MEDECINE DE PLONGEE
Physiologie de l'immersion
Aviat Space Environ Med.2014 May;85(5):509-17.
Thermal and metabolic responses of military divers during a 6-hour static dive in cold water.
BACKGROUND: Human thermal responses during prolonged whole-body immersion in cold water are of interest for the military, especially French SEALS. This study aims at describing the thermo-physiological responses. METHODS: There were 10 male military divers who were randomly assigned to a full immersion in neutral (34 degrees C), moderately cold (18 degrees C), and cold (10
degrees C) water wearing their operational protective devices (5.5 mm wetsuit with 3.0 mm thick underwear) for 6 h in a static position. Rectal temperature (T(re)) and 14 skin temperatures (T(sk)), blood analysis (stress biomarkers, metabolic substrates), and oxygen consumption (Vo2) were collected. RESULTS: At 34 degrees C, there were no significant modifications of the thermo-physiological responses over time. The most interesting result was that rates of rectal temperature decrease (0.15 +/- 0.02 degrees C x min(-1)) were the same between the two cold stress experimental conditions (at 18 degrees C and 10 degrees C). At the final experiment, rectal temperature was not significantly different between the two cold stress experimental conditions. Mean T(sk) decreased significantly during the first 3 h of immersion and then stabilized at a lower level at 10 degrees C (25.6 +/- 0.8 degrees C) than at 18 degrees C (29.3 +/- 0.9 degrees C). Other results demonstrate that the well-trained subjects developed effective physiological reactions. However, these reactions are consistently too low to counterbalance the heat losses induced by cold temperature conditions and long-duration immersion. CONCLUSION: This study shows that providing divers with thermal protection is efficient for a long-duration immersion from a medical point of view, but not from an operational one when skin extremities were taken into account.
Appl Physiol Nutr Metab.2014 Apr;39(4):425-31.
Effect of head-out water immersion on vascular function in healthy subjects.
Immersion in thermoneutral water increases cardiac output and peripheral blood flow and reduces systemic vascular resistance. This study examined the effects of head-out water immersion on vascular function. Twelve healthy middle-aged males were immersed during 60 min in the seated position, with water at the level of xiphoid. Local and central vascular tone regulating systems were studied during that time. Brachial artery diameter and blood flow were recorded using ultrasonography and Doppler. Endothelial function was assessed with flow-mediated dilation. Results were compared with the same investigations performed under reference conditions in ambient air. During water immersion, brachial artery diameter increased (3.7 ± 0.2 mm in ambient air vs. 4 ± 0.2 mm in water immersion; p < 0.05). Endothelium-mediated dilation was significantly lower in water immersion than in ambient air (10% vs. 15%; p = 0.01). Nevertheless, the difference disappeared when the percentage vasodilatation of the brachial artery was normalized to the shear stimulus. Smooth muscle-mediated dilation was similar in the 2 conditions. Spectral analysis of systolic blood pressure variability indicated a decrease in sympathetic vascular activity. Plasma levels of nitric oxide metabolites remained unchanged, whereas levels of natriuretic peptides were significantly elevated. An increase in brachial blood flow, a decrease in sympathetic activity, a warming of the skin, and an increase in natriuretic peptides might be involved in the increase in reference diameter observed during water immersion. Endothelial cell reactivity and smooth muscle function did not appear to be altered.
Accident de désaturation
Spinal Cord.2014 Mar;52(3):236-40.
Relation between cervical and thoracic spinal canal stenosis and the development of spinal cord decompression sickness in recreational scuba divers.
STUDY DESIGN: Retrospective case-control study. OBJECTIVES: The intent of this study was to investigate the relationships between vertebral degenerative changes resulting in spinal canal stenosis, spinal cord lesions and the development of spinal cord decompression sickness (DCS) in scuba divers. SETTING: Referral hyperbaric facility, Toulon, France. METHODS: We examined 33 injured divers less than 50 years old by cervical and thoracic MRI and compared them with 34 matched control divers. The number of intervertebral disk abnormalities and the degree of canal compression were analyzed on T2-weighted sagittal images using a validated grading system developed recently. The presence and the distribution of hyperintense cord lesions in relation with the accident and the recovery status at 6 months were also assessed. RESULTS: Canal spinal narrowing was more common in injured divers than in controls (79% vs. 50%, OR=3.7 [95% CI, 1.3-10.8], P=0.021). We found a significant linear association between the extent of canal stenosis, multisegmental findings and the development of spinal cord decompression sickness. MRI intramedullary lesions were significantly more frequent in divers with incomplete recovery (OR=16 [95% CI, 2.6-99], P=0.0014), but statistical analysis failed to demonstrate a significant relationship between canal compression, signal cord abnormalities and a negative clinical outcome. CONCLUSIONS: These results suggest that divers with cervical and thoracic spinal canal stenosis, mainly due to disk degeneration, are at increased risk for the occurrence of spinal cord decompression sickness.
