Ostwald Ripening for Gas Bubbles and Decompression in Diving

The Ostwald ripening phenomenon for gas bubbles in a liquid consists mainly in gas transfer from smaller to larger bubbles. While the phenomenon itself is well known, the consequence of the temporal evolution of bubbles in the bloodstream in human physiology lacks deeper investigation.

In this work, a series of direct experiments was carried out in which the Ostwald ripening for air bubbles in a viscous fluid was reproduced. There, the time evolution of the bubbles' mean radius, number of bubbles, and radius size distribution was measured, where the initial bubble distribution behaves like a Tsallis (q-Weibull) distribution.

The results show the usual behavior of wet foam, where smaller bubbles disappear, whereas the larger bubbles, potentially dangerous for the diver, grow, and the number of bubbles decreases in time. On the other hand, a long-time power-law regime was found with an exponent smaller than that of the LSW (Lifshitz-Slyozov-Wagner) model, and the radius size distribution showed positive asymmetry throughout the experiment.

From the results obtained, it is presumed that such a bubble broadening effect could contribute, even minimally, to decompression illness: decompression sickness and arterial gas embolism. This conjecture is reinforced by the preliminary results of Ostwald broadening to RGBM (Reduced Gradient Bubble Model) decompression schedules for a closed-circuit rebreather (CCR) dive to 420 feet of seawater (fsw) (128 meters of seawater (msw)) with a 21/79 Heliox gas mixture, where the first decompression stops lengthening time thanks to Ostwald ripening is at the Pyle-type deep stop, a stop at the half bottom depth, 210 fsw (64 msw).