B016 Impact of a 14-night intermittent hypoxia (IH) exposure on metabolic and cardiopulmonary adaptations to exercise in healthy subjects

IntroductionModifications in exercise tolerance have been reported in obstructive sleep apnea (OSA) patients. Also specific mechanisms have been speculated related to intermittent hypoxia (IH), hypertension, obesity or metabolic disturbance associated to OSA may play a significant role in exercise limitation. In order to eliminate these confounding factors we aimed to evaluate the effects of IH exposure during 14 nights in healthy subjects on exercise capacity, cardio-respiratory response and substrate oxidation during exercise.Methods12 healthy subjects (BMI: 21.8 0.5kg.m-2) were exposed to repetitive sequences of hypoxia — re-oxygenation during sleep in a hypoxic tent with appropriate cyclic re-oxygenation (rate: 30 desaturations.h-1). Maximal and sub-maximal exercise tests were performed before and after exposure in order to investigate cardiorespiratory variables and substrate oxidation parameters.ResultsIH did not modify maximal exercise parameters (VO2, heart rate, power output) nor ventilatory threshold (VTh). But this was achieved with a significant PETCO2 reduction and a VE/VCO2 increase during both maximal (Pre IH vs Post IH at VTh and Max, p<0.05) and sub-maximal (Pre vs Post at 30 % and 60 % Pmax, p<0.05) exercise tests, indicating hyperventilation. At the 1st min recovery after submaximal exercise test, diastolic arterial blood pressure (DBP) was higher after IH exposure (Pre: 60±3 vs Post: 78±2mmHg) in favour of a delayed DBP recovery following acute exercise. During sub-maximal exercise, subjects reached maximal lipid oxidation at higher power output and presented a decreased blood lactate at the same percentage of relative power after IH exposure.ConclusionExposure to 14 days of nocturnal IH is associated with an increased ventilatory response to subsequent exercise at sea level. Furthermore, delayed DBP recovery after exercise is in favor of early IH-induced cardiovascular modifications. This observation related to muscular exercise adaptations confirms the efficacy of the model in reproducing early cardiovascular alterations occurring in OSAS. Moreover, this model induces metabolic adaptations as soon as 14 nights of exposure

