Purpose Underwater divers face several potential neurological hazards when breathing compressed gas mixtures including nitrogen narcosis which can impact diver's safety. Various human studies have clearly demonstrated brain impairment due to nitrogen narcosis in divers at 4 ATA using critical flicker fusion frequency (CFFF) as a cortical performance indicator. However, recently some authors have proposed a probable adaptive phenomenon during repetitive exposure to high nitrogen pressure in rats, where they found a reversal effect on dopamine release. Methods Sixty experienced divers breathing Air, Trimix or Heliox, were studied during an open water dive to a depth of 6 ATA with a square profile testing CFFF measurement before (T 0 ), during the dive upon arriving at the bottom (6 ATA) (T 1 ), 20 min of bottom time (T 2 ), and at 5 m (1.5 ATA) (T 3 ). Results CFFF results showed a slight increase in alertness and arousal during the deep dive regardless of the gas mixture breathed. The percent change in CFFF values at T 1 and T 2 differed among the three groups being lower in the air group than in the other groups. All CFFF values returned to basal values 5 min before the final ascent at 5 m (T 3 ), but the Trimix measurements were still slightly better than those at T 0 . Conclusions Our results highlight that nitrogen and oxygen alone and in combination can produce neuronal excitability or depression in a dose-related response. Keywords Nitrogen narcosis • Divers' safety • Critical flicker fusion frequency • GABA receptors Abbreviations ATA Atmospheres of pressure absolute 1 ATA = 1.01325 bar, 760 mmHg, 10 m H 2 O CFFF Critical flicker fusion frequency DCS Decompression sickness EAN Enriched air nitrox GABA receptors Gamma aminobutyric acid receptors HELIOX Helium and oxygen HPNS High pressure nervous syndrome TRIMIX Mixture of nitrogen, helium and oxygen Communicated by Jean-René Lacour.

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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide causing a global pandemic. In this context, lung ultrasound (LUS) has played an important role due to its high diagnostic sensitivity, low costs, simplicity of execution and radiation safeness. Despite computed tomography (CT) being the imaging gold standard, lung ultrasound point of care exam is essential in every situation where CT is not readily available nor applicable. The aim of our review is to highlight the considerable versatility of LUS in diagnosis, framing the therapeutic route and follow-up for SARS-CoV-2 interstitial syndrome.

Background. Fourteen adults undergoing tracheal resection and reconstruction surgery were enrolled in this prospective observational pilot study to evaluate dexmedetomidine-based sedation after tracheal surgery in an intensive care unit.Methods. Patients remained electively intubated with an uncuffed nasal endotracheal tube, awake and exhibiting spontaneous breathing. The neck was maintained in flexion through chin-to-chest sutures. Infusion of dexmedetomidine was started from a dosage of 0.7 mg $ kg -1 $ h -1 followed by dose titration to the target level of the sedation Richmond Agitation Sedation Scale (RASS) score -1 to -2 using a dose range of 0.2 to 1.4 mg $ kg -1 $ h -1 .

Introduction: Decompression sickness (DCS) is considered a ‘bubble disease’. Intravascular bubbles activate inflammatory responses associated with endothelial dysfunction. Breathing gas has been proposed as a potential risk factor but this is inadequately studied. Different gases are used in scuba diving. Helium-containing 'trimix' could theoretically mitigate inflammation and therefore reduce DCS risk. This study determined the effect of air and trimix on the inflammatory response following dives to 50 metres of sea water, and evaluated the differences between them in advanced recreational divers. Methods: Thirty-three divers were enrolled in this observational study and were divided in two groups: 17 subjects were included in the air group, and 16 different subjects were included in the trimix (21% oxygen, 35% helium, 44% nitrogen) group. Each subject conducted a single dive, and both groups used a similar diving profile of identical duration. A venous blood sample was taken 30 min before diving and 2 h after surfacing to evaluate changes in interleukins (IL) IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor α (TNFα), vascular endothelial growth factor (VEGF), Interferon γ (IFN-γ), monocyte chemoattractant protein 1 (MCP-1) and epithelial growth factor (EGF) after diving. Results: No differences were observed between groups in demographic data or diving experience. Following the dive, IL-6 values showed a slight increase, while IL-8 and EGF decreased in both groups, without significant variation between the groups. Conclusions: In physically fit divers, trimix and air gas mixture during deep diving did not cause relevant changes in the inflammatory markers tested.