Identifying a site for maximum delivery of oxygen to transplanted cells

For in vivo cell implantation techniques to be successful, the energy and metabolic substrate requirement of the cells being grown must be met. Certain cells with high-energy requirements (e.g., hepatocytes, pancreatic island cells) experience a high degree of cell death after implantation due to a limited supply of oxygen. We proposed that the pleural cavity might be an oxygen-rich environment and hence an excellent site for cell implantation. To test the hypothesis that the delivery of oxygen to the pleural cavity is directly proportional to the inspired oxygen concentration we measured the pO₂ of saline instilled in the pleural cavity as compared to that of the peritoneal cavity. We postulated that the physiologic basis for any difference was the result of direct diffusion of oxygen into the pleural space across the alveoli. The study was conducted on sheep (n = 6), after induction of general anesthesia, in two phases, control and experimental. Saline was instilled into the peritoneal and pleural cavities via catheters, after equilibration at given FiO₂, the pO₂ of the paline aspirated from the two cavities was compared. In the experimental group, animals were sacrificed (no circulation) and ventilated. The same sequence of steps as in the control phase were repeated. In the control group, the pO₂ of saline aspirated from the pleural cavity approached the arterial pO₂ at all FiO₂ levels. The pO₂ of the peritoneal saline aspirate fell over time. In the experimental phase (no circulation), the pO₂ of the pleural cavity saline rose to >400 mmHg. We conclude that this is a result of direct diffusion and is a potential source of unlimited oxygen supply not dependent on vascular supply.