Effets du dérangement par la chasse sur les oiseaux d'eau : revue de littérature

La chasse aux oiseaux d'eau, activité humaine largement pratiquée sur les zones humides du continent eurasiatique, présente deux composantes pouvant affecter la dynamique des populations de ces espèces migratrices : le prélèvement (qui concerne la mortalité) et le dérangement. Ce dernier aspect fait l'objet d'études de plus en plus nombreuses et détaillées, ici synthétisées, incluant des protocoles expérimentaux et des approches conceptuelles. Le dérangement par la chasse est considéré comme important pour une espèce lorsque les modifications qu'il induit ont un effet sur la « fitness » des individus de cette espèce (diminution de la survie et/ou du succès reproducteur). Les études montrent que le dérangement modifie presque toujours la distribution géographique des oiseaux en favorisant leur regroupement (5 à 50 fois plus) sur des espaces non chassés, induisant une sous-exploitation des ressources trophiques présentes sur les espaces chassés. Le dérangement peut aussi provoquer un accroissement du taux de renouvellement (« turnover ») des individus sur leur étape migratoire. Ces transferts d'oiseaux, bien quantifiés localement, ont un impact encore inconnu sur la taille des populations concernées, la large distribution de ces populations sur plusieurs continents rendant cette évaluation difficile. Le dérangement provoque une modification comportementale soit en favorisant des activités plus coûteuses que celles pratiquées sans dérangement, soit en diminuant le temps passé à des activités qui permettent d'acquérir de l'énergie. Les estimations ou simulations de ces pertes peuvent atteindre 25 % de la dépense énergétique journalière. Les oiseaux dérangés développent des capacités d'adaptation physiologique face aux contraintes associées au dérangement, par exemple une augmentation de la prise alimentaire, une augmentation du rendement de l'assimilation énergétique ou une augmentation de la sécrétion de corticostérone qui stimule l'activité de recherche de nourriture. L'évaluation directe du bilan énergétique de ces adaptations n'a pas encore été réalisée et l'on peut admettre qu'elles permettent à l'oiseau de maintenir un apport énergétique analogue à celui obtenu sans dérangement; mais le coût à terme de cette acquisition est élevé. Ainsi, une étude récente sur la Grande Oie des neiges Anser caerules-cens atlantica au Canada révèle que lorsque les individus sont dérangés par la chasse sur leur étape migratoire de printemps, ils sont contraints d'exploiter des sites moins riches que s'il n'y avait pas de chasse; ils sont alors dans de moins bonnes conditions corporelles (lipidiques et protéiniques) lors du départ vers leurs lieux de reproduction et ils ont finalement un moindre succès de reproduction que les individus n'ayant pas subi le dérangement par la chasse. Certes, des lacunes et des incertitudes persistent, par exemple au niveau spécifique (peu d'études sur les limicoles), mais tous les auteurs qui les ont mises en évidence s'accordent aussi pour reconnaître que, pour contrebalancer les effets du dérangement par la chasse, des mesures de protection doivent être prises.Waterbird hunting is a widespread human activity over wetlands of the Eurasian continent. It has two components that can influence the population dynamics of migratory species : mortality and disturbance. Disturbance is the focus of an increasing number of detailed studies, using both experimental and theoretical approaches. They are synthesized herein. Disturbance is considered important when induced changes influence the fitness of the individuals of a species (decrease in survival or breeding success). Studies show that disturbance almost always change the geographical distribution of birds, conducting to an under-exploitation of food resources available in hunting areas. Disturbance can also favour an increase in the turnover rate of individuals on their migratory stopover. These changes in bird distribution, although precisely quantified at a local scale, have an unknown impact on the population size of the concerned species. The wide distribution of several of these species ranging over several continents makes the precise evaluation of this impact difficult. Disturbance changes behaviour either by increasing time spent in activities more costly than those done without disturbance or by decreasing time spent gaining energy. Estimation or simulation of these lost can reach 25% of the daily energy expenses. Facing disturbance, birds can develop several physiological adaptations, for instance an increased food intake, an increased efficiency of energy assimilation or an augmentation of corticosterone secretion stimulating food searching. The direct evaluation of the energy balance of these adaptations has not been made yet and it can be acknowledged that they allow birds to maintain energy gains similar to those obtained without disturbance. However, the long-term cost of this compensation is high. A recent study of the Greater Snow Goose Anser caerulescens atlantica on their spring stopover in Canada indicates that hunting disturbance makes geese use lower quality habitats, decreases their body condition (fat and protein) when they depart to the breeding sites and decreases their breeding success relative to individuals that have not experienced hunting. Uncertainties remain, for instance at the species level (few studies on waders), but all authors that emphasized them also agree to acknowledge that protection measures must be taken to counter-balance the effects of hunting disturbance. They recommend the increase of protected areas (hunt-free areas), the elaboration of a network of reserves and the establishment of non hunted zones around existing reserves to reduce to the minimum the negative effects of disturbance on birds that use these reserves. The implementation of these management actions must favour the widening of the distribution of these populations and facilitate the local and regional increase of their numbers. These protection measures are positive responses to the recommendations of the European Union birds and habitats directives

Agreement in the scoring of respiratory events and sleep among international sleep centers.

To access publisher's full text version of this article. Please click on the hyperlink in Additional Links field.Abstract STUDY OBJECTIVES: The American Academy of Sleep Medicine (AASM) guidelines for polysomnography (PSG) scoring are increasingly being adopted worldwide, but the agreement among international centers in scoring respiratory events and sleep stages using these guidelines is unknown. We sought to determine the interrater agreement of PSG scoring among international sleep centers. DESIGN: Prospective study of interrater agreement of PSG scoring. SETTING: Nine center-members of the Sleep Apnea Genetics International Consortium (SAGIC). MEASUREMENTS AND RESULTS: Fifteen previously recorded deidentified PSGs, in European Data Format, were scored by an experienced technologist at each site after they were imported into the locally used analysis software. Each 30-sec epoch was manually scored for sleep stage, arousals, apneas, and hypopneas using the AASM recommended criteria. The computer-derived oxygen desaturation index (ODI) was also recorded. The primary outcome for analysis was the intraclass correlation coefficient (ICC) of the apnea-hypopnea index (AHI). The ICCs of the respiratory variables were: AHI = 0.95 (95% confidence interval: 0.91-0.98), total apneas = 0.77 (0.56-0.87), total hypopneas = 0.80 (0.66-0.91), and ODI = 0.97 (0.93-0.99). The kappa statistics for sleep stages were: wake = 0.78 (0.77-0.79), nonrapid eye movement = 0.77 (0.76-0.78), N1 = 0.31 (0.30-0.32), N2 = 0.60 (0.59-0.61), N3 = 0.67 (0.65-0.69), and rapid eye movement = 0.78 (0.77-0.79). The ICC of the arousal index was 0.68 (0.50-0.85). CONCLUSION: There is strong agreement in the scoring of respiratory events among the SAGIC centers. There is also substantial epoch-by-epoch agreement in scoring sleep variables. Our results suggest that centralized scoring of PSGs may not be necessary in future research collaboration among international sites where experienced, well-trained scorers are involved.NHLBI P01 HL094307 HL093463 Tzagournis Medical Research Endowment Funds of The Ohio State Universit

