The oxygen optode: an improved method of assessing flap blood flow and viability

The ability of a newly developed, implantable PO2 electrode to detect vascular occlusion in an isolated skin flap model was evaluated. Cutaneous groin flaps, based on the superficial epigastric artery and vein, were raised in twelve rabbits. An optochemical, oxygen-sensing electrode (Oxygen Optode--InnerSpace, Inc.), was inserted in the subcutaneous tissue of each flap. Inspired oxygen, location of the probe, ambient temperature, and temperature of the isolated, pedicled flaps were controlled. After equilibration of the electrode in the flaps at baseline oxygen levels, selective, reversible occlusion of the artery, vein, and combined vascular pedicle was carried out. The tissue PO2 in the flaps were continuously monitored over the periods of vascular compromise and subsequent reperfusion. The rates of change in tissue PO2 over time (mean +/- SEM) following arterial, venous, or combined occlusion were not statistically different. The ability to confirm vascular compromise by challenging the organism with 100% inspired oxygen was also examined. A rise in tissue PO2 levels above baseline was noted on oxygen challenge with both artery and vein patent. At no time was a rise in tissue PO2 seen during oxygen challenge with arterial or combined arteriovenous occlusion. Measurements of tissue PO2 obtained by the Oxygen Optode are felt to reliably reflect vascular occlusion of the isolated epigastric skin flap perfusion in the rabbit model.