Cardiac alterations induced by a fish-catching diving competition.

Cardiac changes induced by repeated breath-hold diving were investigated after a fish-catching diving competition. Eleven healthy subjects carried out repeated breath-hold dives at a mean maximal depth of 20 ± 2.7 msw (66 ± 9 fsw) during 5 h. One hour after the competition, the body mass loss was -1.7 ± 0.5 kg. Most of the breath-hold divers suffered from cold and although the core temperature remained normal, a decrease in cutaneous temperature was recorded in the extremities. Systolic blood pressure was reduced in both upper and lower limbs. Heart rate was unchanged, but left ventricular (LV) stroke volume was reduced leading to a decrease in cardiac output (-20%). Left atrial and LV diameters were significantly decreased. LV filling was assessed on a trans-mitral profile. An increase in the contribution of the atrial contraction to LV filling was observed. Right cavity diameters were increased. The cardiac autonomic alterations were in favor of sympathetic hyperactivity. After a fish-catching diving competition in cold water, alterations suggesting dehydration, contraction in plasma volume and sympathetic hyperactivity were observed. Furthermore, enlargements of right cavities were in favor of right ventricular strains. Repeated apnea and swimming in cold water may account for these alterations.

Specific diving training-induced arterial circulation changes.

OBJECTIVE: Several stressors such as cold water immersion, hyperoxic exposure and decompression-induced circulating bubbles can alter arterial circulation after a dive. The aim of this study was to investigate the arterial modifications induced by a specific diving training including repeated hyperbaric exposures and physical training. METHOD: Arterial pressure measurement and pulse wave velocity (PWV) recordings were performed in 12 student military divers before and after 15 weeks' training. The results were compared with the same investigations performed in 12 non-diver healthy subjects. RESULTS: A decrease in systolic blood pressure and pulse pressure was observed at both upper and lower limbs in student military divers after the training. Non-significant decreases in both carotido-femoral PWV and carotido-pedal PWV were found after the training. When the pulse time transit was divided by the cardiac cycle length between two R peaks ((RR) interval), a significant increase was observed between the carotid and femoral sensors. On the other hand, some differences were noticed between military divers and controls. Controls and divers were matched appropriately according to age and height, although the divers had a higher aerobic capacity as well as lower resting heart rate and lower pulse wave velocity. CONCLUSION: In trained military subjects, a training which includes repeated diving exposures and endurance exercises leads to vascular modifications suggesting an increase in central arterial compliance. There was no sign of arterial alteration induced by repeated diving exposures.

Military diving training improved arterial compliance.

This study was aimed at investigating whether repeated SCUBA diving might induce long term cardiovascular and autonomic modifications. In 11 military mine clearance diving students, arterial compliance (ultrasound scan study of brachial artery and ratio of stroke volume to pulse pressure: SV/PP), resting spectral analyses of heart rate and blood pressure variability, and a cold pressor test were performed before and after a 15-week military diving training course. After the diving training, arterial compliance was improved, as indicated by the significant increase in brachial arterial compliance (from 24+/-10 to 37+/-14 ml.mmHg (-1)) and SV/PP (from 1.7+/-0.2 to 1.9+/-0.2 ml.mmHg (-1)), and by the significant decrease in systolic, diastolic and pulse pressures (from 130+/-8 to 120+/-7; from 71+/-4 to 67+/-4; and from 58+/-8 to 53+/-5 mmHg, respectively). The peak oxygen uptake increased significantly from 54.3+/-2.0 to 56.8+/-4.0 mL.kg (-1).min (-1). Finally, the vasoconstrictive response during the cold pressor test increased (p<0.05). These findings point to a positive effect of a 15-week military diving training course on vascular function, and for a concomitant development of some peripheral vascular acclimatization to cold.

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.

Pulmonary oedema in healthy SCUBA divers: new physiopathological pathways.

INTRODUCTION: The mechanism of immersion pulmonary oedema occurring in healthy divers is a matter of debate. Among consecutive injured divers admitted to our hyperbaric centre, we analysed prospective data about pulmonary oedema. METHOD: A total of 22 divers suffering from immersion pulmonary oedema without cardiac disease were included. The occurrence of events was compared to the diving conditions as assessed by diving-computer. Each patient underwent a clinical examination, laboratory tests, thoracic CT scan and echocardiography. RESULTS: The median age was 49 years, with a higher proportion of women, in comparison with the data of the French diving federation. The common feature was the occurrence of respiratory symptoms during the ascent after median dive duration of 29 min with strenuous exercise and/or psychological stress. Most of the dives were deep (37 msw-121 fsw) in cool water (15 degrees C-59 degrees F). The average inspired oxygen partial pressure was 0.99 bar. Progression was rapidly favourable, and the medical check-up after clinical recovery was normal. CONCLUSION: Immersion, body cooling, hyperoxia, increased hydrostatic pressure and strenuous exercise likely combine to induce pulmonary oedema in patients without cardiac disease. This study underlines new physiopathological tracks related to the frequent occurrence of symptoms noticed in the last part of the ascent and a higher incidence in women.