Temporary and permanent unfitness of occupational divers. Brest Cohort 2002-2019 from the French National Network for Occupational Disease Vigilance and Prevention (RNV3P).

BACKGROUND: In France, the monitoring of professional divers is regulated. Several learned societies (French Occupational Medicine Society, French Hyperbaric Medicine Society and French Maritime Medicine Society) have issued follow-up recommendations for professional divers, including medical follow-up. Medical decisions could be temporary unfitness for diving, temporary fitness with monitoring, a restriction of fitness, or permanent unfitness. The aim of study was to point out the causes of unfitness in our centre. MATERIALS AND METHODS: The divers' files were selected from the French National Network for Occupational Disease Vigilance and Prevention (RNV3P). Only files with a special medical decision were selected, between 2002 and 2019. RESULTS: Three hundred and ninety-six professional divers are followed-up in our centre and 1371 medical decisions were delivered. There were 29 (7.3%) divers with a special medical decision, during 42 (3.1%) medical visit. Twelve (3.0%) had a permanent unfitness. The leading cause of unfitness was pulmonary diseases: emphysema (3), chronic obstructive pulmonary disorder (2), asthma (2). Sixteen (4.0%) divers had temporary unfitness. The leading causes were cardiovascular (4 times) and neurological (6 times). Twelve (3.0%) divers had had at least one decompression sickness. CONCLUSIONS: Judgments of permanent unfitness for diving were rare (3.0% of divers), but were because of life-threatening disease. Medical follow-up of occupational divers was justified to decrease the risk of fatal event during occupational dives.

Venous gas embolism after an open-water air dive and identical repetitive dive.

Decompression tables indicate that a repetitive dive to the same depth as a first dive should be shortened to obtain the same probability of occurrence of decompression sickness (pDCS). Repetition protocols are based on small numbers, a reason for re-examination. Since venous gas embolism (VGE) and pDCS are related, one would expect a higher bubble grade (BG) of VGE after the repetitive dive without reducing bottom time. BGs were determined in 28 divers after a first and an identical repetitive air dive of 40 minutes to 20 meters of sea water. Doppler BG scores were transformed to log number of bubbles/cm2 (logB) to allow numerical analysis. With a previously published model (Model2), pDCS was calculated for the first dive and for both dives together. From pDCS, theoretical logBs were estimated with a pDCS-to-logB model constructed from literature data. However, pDCS the second dive was provided using conditional probability. This was achieved in Model2 and indirectly via tissue saturations. The combination of both models shows a significant increase of logB after the second dive, whereas the measurements showed an unexpected lower logB. These differences between measurements and model expectations are significant (p-values < 0.01). A reason for this discrepancy is uncertain. The most likely speculation would be that the divers, who were relatively old, did not perform physical activity for some days before the first dive. Our data suggest that, wisely, the first dive after a period of no exercise should be performed conservatively, particularly for older divers.

Recommendations for rescue of a submerged unresponsive compressed-gas diver.

The Diving Committee of the Undersea and Hyperbaric Medical Society has reviewed available evidence in relation to the medical aspects of rescuing a submerged unresponsive compressed-gas diver. The rescue process has been subdivided into three phases, and relevant questions have been addressed as follows. Phase 1, preparation for ascent: If the regulator is out of the mouth, should it be replaced? If the diver is in the tonic or clonic phase of a seizure, should the ascent be delayed until the clonic phase has subsided? Are there any special considerations for rescuing rebreather divers? Phase 2, retrieval to the surface: What is a "safe" ascent rate? If the rescuer has a decompression obligation, should they take the victim to the surface? If the regulator is in the mouth and the victim is breathing, does this change the ascent procedures? If the regulator is in the mouth, the victim is breathing, and the victim has a decompression obligation, does this change the ascent procedures? Is it necessary to hold the victim's head in a particular position? Is it necessary to press on the victim's chest to ensure exhalation? Are there any special considerations for rescuing rebreather divers? Phase 3, procedure at the surface: Is it possible to make an assessment of breathing in the water? Can effective rescue breaths be delivered in the water? What is the likelihood of persistent circulation after respiratory arrest? Does the recent advocacy for "compression-only resuscitation" suggest that rescue breaths should not be administered to a non-breathing diver? What rules should guide the relative priority of in-water rescue breaths over accessing surface support where definitive CPR can be started? A "best practice" decision tree for submerged diver rescue has been proposed.

The need for optimisation of post-dive ultrasound monitoring to properly evaluate the evolution of venous gas emboli.

