The conundrum of using hyperoxia in COVID-19 treatment strategies: may intermittent therapeutic hyperoxia play a helpful role in the expression of the surface receptors ACE2 and Furin in lung tissue via triggering of HIF-1α?

In the current pandemic of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), the therapeutic administration of oxygen is a common procedure in order to mitigate patient’s hypoxia in the course of severe corona virus disease 2019 (COVID-19) pneumonia. However, additional oxygen causes a variety of well-known side-effects, impacting a number of systems regulating cardiovascular and respiratory homeostasis as well as reactive oxygen species (ROS)-production via oxidative stress. In this article, we want to focus on intermittent changes in lung and tissue oxygenation, as changes in local pO2 may be able to trigger one of the key effectors of cellular oxygen-sensing, hypoxia-inducible factor-1α (HIF-1α) and, in downstream, the expression of angiotensin-converting enzyme-2 (ACE2) and Furin

Correction to: Diving ergospirometry with suspended weights: breathing- and fin-swimming style matter

Purpose Scuba diving is a complex condition including elevated ambient pressure, limited air supply, increased breathing work, and unfamiliar fin-swimming. Earlier approaches to assess diving specific data did not comprehensively address these aspects. We first present an underwater ergospirometry system and then test the hypothesis that both breathing characteristics and fin-swimming style affect the air consumption. Results Ergo group: linear heart rate and oxygen uptake ([Formula: see text]O2) increases with both 50 W-bicycle steps and suspended-weights ergometry (r = 0.97). During hyperbaric conditions, [Formula: see text]E was less increased versus normobaric conditions. Style group: the more efficient hip/thigh-oriented style shifted towards the knee/calf-oriented style. [Formula: see text]E and [Formula: see text]O2 were higher in beginners (< 100 dives) versus advanced divers (≥ 100 dives). Significant differences on the 5 kg-step: [Formula: see text]E: 31.5 ± 7.1 l/min vs. 23.7 ± 5.9 l/min and [Formula: see text]O2: 1.6 ± 0.3 l/min vs. 1.2 ± 0.3 l/min. A comparison is presented, in addition to illustrate the impact of differences in breathing characteristics and fin-swimming style. Conclusions Diving ergospirometry with suspended weights in a hyperbaric chamber allows for comprehensive studies. Little diving experience in terms of breathing characteristics and fin-swimming style significantly increases [Formula: see text]E thereby increasing the risk of running-out-of-air

Diving ergospirometry with suspended weights: breathing- and fin-swimming style matter

Purpose Scuba diving is a complex condition including elevated ambient pressure, limited air supply, increased breathing work, and unfamiliar fin-swimming. Earlier approaches to assess diving specific data did not comprehensively address these aspects. We first present an underwater ergospirometry system and then test the hypothesis that both breathing characteristics and fin-swimming style affect the air consumption. Results Ergo group: linear heart rate and oxygen uptake ([Formula: see text]O2) increases with both 50 W-bicycle steps and suspended-weights ergometry (r = 0.97). During hyperbaric conditions, [Formula: see text]E was less increased versus normobaric conditions. Style group: the more efficient hip/thigh-oriented style shifted towards the knee/calf-oriented style. [Formula: see text]E and [Formula: see text]O2 were higher in beginners (< 100 dives) versus advanced divers (≥ 100 dives). Significant differences on the 5 kg-step: [Formula: see text]E: 31.5 ± 7.1 l/min vs. 23.7 ± 5.9 l/min and [Formula: see text]O2: 1.6 ± 0.3 l/min vs. 1.2 ± 0.3 l/min. A comparison is presented, in addition to illustrate the impact of differences in breathing characteristics and fin-swimming style. Conclusions Diving ergospirometry with suspended weights in a hyperbaric chamber allows for comprehensive studies. Little diving experience in terms of breathing characteristics and fin-swimming style significantly increases [Formula: see text]E thereby increasing the risk of running-out-of-air

Analysis of Single- and Double-Stranded DNA Damage in Osteoblastic Cells after Hyperbaric Oxygen Exposure

(1) Background: Hyperbaric oxygen (HBO) exposure induces oxidative stress that may lead to DNA damage, which has been observed in human peripheral blood lymphocytes or non-human cells. Here, we investigated the impact of hyperbaric conditions on two human osteoblastic cell lines: primary human osteoblasts, HOBs, and the osteogenic tumor cell line SAOS-2. (2) Methods: Cells were exposed to HBO in an experimental hyperbaric chamber (4 ATA, 100% oxygen, 37 °C, and 4 h) or sham-exposed (1 ATA, air, 37 °C, and 4 h). DNA damage was examined before, directly after, and 24 h after exposure with an alkaline comet assay and detection of γH2AX+53BP1 colocalizing double-strand break (DSB) foci and apoptosis. The gene expression of TGFß-1, HO-1, and NQO1, involved in antioxidative functions, was measured with qRT-PCR. (3) Results: The alkaline comet assay showed significantly elevated levels of DNA damage in both cell lines after 4 h of HBO, while the DSB foci were similar to sham. γH2AX analysis indicated a slight increase in apoptosis in both cell lines. The increased expression of HO-1 in HOB and SAOS-2 directly after exposure suggested the induction of an antioxidative response in these cells. Additionally, the expression of TGF-ß1 was negatively affected in HOB cells 4 h after exposure. (4) Conclusions: in summary, this study indicates that osteoblastic cells are sensitive to the DNA-damaging effects of hyperbaric hyperoxia, with the HBO-induced DNA damage consisting largely of single-strand DNA breaks that are rapidly repaired

Mechanical ventilation and resuscitation under water: Exploring one of the last undiscovered environments - A pilot study

INTRODUCTION: Airway management, mechanical ventilation and resuscitation can be performed almost everywhere - even in space - but not under water. The present study assessed the technical feasibility of resuscitation under water in a manikin model. METHODS: Tracheal intubation was assessed in a hyperbaric chamber filled with water at 20m of depth using the Pentax AWS S100 video laryngoscope, the Fastrach™ intubating laryngeal mask and the Clarus optical stylet with guidance by a laryngeal mask airway (LMA) and without guidance. A closed suction system was used to remove water from the airways. A test lung was ventilated to a maximum depth of 50m with a modified Oxylator(®) EMX resuscitator with its expiratory port connected either to a demand valve or a diving regulator. Automated chest compressions were performed to a maximum depth of 50m using the air-driven LUCAS™ 1. RESULTS: The mean cumulative time span for airway management until the activation of the ventilator was 36s for the Fastrach™, 57s for the Pentax AWS S100, 53s for the LMA-guided stylet and 43s for the stylet without LMA guidance. Complete suctioning of the water from the airways was not possible with the suction system used. The Oxylator(®) connected to the demand valve ventilated at 50m depth with a mean ventilation rate of 6.5min(-1) vs. 14.7min(-1) and minute volume of 4.5lmin(-1) vs. 7.6lmin(-1) compared to the surface. The rate of chest compression at 50m was 228min(-1) vs. 106min(-1) compared to surface. The depth of compressions decreased with increasing depth. CONCLUSION: Airway management under water appears to be feasible in this manikin model. The suction system requires further modification. Mechanical ventilation at depth is possible but modifications of the Oxylator(®) are required to stabilize ventilation rate and administered minute volumes. The LUCAS™ 1 cannot be recommended at major depth