Relationship of oxygen content to PO₂ for stabilized bubbles in the circulation: Theory

Stabilized bubbles can pass through capillary beds, recirculate for a few minutes or hours, and carry O₂ from the lungs to the tissues. Here, we develop the theory for the O₂ content-PO₂ relationship of bubbles and the alterations of the bubbles that are coupled to the O₂ transport. We provide examples for bubbles stabilized by a slowly permeating gas; bubbles stabilized by mechanical structures may behave similarly. Because there are two mechanisms for O₂ unloading (lowering of PO₂ and shrinkage), the bubbles release a large fraction of their O₂ content at high PO₂; when pure O₂ is breathed, one-half of the content of a 3-μm-radius bubble is released before PO₂ falls to 500 Torr. The possibility that stabilized bubbles could become a clinical tool for therapeutic transport of O₂ raises many issues to be investigated. The high-unloading PO₂ offers opportunities for delivering O₂ by diffusion to poorly perfused regions of the tissue but also presents a hazard of O₂ toxicity to perfused tissue.