Audio Doppler ultrasound and echocardiographic techniques are useful tools for investigating the formation of inert gas bubbles after hyperbaric exposure and can help to assess the risk of occurrence of decompression sickness. However, techniques, measurement period and regularity of measurements must be standardised for results to be comparable across research groups and to be of any benefit. There now appears to be a trend for fewer measurements to be made than recommended, which means that the onset, peak and cessation of bubbling may be overlooked and misreported. This review summarises comprehensive Doppler data collected over 15 years across many dive profiles and then assesses the effectiveness of measurements made between 30 and 60 minutes (min) post-dive (commonly measured time points made in recent studies) in characterising the evolution and peak of venous gas emboli (VGE). VGE evolution in this dive series varied enormously both intra- and inter-individually and across dive profiles. Median, rather than mean values are best reported when describing data which have a non-linear relation to the underlying number of bubbles, as are median peak grades, rather than maximum, which may reflect only one individual's data. With regard to monitoring, it is apparent that the evolution of VGE cannot be described across multiple dive profiles using measurements made at only 30 to 60 min, or even 90 min post-dive. Earlier and more prolonged measurement is recommended, while the frequency of measurements should also be increased; in doing so, the accuracy and value of studies dependent on bubble evolution will be improved.

Determining standards for professional divers diving in benzene polluted waters.

The main objective of this study is to calculate the hours of diving in benzene-polluted waters acceptable for professional divers. We considered recommended absorption limit as that from pulmonary workplace absorption during an 8-h workday at recommended exposure limits set by the National Institute of Occupational Safety and Health, and developed a formula to determine recommended limits for diving time based on actual water and sediment concentrations and exposure conditions. The recommended absorption limit is 1.6 mg of benzene per workday. This is equivalent to total body dermal absorption over a 1-h dive at water concentration of 7.6 mg/L, or absorption from drinking 0.1 L of water with a concentration of 16.5 mg/L, or dermal absorption with 50% of the body covered in sediment with a concentration of 18,851 mg/kg. A formula that calculates allowable diving time considering benzene water and sediment concentrations, and gastrointestinal and dermal exposures is presented. Water concentrations and not exposure to sediment limit recommended diving time, and unlimited diving in areas with sediment and water concentrations thought to pose a serious human health hazard would not surpass the recommended amount of benzene absorbed in the workplace. We conclude that allowable diving time in polluted waters can be calculated resulting in absorption equivalent to recommended limits for pulmonary absorption in the workplace. Our results suggest that agencies determining significant health risk levels of chemical concentrations in sediment and water should consider our findings.

[Fitness to dive in the otorhinolaryngological field]. / Tauchtauglichkeit im HNO-Bereich.

In line with the rising number of recreational divers, the otorhinolaryngologist has to deal with growing numbers of diving-associated disorders of the ear, nose and throat (ENT). Nevertheless, the majority of divers present to their ENT doctor for assessment of their fitness to dive. On the basis of long-term follow-up examinations and increasing experience in diving medicine, even divers with a history of ENT problems can be considered fit to dive. Therefore, diving is possible after tympanoplasty, surgery to improve hearing including stapesplasty, after implantation of middle ear amplifiers or cochlear implants, after sinus or scull base surgery and even after canal wall down mastoidectomy, provided that certain requirements are fulfilled. Assessing fitness to dive after inner ear barotrauma as well as after inner ear decompression illness requires meticulous consideration of residual damage and possible underlying conditions like vascular right-to-left shunts. This article is based on the new recommendations of the German Undersea and Hyperbaric Medical Society for the assessment of fitness to dive in the otorhinolaryngological field.

Otolaryngological requirements for recreational self-contained underwater breathing apparatus (SCUBA) diving.

Recreational self-contained underwater breathing apparatus (SCUBA) diving continues to grow in popularity. Medical requirements to be 'fit to dive' vary throughout the world, from self-certification to a full medical examination prior to training. This review discusses the relative merits of the most commonly used guidelines for recreational SCUBA diving, with reference to common diving-related otorhinolaryngological conditions. Areas of controversy, such as fitness to dive after rhinological and otological surgery, are discussed. The authors suggest that a unified approach from the various recreational SCUBA diving organizations involved would aid in clarification for divers and physicians alike. The difficulties in achieving such a unified approach, however, should not be underestimated.

A deep stop during decompression from 82 fsw (25 m) significantly reduces bubbles and fast tissue gas tensions.

