Vascular Function Recovery Following Saturation Diving.

Background and Objectives: Saturation diving is a technique used in commercial diving. Decompression sickness (DCS) was the main concern of saturation safety, but procedures have evolved over the last 50 years and DCS has become a rare event. New needs have evolved to evaluate the diving and decompression stress to improve the flexibility of the operations (minimum interval between dives, optimal oxygen levels, etc.). We monitored this stress in saturation divers during actual operations. Materials and Methods: The monitoring included the detection of vascular gas emboli (VGE) and the changes in the vascular function measured by flow mediated dilatation (FMD) after final decompression to surface. Monitoring was performed onboard a diving support vessel operating in the North Sea at typical storage depths of 120 and 136 msw. A total of 49 divers signed an informed consent form and participated to the study. Data were collected on divers at surface, before the saturation and during the 9 h following the end of the final decompression. Results: VGE were detected in three divers at very low levels (insignificant), confirming the improvements achieved on saturation decompression procedures. As expected, the FMD showed an impairment of vascular function immediately at the end of the saturation in all divers but the divers fully recovered from these vascular changes in the next 9 following hours, regardless of the initial decompression starting depth. Conclusion: These changes suggest an oxidative/inflammatory dimension to the diving/decompression stress during saturation that will require further monitoring investigations even if the vascular impairement is found to recover fast.

Review of saturation decompression procedures used in commercial diving.

Introduction: This is a review of commercial heliox saturation decompression procedures. The scope does not include compression, storage depth or bell excursion dive procedures. The objectives are to: identify the sources of the procedures; trace their evolution; describe the current practice; and detect relevant trends. Methods: Eleven international commercial diving companies provided their diving manuals for review under a confidentiality agreement. Results: Modern commercial diving saturation procedures are derived from a small number of original procedures (United States Navy, Comex, and NORSOK). In the absence of relevant scientific studies since the late 80's, the companies have empirically adapted these procedures according to their needs and experience. Such adaptation has caused differences in decompression rates shallower than 60 msw, decompression rest stops and the decision to decompress linearly or stepwise. Nevertheless, the decompression procedures present a remarkable homogeneity in chamber PO2 and daily decompression rates when deeper than 60 msw. The companies have also developed common rules of good practice; no final decompression should start with an initial ascending excursion; a minimum hold is required before starting a final decompression after an excursion dive. Recommendation is made for the divers to exercise during decompression. Conclusions: We observed a trend towards harmonisation within the companies that enforce international procedures, and, between companies through cooperation inside the committees of the industry associations.

Evaluation of North Sea saturation procedures through divers monitoring.

BACKGROUND: Saturation diving is a standard method of intervention for commercial diving during offshore operations. Current saturation procedures achieve a high level of safety with regards to decompression sickness but still put the divers under multiple stressors: 1) Environmental stress (long confinement, heat/cold, dense gases, high oxygen levels), 2) Work stress (muscular fatigue, psychological pressure, breathing equipment, etc.), 3) venous gas emboli associated with decompression, 4) Inflammation related to oxidative stress and microparticles. We present the results of a saturation divers monitoring campaign performed in the North Sea Danish sector, on the Tyra field, during 2022. The study was supported by TotalEnergies, the field operator, and performed by Boskalis Subsea Services, the diving contractor, onboard the diving support vessel Boka Atlantis. The objective was twofold: document the level of diving stress during saturation operations in the Danish sector, and compare the performances of two saturation procedures, the Boskalis and the NORSOK procedures. MATERIALS AND METHODS: Fourteen divers volunteered for the study. The monitoring package include weight and temperature measurements, psychomotor tests (objective evaluation) and questionnaires (subjective evaluation), Doppler bubble detection and bioimpedance. The results were presented in a radar diagram that provides a general view of the situation. RESULTS: The data were analysed along 3 dimensions: work and environmental, desaturation bubbles, oxidative stress and inflammation. The results showed little or no variations from the reference values. No bubbles were detected after excursion dives and the final decompression, except for two divers with a grade 1 after arriving at surface. No statistical difference could be found between the Boskalis and the NORSOK saturation procedures. CONCLUSIONS: At a depth of 40-50 msw corresponding to the Danish sector, the two saturation procedures monitored induce no or little stress to the divers. The divers know how to manage their diet, equilibrate their hydration and pace their effort. Data available on divers' post saturation period show a recovery over the 24-48 hours following the end of the decompression. Further research should focus on diving deeper than 100 msw where a greater stress can be anticipated.

A review of accelerated decompression from heliox saturation in commercial diving emergencies.

INTRODUCTION: Saturation diving is a specialised method of intervention in offshore commercial diving. Emergencies may require the crew to be evacuated from the diving support vessel. Because saturation divers generally need several days to reach surface, the emergency evacuation of divers is based on dedicated hyperbaric rescue systems. There are still potential situations for which these systems cannot be used or deployed, and where an emergency decompression provides an alternative solution. METHODS: Our objective was to describe historical cases and assess the benefit of emergency decompressions, with the collection of data from the authors' direct experience and networks, providing witness or first-hand information. RESULTS: We documented three cases of emergency decompression following bell evacuations, and six cases of accelerated decompression performed in the chamber or hyperbaric rescue chamber. Review of these cases showed: 1) the complicated nature of such emergencies that make decisions difficult; 2) the variety of solutions implemented; and 3) the surprisingly safe and successful outcomes of several operations. Analysis of the accelerated decompression occurrences allowed derivation of the options used; upward initial excursion, increased chamber partial pressure of oxygen associated to increased ascent rates, and inert gas switching. We identified four published procedures for accelerated decompression. CONCLUSIONS: Despite modern hyperbaric rescue systems, accelerated decompression remains an essential tool in case of emergency. The diving industry needs clear guidance on what can be achieved, depending on the saturation depth and the level of emergency.