Acute Feasibility of Neuromuscular Electrical Stimulation in Severely Obese Patients with Obstructive Sleep Apnea Syndrome: A Pilot Study

Objective. Obesity and obstructive sleep apnea (OSA) are closely interconnected conditions both leading to high cardiovascular risk. Inactivity is frequent and physical activity programs remain difficult in these patients. We investigated the acute feasibility of two neuromuscular electrical stimulation (NMES) modalities in extremely inactive obese patients with OSA. Design. A randomized cross-over study, with two experimental sessions (one per condition: multipath NMES versus conventional NMES). Setting. Outpatient research hospital. Subjects. Twelve patients with obesity, already treated for OSA. Interventions. No intervention. Measures. Feasibility outcomes included NMES current intensity, knee extension force evoked by NMES, and self-reported discomfort. Results. We found higher current intensity, a trend to significantly higher evoked force and lower discomfort during multipath NMES versus conventional NMES, suggesting better tolerance to the former NMES modality. However, patients were rapidly limited in the potential of increasing current intensity of multipath NMES. Conclusion. Both NMES modalities were feasible and relatively well tolerated by obese patients with OSA, even if multipath NMES showed a better muscle response/discomfort ratio than conventional NMES. There is an urgent need for a proof-of-concept study and interventional randomized controlled trials comparing NMES therapy versus current care to justify its utilization in obese and apneic patients with low physical activity levels

Is Mate Choice in Humans MHC-Dependent?

In several species, including rodents and fish, it has been shown that the Major Histocompatibility Complex (MHC) influences mating preferences and, in some cases, that this may be mediated by preferences based on body odour. In humans, the picture has been less clear. Several studies have reported a tendency for humans to prefer MHC-dissimilar mates, a sexual selection that would favour the production of MHC-heterozygous offspring, who would be more resistant to pathogens, but these results are unsupported by other studies. Here, we report analyses of genome-wide genotype data (from the HapMap II dataset) and HLA types in African and European American couples to test whether humans tend to choose MHC-dissimilar mates. In order to distinguish MHC-specific effects from genome-wide effects, the pattern of similarity in the MHC region is compared to the pattern in the rest of the genome. African spouses show no significant pattern of similarity/dissimilarity across the MHC region (relatedness coefficient, R = 0.015, p = 0.23), whereas across the genome, they are more similar than random pairs of individuals (genome-wide R = 0.00185, p<10−3). We discuss several explanations for these observations, including demographic effects. On the other hand, the sampled European American couples are significantly more MHC-dissimilar than random pairs of individuals (R = −0.043, p = 0.015), and this pattern of dissimilarity is extreme when compared to the rest of the genome, both globally (genome-wide R = −0.00016, p = 0.739) and when broken into windows having the same length and recombination rate as the MHC (only nine genomic regions exhibit a higher level of genetic dissimilarity between spouses than does the MHC). This study thus supports the hypothesis that the MHC influences mate choice in some human populations

Enhanced Migratory Waterfowl Distribution Modeling by Inclusion of Depth to Water Table Data

In addition to being used as a tool for ecological understanding, management and conservation of migratory waterfowl rely heavily on distribution models; yet these models have poor accuracy when compared to models of other bird groups. The goal of this study is to offer methods to enhance our ability to accurately model the spatial distributions of six migratory waterfowl species. This goal is accomplished by creating models based on species-specific annual cycles and introducing a depth to water table (DWT) data set. The DWT data set, a wetland proxy, is a simulated long-term measure of the point either at or below the surface where climate and geological/topographic water fluxes balance. For species occurrences, the USGS' banding bird data for six relatively common species was used. Distribution models are constructed using Random Forest and MaxEnt. Random Forest classification of habitat and non-habitat provided a measure of DWT variable importance, which indicated that DWT is as important, and often more important, to model accuracy as temperature, precipitation, elevation, and an alternative wetland measure. MaxEnt models that included DWT in addition to traditional predictor variables had a considerable increase in classification accuracy. Also, MaxEnt models created with DWT often had higher accuracy when compared with models created with an alternative measure of wetland habitat. By comparing maps of predicted probability of occurrence and response curves, it is possible to explore how different species respond to water table depth and how a species responds in different seasons. The results of this analysis also illustrate that, as expected, all waterfowl species are tightly affiliated with shallow water table habitat. However, this study illustrates that the intensity of affiliation is not constant between seasons for a species, nor is it consistent between species

