How do we fight COVID-19? Military medical actions in the war against the COVID-19 pandemic in France.

'We are at war', French President Emmanuel Macron said in an address to the nation on 16 March 2020. As part of this national effort, the French Military Medical Service (FMMS) is committed to the fight against COVID-19. This original report aimed to describe and detail actions that the FMMS has carried out in the nationwide fight against the COVID-19 pandemic in France, as well as overseas. Experts in the field reported major actions conducted by the FMMS during the COVID-19 pandemic in France. In just few weeks, the FMMS developed ad hoc medical capabilities to support national health authorities. It additionally developed adaptive, collective en route care via aeromedical and naval units and deployed a military intensive care field hospital. A COVID-19 crisis cell coordinated the French Armed Forces health management. The French Military Centre for Epidemiology and Public Health provided all information needed to guide the decision-making process. Medical centres of the French Armed Forces organised the primary care for military patients, with the widespread use of telemedicine. The Paris Fire Brigade and the Marseille Navy Fire Battalion emergency departments ensured prehospital management of patients with COVID-19. The eight French military training hospitals cooperated with civilian regional health agencies. The French military medical supply chain supported all military medical treatment facilities in France as well as overseas, coping with a growing shortage of medical equipment. The French Armed Forces Biomedical Research Institute performed diagnostics, engaged in multiple research projects, updated the review of the scientific literature on COVID-19 daily and provided expert recommendations on biosafety. Finally, even students of the French military medical academy volunteered to participate in the fight against the COVID-19 pandemic. In conclusion, in an unprecedented medical crisis, the FMMS engaged multiple innovative and adaptive actions, which are still ongoing, in the fight against COVID-19. The collaboration between military and civilian healthcare systems reinforced the shared objective to achieve the goal of 'saving the greatest number'.

Exhaled nitric oxide concentration and decompression-induced bubble formation: An index of decompression severity in humans?

INTRODUCTION: Previous studies have highlighted a decreased exhaled nitric oxide concentration (FE NO) in divers after hyperbaric exposure in a dry chamber or following a wet dive. The underlying mechanisms of this decrease remain however unknown. The aim of this study was to quantify the separate effects of submersion, hyperbaric hyperoxia exposure and decompression-induced bubble formation on FE NO after a wet dive. METHODS: Healthy experienced divers (n=31) were assigned to either (i) a group making a scuba-air dive (Air dive), (ii) a group with a shallow oxygen dive protocol (Oxygen dive) or (iii) a group making a deep dive breathing a trimix gas mixture (deep-dive). Bubble signals were graded with the KISS score. Before and after each dive FE NO values were measured using a hand-held electrochemical analyzer. RESULTS: There was no change in post-dive values of FE NO values (expressed in ppb=parts per billion) in the Air dive group (15.1 ± 3.6 ppb vs. 14.3 ± 4.7 ppb, n=9, p=0.32). There was a significant decrease in post-dive values of FE NO in the Oxygen dive group (15.6 ± 6 ppb vs. 11.7 ± 4.7 ppb, n=9, p=0.009). There was an even more pronounced decrease in the deep dive group (16.4 ± 6.6 ppb vs. 9.4 ± 3.5 ppb, n=13, p<0.001) and a significant correlation between KISS bubble score >0 (n=13) and percentage decrease in post-dive FE NO values (r=-0.53, p=0.03). DISCUSSION: Submersion and hyperbaric hyperoxia exposure cannot account entirely for these results suggesting the possibility that, in combination, one effect magnifies the other. A main finding of the present study is a significant relationship between reduction in exhaled NO concentration and dive-induced bubble formation. We postulate that exhaled NO concentration could be a useful index of decompression severity in healthy human divers.

Effect of oxygen-breathing during a decompression-stop on bubble-induced platelet activation after an open-sea air dive: oxygen-stop decompression.

PURPOSE: We highlighted a relationship between decompression-induced bubble formation and platelet micro-particle (PMP) release after a scuba air-dive. It is known that decompression protocol using oxygen-stop accelerates the washout of nitrogen loaded in tissues. The aim was to study the effect of oxygen deco-stop on bubble formation and cell-derived MP release. METHODS: Healthy experienced divers performed two scuba-air dives to 30 msw for 30 min, one with an air deco-stop and a second with 100% oxygen deco-stop at 3 msw for 9 min. Bubble grades were monitored with ultrasound and converted to the Kisman integrated severity score (KISS). Blood samples for cell-derived micro-particle analysis (AnnexinV for PMP and CD31 for endothelial MP) were taken 1 h before and after each dive. RESULTS: Mean KISS bubble score was significantly lower after the dive with oxygen-decompression stop, compared to the dive with air-decompression stop (4.3 ± 7.3 vs. 32.7 ± 19.9, p < 0.001). After the dive with an air-breathing decompression stop, we observed an increase of the post-dive mean values of PMP (753 ± 245 vs. 381 ± 191 ng/µl, p = 0.003) but no significant change in the oxygen-stop decompression dive (329 ± 215 vs. 381 +/191 ng/µl, p = 0.2). For the post-dive mean values of endothelial MP, there was no significant difference between both the dives. CONCLUSIONS: The Oxygen breathing during decompression has a beneficial effect on bubble formation accelerating the washout of nitrogen loaded in tissues. Secondary oxygen-decompression stop could reduce bubble-induced platelet activation and the pro-coagulant activity of PMP release preventing the thrombotic event in the pathogenesis of decompression sickness.

