Effect of combined recompression and air, oxygen, or heliox breathing on air bubbles in rat tissues

The fate of bubbles formed in tissues during the ascent from a real or simu lated air dive and subjected to therapeutic recompression has only been ind irectly inferred from theoretical modeling and clinical observations. We vi sually followed the resolution of micro air bubbles injected into adipose t issue, spinal white matter, muscle, and tendon of anesthetized rats recompr essed to and held at 284 kPa while rats breathed air, oxygen, heliox 80:20, or heliox 50:50. The rats underwent a prolonged hyperbaric air exposure be fore bubble injection and recompression. In all tissues, bubbles disappeare d faster during breathing of oxygen or heliox mixtures than during air brea thing. In some of the experiments, oxygen breathing caused a transient grow th of the bubbles. In spinal white matter, heliox 50:50 or oxygen breathing resulted in significantly faster bubble resolution than did heliox 80:20 b reathing. In conclusion, air bubbles in lipid and aqueous tissues shrink an d disappear faster during recompression during breathing of heliox mixtures or oxygen compared with air breathing. The clinical implication of these f indings might be that heliox 50:50 is the mixture of choice for the treatme nt of decompression sickness.