Adaptative mechanism of the equilibrative nucleoside transporter 1 (ENT-1) and blood adenosine levels in elite freedivers.

PURPOSE: Long static or intense dynamic apnoea-like high-altitude exposure is inducing hypoxia. Adenosine is known to participate to the adaptive response to hypoxia leading to the control of heart rate, blood pressure and vasodilation. Extracellular adenosine level is controlled through the equilibrative nucleoside transporter 1 (ENT-1) and the enzyme adenosine deaminase (ADA). The aim of this study was to determine the control of adenosine blood level (ABL) via ENT-1 and ADA during apnoea-induced hypoxia in elite freedivers was similar to high-altitude adaptation. METHODS: Ten freediver champions and ten controls were studied. Biological (e.g. ENT-1, ADA, ABL, PaO2, PaCO2 and pH) and cardiovascular (e.g. heart rate, arterial pressure) parameters were measured at rest and after a submaximal dry static apnoea. RESULTS: In freedivers, ABL was higher than in control participants in basal condition and increased more in response to apnoea. Also, freedivers showed an ADA increased in response to apnoea. Finally, ENT-1 level and function were reduced for the free divers. CONCLUSION: Our results suggest in freedivers the presence of an adaptive mechanism similar to the one observed in human exposed to chronic hypoxia induced by high-altitude environment.

[Serious pulmonary barotrauma in a child after first-time scuba dive]. / Accident barotraumatique grave chez un enfant lors d'un baptême de plongée.

Scuba diving is increasingly popular for children. However, this activity, including in shallow water, can be responsible for severe accidents. We report the case of a 13-year-old boy who dove for the first time in the Mediterranean Sea and suffered pulmonary barotraumas, complicated by arterial gas embolism with pneumomediastinum, cerebral, and coronary injuries. Any symptoms occurring after a dive, even in shallow water, must be considered a diving accident. Emergency medical personnel should contact a hyperbaric center for advice. In case of coronary or cerebral gaseous embolism, specific management requiring therapeutic recompression is urgently required.

[Middle ear barotraumas due to rhinopharyngeal scar tissue: tubomanometry diagnostic and therapeutic contribution]. / Barotraumatismes de l'oreille moyenne par brides rhinopharyngées: intérêt diagnostique et thérapeutique de la tubomanométrie.

OBJECTIVE: Evaluation of tubomanometry contribution to diagnosis middle ear barotraumas in relation with rhinopharyngeal scar tissue, and contribution to check postoperative effectiveness of scar tissue surgical resection. METHODS: Clinical cases study of two stewardesses who have lost their flight fitness consecutively to barotraumatic otitis during landing, engendered by rhinopharyngeal scar tissue. RESULTS: Pre-operative tubomanometric parameters were abnormal in both cases: decrease of intratympanic pressure in one case, variability of tube opening latency index and lengthening of intratympanic pressure rising time in the other case. Surgical section during endonasal endoscopy results in initially abnormal tubomanometric parameters normalization, allowing resumption of flight fitness without any barotrauma. CONCLUSION: Some abnormal tubomanometric parameters help to establish causality link between middle ear barotrauma and rhinopharyngeal scar tissue for which surgical section is thus indicated. Post-operative tubomanometric parameters normalization prove surgical effectiveness. Then, flight fitness could then be restored.

Fin swimming improves respiratory gas exchange.

Data in the literature suggest that compared to dry-land exercise fin swimming might delay the activation of the anaerobic metabolism. To verify this hypothesis, we explored indirect indices such as the oxygen pulse (VO(2)/HR), carbon dioxide production (VCO(2)), and ventilatory threshold, comparing fin swimming exercise to dry-land cycling. Thirteen participants, experienced or inexperienced in fin swimming, completed an incremental fin swimming exercise and a maximal exercise on a cycloergometer with breath-by-breath measurements of heart rate (HR), ventilation (VE), tidal volume (VT), VO(2), VCO(2), and VO(2)/HR and determination of the ventilatory threshold and maximal oxygen uptake (VO(2)max). Compared to dry-land cycling exercise, fin swimming resulted in elevated or absent ventilatory threshold. Although VO(2)max did not differ in either condition, in fin swimming the maximal HR value was lower (-18%, p=0.0072), maximal VO(2)/HR higher (+20%, p=0.0325), and maximal VCO(2) lower (-17%, p=0.0071). We also measured significant reduction of VE, VT, and HR variations for the same VO(2) increase. This study suggests that the anaerobic muscle metabolism might be delayed in fin swimming. An attenuated chemoreflex drive to the heart and respiratory centres exerted by muscle metabolites might explain the depressed cardiopulmonary response to fin swimming.