In spite of many modifications to decompression algorithms, the incidence of decompression sickness (DCS) in scuba divers has changed very little. The success of stage, compared to linear ascents, is well described yet theoretical changes in decompression ratios have diminished the importance of fast tissue gas tensions as critical for bubble generation. The most serious signs and symptoms of DCS involve the spinal cord, with a tissue half time of only 12.5 minutes. It is proposed that present decompression schedules do not permit sufficient gas elimination from such fast tissues, resulting in bubble formation. Further, it is hypothesized that introduction of a deep stop will significantly reduce fast tissue bubble formation and neurological DCS risk. A total of 181 dives were made to 82 fsw (25 m) by 22 volunteers. Two dives of 25 min and 20 min were made, with a 3 hr 30 min surface interval and according to 8 different ascent protocols. Ascent rates of 10, 33 or 60 fsw/min (3, 10, 18 m/min) were combined with no stops or a shallow stop at 20 fsw (6 m) or a deep stop at 50 fsw (15 m) and a shallow at 20 fsw (6 m). The highest bubbles scores (8.78/9.97), using the Spencer Scale (SS) and Extended Spencer Scale (ESS) respectively, were with the slowest ascent rate. This also showed the highest 5 min and 10 min tissue loads of 48% and 75%. The lowest bubble scores (1.79/2.50) were with an ascent rate of 33 fsw (10 m/min) and stops for 5 min at 50 fsw (15 m) and 20 fsw (6 m). This also showed the lowest 5 and 10 min tissue loads at 25% and 52% respectively. Thus, introduction of a deep stop significantly reduced Doppler detected bubbles together with tissue gas tensions in the 5 and 10 min tissues, which has implications for reducing the incidence of neurological DCS in divers.

[Health aspects of diving in ENT medicine. Part II: Diving fitness]. / Tauchmedizinische Aspekte in der HNO-Heilkunde. 2.Teil: Tauchtauglichkeit.

Diving has become increasingly popular. With the growing number of patients who want to dive, there is an increasing number of divers who require their regular medical examination. As ENT problems are the most common disorders in divers, otorhinolaryngologists regularly have to assess the diver's fitness. It should be noted that an ENT examination does not certify complete fitness to dive! Diving can be resumed 3 months after middle ear surgery, especially after tympanoplastic type I, II and III with insertion of a PORP, when there is regular middle ear ventilation without atrophic scars of the tympanic membrane. Even after stapes surgery, diving can be resumed when there are no signs of vestibular irritation during a provocation test. By 3 months after sinus surgery, the diver should perform a test dive under supervision before fitness to dive can be certified. After inner ear barotrauma, the diver remains fit to dive depending on his hearing ability in the involved ear. After inner ear decompression illness, one should look for a vascular right-to-left shunt before diving can be resumed. These and many more aspects are discussed in this article on how to determine whether a diver with ENT problems is fit to dive.

Thermal insulation properties of argon used as a dry suit inflation gas.

Uncontrolled observations from the "technical" diving community claim superior thermal comfort when replacing air with argon as dry suit inflation gas during diving. The objective of the present experiment was to evaluate the effectiveness of argon compared to air during cold water diving. Body weight, urinary output, and rectal and skin temperatures were measured in six naval divers during two dives to approximately 10 m for 60 min. Level of thermal comfort was reported. Dry suit gas was either argon or air, divers and scientists were blinded for gas identity. Urinary output was approximately 200 ml less (P < 0.05) during the air than the argon dives. Rectal and all skin temperatures decreased significantly in both groups during the dive but no difference was measured between argon and air dives. Thermal comfort was not different between the groups. Replacing air with argon neither improves subjective impression of thermal comfort nor attenuates core or skin cooling during cold water diving to 10 meters of sea water for 60 min.

Evaluación morfológica y recomendación de normas para el buzo cubano / Morphological evaluation and recommendation of standards for the Cuban diver

Desde el año 1993 se realiza en el ISMM "Dr. Luis Díaz Soto" el estudio antropométrico como parte del examen médico anual de control de salud al personal de buceo, aunque no existe aún en el país una norma cubana que establezca los parámetros morfológicos para evaluar a este personal. Con los exámenes realizados en el Centro de Medicina de Aviación y Subacuática en los años 1993 y 1994 a estos especialistas, se acometió el trabajo que culminó con la elaboración de la presente recomendación de normas. Se tuvieron en cuenta 13 mediciones antropométricas con las que se obtuvieron 7 variables de composición corporal y 3 de somatotipo. Todas las variables se procesaron en el programa MICROSTAD y mediante un método estadístico universalmente aceptado se llegó al establecimiento de dichas normas para el buzo cubano. Se concluyó que el buzo cubano es un hombre adulto, joven, sano, mesoectomórfico, de 28,7 años de edad, que mide 172,9 cm, pesa 68,5 kg y tiene un porcentaje de grasa de 13,74