Hydration status during commercial saturation diving measured by bioimpedance and urine specific gravity.

Excessive fluid loss triggered by hyperbaric pressure, water immersion and hot water suits causes saturation divers to be at risk of dehydration. Dehydration is associated with reductions in mental and physical performance, resulting in less effective work and an increased risk of work-related accidents. In this study we examined the hydration status of 11 male divers over 19 days of a commercial saturation diving campaign to a working depth of 74 m, using two non-invasive methods: Bioelectrical impedance analysis (BIA) and urine specific gravity (USG). Measurements were made daily before and after bell runs, and the BIA data was used to calculated total body water (TBW). We found that BIA and USG were weakly negatively correlated, probably reflecting differences in what they measure. TBW was significantly increased after bell runs for all divers, but more so for bellmen than for in-water divers. There were no progressing changes in TBW over the 19-day study period, indicating that the divers' routines were sufficient for maintaining their hydration levels on short and long term.

Static Metabolic Bubbles as Precursors of Vascular Gas Emboli During Divers' Decompression: A Hypothesis Explaining Bubbling Variability.

INTRODUCTION: The risk for decompression sickness (DCS) after hyperbaric exposures (such as SCUBA diving) has been linked to the presence and quantity of vascular gas emboli (VGE) after surfacing from the dive. These VGE can be semi-quantified by ultrasound Doppler and quantified via precordial echocardiography. However, for an identical dive, VGE monitoring of divers shows variations related to individual susceptibility, and, for a same diver, dive-to-dive variations which may be influenced by pre-dive pre-conditioning. These variations are not explained by currently used algorithms. In this paper, we present a new hypothesis: individual metabolic processes, through the oxygen window (OW) or Inherent Unsaturation of tissues, modulate the presence and volume of static metabolic bubbles (SMB) that in turn act as precursors of circulating VGE after a dive. METHODS: We derive a coherent system of assumptions to describe static gas bubbles, located on the vessel endothelium at hydrophobic sites, that would be activated during decompression and become the source of VGE. We first refer to the OW and show that it creates a local tissue unsaturation that can generate and stabilize static gas phases in the diver at the surface. We then use Non-extensive thermodynamics to derive an equilibrium equation that avoids any geometrical description. The final equation links the SMB volume directly to the metabolism. RESULTS AND DISCUSSION: Our model introduces a stable population of small gas pockets of an intermediate size between the nanobubbles nucleating on the active sites and the VGE detected in the venous blood. The resulting equation, when checked against our own previously published data and the relevant scientific literature, supports both individual variation and the induced differences observed in pre-conditioning experiments. It also explains the variability in VGE counts based on age, fitness, type and frequency of physical activities. Finally, it fits into the general scheme of the arterial bubble assumption for the description of the DCS risk. CONCLUSION: Metabolism characterization of the pre-dive SMB population opens new possibilities for decompression algorithms by considering the diver's individual susceptibility and recent history (life style, exercise) to predict the level of VGE during and after decompression.

Commercial Divers' Subjective Evaluation of Saturation.

Commercial saturation diving involves divers living and working in an enclosed atmosphere with elevated partial pressure of oxygen (ppO2) for weeks. The divers must acclimatize to these conditions during compression, and for up to 28 days until decompression is completed. During decompression, the ppO2 and ambient pressure are gradually decreased; then the divers must acclimatize again to breathing normal air in atmospheric pressure when they arrive at surface. We investigated 51 saturation divers' subjective evaluation of the saturation and post-decompression phase via questionnaires and individual interviews. The questions were about decompression headaches and fatigue; and time before recovering to a pre-saturation state. Twenty-two (44%) of the divers who responded declared having headaches; near surface (44%) or after surfacing (56%). 71% reported post-saturation fatigue after their last saturation, 82% of them described it as typical and systematic after each saturation. Recovery was reported to normally take from 1 to 10 days. The fatigue and headaches observed are compatible with divers' acclimatization to the changes in ppO2 levels during saturation and decompression. They appear to be reversible post- decompression.

[Value of MRI in hepatic plexiform neurofibromatosis. Case report]. / Apport de l'imagerie par résonance magnétique dans la neurofibromatose plexiforme hépatique. A propos d'un cas.

Neurofibromatosis of the liver is a rare localization of type 1 neurofibromatosis. In terms of nature and local extension of the tumor, MR imaging provided accurate information compared to ultrasonography and computed tomography scan. Furthermore, MR imaging should be the first line noninvasive exploration for follow-up or biopsy guidance if progression to sarcomatosis is suspected.

Percutaneous vertebroplasty: indications, technique, and results.

The authors describe a dedicated therapeutic vertebroplasty technique that uses newly designed instruments, acrylic cement, and dual guidance with ultrasonography and computed tomography for pain control in patients with bone failure, and report their experience. Between 1990 and 2002, they performed 868 percutaneous cementoplasty procedures in patients with severe osteoporosis, vertebral tumors, and symptomatic hemangiomas. In patients with osteoporosis, satisfactory results were obtained in 78% of cases; in patients with vertebral tumors, satisfactory results were obtained in 83% of cases; and in patients with hemangiomas, satisfactory results were obtained in 73% of cases. In the global series of 868 cementoplasties, an epidural leak was observed in 15 cases, which caused neuralgia in only three patients without spinal cord compression. In two patients, an asymptomatic pulmonary embolism was detected. The needle of the new vertebroplasty set is designed with side wings for easier rotation and removal. The screw syringe increases the precision of injection. The risk of leak is substantially reduced. The system is safe, reduces the cement manipulation time, and allows excellent control of the injection. The authors performed 130 vertebroplasties with this system without major complications.