graph Search

Un gaz respirable est un mélange d'éléments chimiques gazeux et de composés utilisés pour la respiration. L'air est le gaz respiratoire le plus courant et naturel, mais une gamme de gaz purs ou de mélanges de gaz sont utilisés dans les équipements de respiration et les habitats clos comme l'équipement de plongée sous-marine, l'équipement de plongée fourni par la surface, les chambres de recompression, les sous-marins, les costumes spatiaux, les engins spatiaux, le support médical de la vie et l'équipement de premiers soins, l'alpinisme de haute altitude et les machines d'anesthésie. L'oxygène est la composante essentielle pour tout gaz respiratoire, à une pression partielle entre environ 0,16 et à la pression ambiante. L'oxygène est habituellement le seul composant métaboliquement actif à moins que le gaz soit un mélange anesthésique. Une partie de l'oxygène dans le gaz respiratoire est consommée par les processus métaboliques, et les composants inertes sont inchangés, et servent pr

Motor state transitions and Breathing in Brain Machine Interfaces

Bastien Orset

Brain-Machine interfaces aim to create a direct neural link between user's brain and machines. This goal has pushed scientists to investigate a large spectrum of applications in the realm of assistive and rehabilitation technologies. However, despite great progress, the possibility of being in full control of a device with our brain is still far to be reached. One of the primary limitations of BMIs is the notion of self-paced control, which states that a user should be able to activate or deactivate such interface by mere modulation of brain activity. Many studies have investigated this question, focusing notably on the use of endogenous signals (such as Event-Related Desynchronization/Synchronization, ERD/S) to control the activation of these interfaces in natural interaction scenarios. This question is, however, largely ignored when looking at their interruption. Hence, in this first part of the thesis, my work was devoted to investigate how a BMI user would be able to control the interruption of non-invasive BMIs based on Motor Imagery (MI), a paradigm promoting natural and endogenous signals that can be used for BMI control. I investigated the decoding of motor termination as well as its correlates characterized by the post-movement ERS phenomenon. Specifically, this part of the thesis aimed to study (i) the feasibility to decode motor termination from a specific neural correlate as well as the adaptation from the user in closed-loop scenarios, (ii) the benefits of using motor termination correlates to detect the stopping process, and (iii) the effect of BMI effectors such as an exoskeleton on the detection of motor termination correlates. The obtained results provide new insights into closed-loop decoding of motor termination. In particular, I show that BMI users exhibit an adaptation of their EEG correlates enabling them to have a reliable control when switching off a BMI in closed-loop scenarios. Second, I show that the decoding of motor termination is a particular process different from a resting state and, hence, should be decoded independently so as to achieve a faster and more robust detection. Finally, I investigate the use of BMI effectors with respect to the decoding of motor termination showing an effect of the effectors on the correlates of motor termination. However, due to the nature of these correlates, motor termination can still be reliably decoded with a similar latency. In the second part of my thesis, I also investigate how the interoceptive system affects BMI and particularly how breathing signals affect BMI based on MI. Breathing has been shown to have a key effect on numerous human functions, including, perceptual, cognitive and motor functions. However, currently not much is known about the role of respiratory signals in BMI and such signals have rather been considered as physiological noise. In my thesis, I evaluated how the breathing process affects the correlates of MI (ERD in mu and beta bands) as well as actual BMI performance. The results provide an extensive analysis regarding the effect of the breathing cycle specifically on mu-ERDs, showing stronger ERD during the late expiration phase. Moreover, I identified a link between breathing and BMI performance and propose that breathing signals are a valuable predictor for BMI performance highlighting the importance of monitoring such signals and, more generally, present the interoceptive system as a key component of motor preparation and motor imagery

EPFL2021

Heterogeneous Chemistry of Cl2O and HOCl on Frozen Natural Sea Salt, Recrystallized Sea Salt, KCl and NaCl Solutions at 200 and 215 K

Pascal Pratte, Michel Rossi

The HOCl heterogeneous reaction on frozen natural (NSS) and recrystallized (RSS) sea salt KCl and NaCl solutions was studied using a low pressure flow reactor in order to measure the uptake coefficient gamma and products of reaction The HOCl sample used in these experiments always contained up to 25% Cl2O which was also studied separately as a pure gas in order to understand the heterogeneous chemistry of both gases By performing HOCl uptake on frozen NSS solution at 200 K and a gas phase residence time of (1 6 +/- 0 6) s we obtained a steady state uptake coefficient gamma(HOCl) (on NSS) = (2 5 +/- 0 7) X 10(-3) and gamma(Cl2O on NSS) = (2 8 +/- 0 8) X 10(-3) On frozen KCl solution at 200 K we obtain gamma(HOCl on KCl) = (2 8 +/- 1 3) X 10(-3) identical to NSS and gamma(Cl2O on) (KCl) = (4 6 +/- 0 8) X 10(-4) The main product formed during the uptake, on frozen NSS solution is Cl-2 which is sustained for at least one hour In contrast only a transient Cl-2 flow (pulse) decreasing on the time scale of 100 s was observed on frozen KCl (NaCl) solution 25 +/- 10 % of the HOCl taken up on all chloride containing frozen substrates at 200 K react to produce Cl-2 at high HOCl concentration (4 5 X 10(11) molecule cm(-3)) and at a residence time of 1 6 s in comparison with twice that for Cl2O For smaller concentrations such as [HOCl] = 3 7 X 10(10) molecule cm(-3) and/or a shorter residence time (0 137 +/- 0 004s) HOCl uptake did not generate Cl-2 in contrast to Cl2O A single Br-2 burst event was monitored when a Cl2O or HOCl/Cl2O mixture is taken up on fresh frozen NSS solution during the first uptake at 200 K Further Cl2O or HOCl/Cl2O uptake on the same sample even after annealing at 240 K does not show an additional Br-2 pulse This Br-2 release may be significant in the autocatalytic ozone destruction mechanism in the troposphere during polar sunrise Some of the atmospheric implications of the present results are highlighted with emphasis on the preequilibrium Cl2O(ads) + H2O(ice) reversible arrow 2 HOCl(ads) between adsorbed HOCl and Cl2O with the latter being the gateway to reactive uptake of HOCl at low temperatures

Oldenbourg Wissenschaftsverlag GmbH, De Gruyter2010

Altered cerebrovascular reactivity velocity in mild cognitive impairment and Alzheimer's disease

Sven Haller, Jonas Richiardi, Dimitri Nestor Alice Van De Ville

Interindividual variation in neurovascular reserve and its relationship with cognitive performance is not well understood in imaging in neurodegeneration. We assessed the neurovascular reserve in amnestic mild cognitive impairment (aMCI) and Alzheimer's dementia (AD). Twenty-eight healthy controls (HC), 15 aMCI, and 20 AD patients underwent blood oxygen level-dependent imaging for 9 minutes, breathing alternatively air and 7% carbon dioxide mixture. The data were parcellated into 88 anatomic regions, and carbon dioxide regressors accounting for different washin and washout velocities were fitted to regional average blood oxygen leveledependent signals. Velocity of cerebrovascular reactivity (CVR) was analyzed and correlated with cognitive scores. aMCI and AD patients had significantly slower response than HC (mean time to reach 90% of peak: HC 33 seconds, aMCI and AD 59 seconds). CVR velocity correlated with Mini Mental State Examination in 35 of 88 brain regions (p = 0.019, corrected for multiple comparisons), including 10 regions of the default-mode network, an effect modulated by age. This easily applicable protocol yielded a practical assessment of CVR in cognitive decline. (C) 2015 Elsevier Inc. All rights reserved.