In vitro evidence of decompression bubble dynamics and gas exchange on the luminal aspect of blood vessels: Implications for size distribution of venous bubbles

Abstract

We found that lung surfactant leaks into the bloodstream, settling on the luminal aspect of blood vessels to create active hydrophobic spots (AHS). Nanobubbles formed by dissolved gas at these AHS are most probably the precursors of gas micronuclei and decompression bubbles. Sheep blood vessels stretched on microscope slides, and exposed under saline to hyperbaric pressure, were photographed following decompression. Photographs of an AHS from a pulmonary vein, containing large numbers of bubbles, were selected in 1-min sequences over a period of 7 min, starting 18 min after decompression from 1,013 kPa. This showed bubble detachment, coalescence and expansion, as well as competition for dissolved gas between bubbles. There was greater expansion of peripheral than of central bubbles. We suggest that the dynamics of decompression bubbles on the surface of the blood vessel may be the closest approximation to true decompression physiology, and as such can be used to assess and calibrate models of decompression bubbles. We further discuss the implications for bubble size in the venous circulation.

Keywords: active hydrophobic spot; blood vessel; gas micronuclei; nanobubbles.

Figure 1

(a) Photographs of bubbles at an active hydrophobic spot (AHS) on a pulmonary vein, over a period of 7 min, starting 18 min (time 0) from decompression. (b) Detachment of a large bubble (arrow) 1 s before time 0. (c) Coalescence of two bubbles (indicated by the arrow). The sudden increase in volume of the single bubble formed can be seen in the frame on the right

Figure 2

Time distribution of the first bubble to reach a diameter of 0.1 mm at each AHS. The line is hand drawn

Figure 3

Percentage of detached bubbles as a function of their diameter