Upper airway dynamics during negative expiratory pressure in apneic and non-apneic awake snorers

BACKGROUND: The ability of negative expiratory pressure (NEP) technique to differentiate between awake snorers with and without obstructive sleep apnea-hypopnea (OSAH) was investigated. METHODS: Forty-eight subjects with sleep disordered breathing (SDB) and 7 healthy subjects, as non-snorer controls, underwent the NEP application of -5 and -7 cmH(2)O in the seated and supine position during wakefulness, after performing a sleep study. The upper airway collapsibility was assessed by computing the volume exhaled during the first 0.5 sec. (V,NEP(0.5)) and 1 sec. (V,NEP(1)) following the NEP start. RESULTS: Patients with severe (AHI ≥ 30) (n = 19) and mild-to-moderate (AHI <30 and >5) (n = 15) OSAH had lower V,NEP(0.5 )(340 ± 88 ml) as compared to snorers (AHI ≤ 5) (n = 14) (427 ± 101 ml; p < 0.01) and controls (n = 7) (492 ± 69 ml; p < 0.001) in the supine position with NEP -5 cmH(2)O. Less significant differences among the different groups were observed for V,NEP(0.5 )in the seated position with NEP -5 cmH(2)O and in both positions with NEP -7 cmH(2)O (only OSAH patients vs controls, p < 0.001). Similar results were obtained for V,NEP(1 )in either position by using both NEP -5 cmH(2)O and -7 cmH(2)O. In spite of this, a substantial overlapping of V,NEP(0.5 )and V,NEP(1 )between snorers and OSAH patients did not allow to identify a reliable diagnostic cut-off level. An inverse correlation with AHI was found for V,NEP(0.5 )in the supine position with NEP -5 cmH(2)O (r(s )= -0.46, p < 0.05) in severe OSAH patients. CONCLUSION: The awake OSAH patients exhibit values of V,NEP(0.5 )and V,NEP(1 )lesser than those of awake snorers. The NEP technique, however, appears to have a limited usefulness as clinical tool for routine screening of the OSAH patients during wakefulness

Effect of mandibular advancement therapy on inflammatory and metabolic biomarkers in patients with severe obstructive sleep apnoea: a randomised controlled trialTrial registration number

Systemic inflammation and metabolic disorders are among the mechanisms linking obstructive sleep apnoea (OSA) and cardiovascular disease (CVD). In 109 patients with severe OSA and no overt CVD, biomarkers of inflammation (C reactive protein, interleukin-6, tumour necrosis factor-α and its receptors, adiponectin, leptin and P-selectin), glucose and lipid metabolism, and N-terminal pro-brain natriuretic peptide, were measured before and after 2 months of treatment with a mandibular advancement device (MAD) (n=55) or a sham device (n=54). MAD reduced the Apnoea–Hypopnoea Index (p&lt;0.001) but had no effect on circulating biomarkers compared with the sham device, despite high treatment adherence (6.6 hour/night)

Spread of Avian Influenza Viruses by Common Teal (Anas crecca) in Europe

Since the recent spread of highly pathogenic (HP) H5N1 subtypes, avian influenza virus (AIV) dispersal has become an increasing focus of research. As for any other bird-borne pathogen, dispersal of these viruses is related to local and migratory movements of their hosts. In this study, we investigated potential AIV spread by Common Teal (Anas crecca) from the Camargue area, in the South of France, across Europe. Based on bird-ring recoveries, local duck population sizes and prevalence of infection with these viruses, we built an individual-based spatially explicit model describing bird movements, both locally (between wintering areas) and at the flyway scale. We investigated the effects of viral excretion duration and inactivation rate in water by simulating AIV spread with varying values for these two parameters. The results indicate that an efficient AIV dispersal in space is possible only for excretion durations longer than 7 days. Virus inactivation rate in the environment appears as a key parameter in the model because it allows local persistence of AIV over several months, the interval between two migratory periods. Virus persistence in water thus represents an important component of contamination risk as ducks migrate along their flyway. Based on the present modelling exercise, we also argue that HP H5N1 AIV is unlikely to be efficiently spread by Common Teal dispersal only