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

Caractérisation acoustique de conduits auditifs externes normaux : de l’humain aux modèles imprimés 3D

Objectif : Créer et valider un modèle de CAE normal par impression en 3D bio-fidèles aux CAE humains. Méthodologie : Nous avons prélevé dix CAE humains sur des pièces anatomiques. Après acquisition volumique sur un scanner conventionnel, la conception numérique des CAE en 3D comportait une segmentation et la mise en place d’un support tympanique. Nous avons utilisé du PLA pour l’impression et du ruban adhésif pour simuler une MT artificielle. La vélocimétrie de l’umbo a été mesurée au moyen d’un laser couplé à une chaine acoustique de stimulation-recueil dédiée. Résultats : Comparés aux CAE humains, les modèles ont montré des réponses identiques statistiquement. Un second pic était observé à 5 kHz sur le pattern des CAE imprimés. Les hautes fréquences montraient un profil plus chaotique. Conclusion : Les CAE imprimés en 3D sont des modèles valides et bio-fidèles aux CAE humains. La normalisation des amplifications observées permet d’obtenir un modèle utile pour l’optimisation des dispositifs d’amplification ou de protection auditifs