Hemodynamic Changes Induced by Recreational Scuba Diving: Discussion

Hemodynamic Changes Induced by Recreational Scuba Diving: DiscussionWe emphasize that our study was conducted in actual diving conditions because more bubbling has been reported when the dives were performed in the open sea rather than when they were performed in hyperbaric chambers. Furthermore, during water immersion several modifications including hemodynamic, neuroendocrine, and autonomic activities changes have been demonstrated. Consequently, hemodynamic modifications should be very different after scuba diving when compared with dry hyperbaric exposures.
The diving profile studied is commonly performed by recreational divers but generates a rather important bubble grade in all volunteers. Indeed, a grade 3 was found in 7 of 10 divers 1 h after surfacing.
The population studied is representative of the population of recreational divers. Experienced divers with an average age of 44 years and a mean body mass index of 25 ± 3 were studied. Eight of 10 subjects did not practice any sport activities if not scuba diving. The incidence of individual factors as age, adiposity, and physical fitness on bubble formation is recognized. Thus, characteristics of the population studied may be responsible for the important bubble production.

A significantly reduced SV was found by our hemodynamic study 1 h after diving. A decrease in cardiac preload, a decrease in myocardial contractility, or an increase in cardiac afterload could explain this change.
Cardiac contractility remained normal after diving with preservation of LV %FS. Mean values for systolic and diastolic BP remained unchanged, and ventricular diameters were not enlarged. So, the hypothesis of an increase in LV afterload was low. However, a reduction in LV preload was evidenced by the reduction in LA diameter, LVEDD, and LVESD. This reduction in cardiac preload may be attributed to a contraction in plasma volume. Indeed, in previous studies,’ the loss of the plasma volume and resulting hemoconcentration have been demonstrated either in subjects after a single dive, repeated dives, or periods of daily diving. The plasma volume loss could be induced by environmental constraints.

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