Paradoxical gas embolism after SCUBA diving: hemodynamic changes studied by echocardiography.

Hemodynamic changes induced by self-contained underwater breathing apparatus diving were investigated using Doppler echocardiography. We detected circulating bubbles in both right and left cavities of the heart and in the cerebral circulation in two divers with a large patent foramen ovale. A reduction in the left ventricular preload was suggested by echocardiographic measurements. The decreased cardiac preload was paralleled to a lower stroke volume and cardiac output. These findings were also observed in divers with no evidence of circulating bubbles. In these subjects, pulmonary vascular resistances remained unchanged while an increase was observed in the two divers with arterial bubbles. This increase could promote right-to-left shunting.

Preventive effect of pre-dive hydration on bubble formation in divers.

OBJECTIVE: To investigate whether prehydration 90 min before a dive could decrease bubble formation, and to evaluate the consequent adjustments in plasma volume (PV), water balance and plasma surface tension (ST). METHODS: Eight military divers participated in a crossover trial of pre-dive hydration using saline-glucose beverage (protocol 1) and a control dive with no prehydration (protocol 2). Drink volume was 1300 ml (osmolality 324 mOsm/l) and drinking time was 50-60 min. The diving protocol consisted of an open sea field air dive at 30 msw depth for 30 min followed by a 9 min stop at 3 msw. Haemodynamic parameters, body weight measurements, urine volume and blood samples were taken before/after fluid intake and after the dive. Decompression bubbles were examined by a precordial pulsed Doppler. RESULTS: Bubble activity was significantly lower for protocol 1 than for protocol 2. PV increased after fluid ingestion by 3.5% and returned toward baseline after diving for protocol 1, whereas it decreased by 2.2% after diving for protocol 2. Differences in post-dive PV between the two conditions were highly significant. Body weight loss before/after diving and post-dive urine volume after diving were significant in both protocols, but the relative decline in weight remained lower for protocol 1 than for protocol 2, with reduction of negative water balance due to higher fluid retention. There were no differences in ST after fluid intake and after diving for the two protocols. CONCLUSION: Pre-dive oral hydration decreases circulatory bubbles, thus offering a relatively easy means of reducing decompression sickness risk. The prehydration condition allowed attenuation of dehydration and prevention of hypovolaemia induced by the diving session. Hydration and diving did not change plasma surface tension in this study.

Influence of repetitive open sea dives and physical exercises on right-to-left shunting in healthy divers.

OBJECTIVE: Paradoxical gas embolism through right-to-left (R/L) shunts is considered as a potential cause of certain types of decompression sickness. AIM: To assess whether 4 months of repetitive diving and strenuous exercises would lead to an increased prevalence of R/L shunting in a group of military divers. METHODS: Using a standardised contrast-enhanced transcranial Doppler technique, 17 divers were re-examined for the presence of a R/L shunt 4 months after their initial examinations. R/L shunts were classified as type I if observed only after a straining manoeuvre, and type II if present at rest. RESULTS: Initial prevalence of R/L shunt was 41%: six type I shunts and one type II. At the second examination, prevalence was 47%, with the appearance of one type I shunt that was not previously present. We found no significant increase in the prevalence and size of R/L shunts. CONCLUSION: It is speculated that diving-related phenomena, such as variations in right atrial pressures during the end stages of or events immediately after a dive could generate an R/L shunt. However, extreme conditions of repetitive diving and strenuous exercises do not cause permanent modification in R/L permeability over a period of 4 months.

[Decompression sickness accident management in remote areas. Use of immediate in-water recompression therapy. Review and elaboration of a new protocol targeted for a mission at Clipperton atoll]. / Gestion d'un accident de plongée en situation d'isolement. Intérêt de la recompression thérapeutique par immersion. Revue et proposition d'un nouveau protocole à l'occasion d'une mission sur l'atoll de Clipperton.

In-Water Recompression (IWR) is defined as a treatment of decompression sickness by immediate underwater recompression after the onset of symptoms in remote areas where hyperbaric chambers are not available. At least three methods of IWR have been published. They used pure oxygen breathing for prolonged periods of time at a depth of 9 m. IWR effectiveness in comparison with standard recompression techniques has not been assessed. IWR should be used in remote localities as an immediate measure to stop the evolution of decompression illness before evacuating the victim for subsequent treatment to the nearest hyperbaric facility. Resulting from environmental conditions, the risks of drowning and hypothermia are the most often quoted, pure oxygen breathing at 9 m can also expose to acute oxygen toxicity. The objectives of this work are: first, to examine existing published methods of IWR; second, to propose a new method of IWR. All published methods of IWR involve victim returning underwater for a long period of time. But dehydration due to a long period of immersion can worsen symptoms of decompression illness and acute oxygen toxicity is also related to the duration of the exposition. In response to these considerations we developed a shorter method of conducting IWR specifically targeted for a diving mission at Clipperton atoll in the Northern Pacific Ocean.