Clin Kidney J.2014 Aug;7(4):380-2.
Acute kidney injury due to decompression illness.
Decompression illness is a rare but serious complication of diving caused by intravascular or extravascular gas bubble formation. We report the first case of acute kidney injury in a 27-year-old diver following three rapid ascents. He presented with transient neurological symptoms and abdominal pain followed by rapidly progressive acute kidney injury (creatinine peak 1210 µmol/L) due to arterialairemboli. He received supportive care and 100% oxygen followed by hyperbaric therapy and recovered fully. Arterialairemboli caused by rapid decompression can affect multiple organs including the kidneys. Early transfer to a hyperbaric unit is important as complications may present delayed.
Oedème Pulmonaire d'Immersion
Med Sci Sports Exerc.2014 Sep 12. [Epub ahead of print]
Immersion Pulmonary Edema and Comorbidities: Case Series and Updated Review.
PURPOSE: Immersion pulmonary edema occurs in swimmers (especially triathletes) and scuba divers. Its pathophysiology and risk factors are incompletely understood. This study was designed to establish the prevalence of pre-existing comorbidities in individuals who experience immersion pulmonary edema. METHODS: From 2008 to May 2010, individuals who had experienced immersion pulmonary edema were identified via recruitment for a physiological study. Past medical history and subject characteristics were compared with those available in the current body of literature. RESULTS: At Duke University Medical Center, Durham, NC, 36 subjects were identified (mean age 48.4 ± 9.1 years), of whom 72.2% had one or more significant medical conditions at the time of IPE incident (e.g., hypertension, cardiac dysrhythmias or structural abnormality or dysfunction, asthma, diabetes mellitus, overweight or obesity, obstructive sleepapnea, hypothyroidism). Forty-five articles were included, containing 292 cases of IPE, of which 24.0% had identifiable cardiopulmonary risk factors. Within the recreational population, cases with identifiable risk factors comprised 44.9%. Mean age was 47.8 ± 11.3 in recreational divers/swimmers and 23.3 ± 6.4 years in military divers/swimmers. CONCLUSION: Cardiopulmonary disease may be a common predisposing factor in immersion pulmonary edema in the recreational swimming/divingpopulation, while pulmonary hypertension due to extreme exertion may be more important in military cases. Individuals with past history of immersion pulmonary edema in our case series had a greater proportion of comorbidities compared to published cases. The role of underlying cardiopulmonary dysfunction may be underestimated, especially in older swimmers and divers. We conclude that an episode of immersion pulmonary edema should prompt evaluation of cardiac and pulmonary function.
Am J Gastroenterol.2000 Jan;95(1):285-8.
The striking effect of hyperbaric oxygenation therapy in the management of chronic idiopathic intestinal pseudo-obstruction.
Chronic idiopathic intestinal pseudo-obstruction is one of the disorders that is most refractory to medical and surgical treatment. Even when patients are given nutritional support, including total parenteral nutrition, obstructive symptoms seldom disappear. We report a case of chronic idiopathic intestinal pseudo-obstruction, due to myopathy, in which hyperbaric oxygenation therapy was strikingly effective. The presence of myopathy was histologically confirmed on the surgically resected jejunal specimen. Hyperbaric oxygenation resulted not only in relief of the patient's obstructive symptoms but also in a rapid decrease of abnormally accumulated intestinal gas. At last, he could resume oral intake without any critical adverse effects. These observations strongly suggest that hyperbaric oxygenation can be an effective therapy in the management of chronic idiopathic intestinal pseudo-obstruction.
Sécurité Santé au Travail
Med Lav.2015 Jan 9;106(1):17-22.
Occupational accidents in hyperbaric-chambers inside attendants in France.
INTRODUCTION: The purpose of the study was to assess the number of accidents among staff employed in the operation of hyperbaric chambers in France. MATERIALS AND METHODS: A retrospective study using a questionnaire was carried out on occupational accidents in France between 2005 and 2011. RESULTS: 12 (46%) centres participated in the study, representing 73 subjects. The mean age was 43.5 years (SD=9.73). They had worked in hyperbaric chambers for 9.8 years on average (SD=7.7). The average number of hyperbaric sessions was 198.3 per subject (SD=174.25), for a total of 8.072 hyperbaric sessions; 27% of the subjects reported that they had at least one accident during the study period. In all, 30 accidents were reported: 3 blood exposures, 4 accidents related to patient handling, 20 hyperbaric accidents; 3 other accidents. Of the hyperbaric accidents, 2 (10%) involved decompression sicknesses with cutaneous symptoms, 3 (15%) decompression illness (DCI), 14 (70%) ear traumatisms, 1 (5%) dental accident. The incidences were 372 per 100,000 sessions in hyperbaric chambers (SHC) for all accidents, 248 per 100,000 SHC for hyperbaric accidents and 173 per 100,000 SHC for ENT barotraumas. CONCLUSION: The accidents involving staff operating hyperbaric chambers were mainly ear traumatisms.