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-microns-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 highunloading 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.