Effects of ischemia on ulcer wound healing: a new model in the rabbit ear

To study the effects of alteration of blood flow on wound healing in rabbit ear ulcers, two models were designed that produced maximum ischemia and maximum congestion, respectively, with complete survival of the ear by selective division of one or more of three arteries or veins and circumferential incisions. After selection of the best models from six variations, tissue perfusion was measured indirectly by venous oxygen tension, dermofluorometry, pulse oximetry, and skin temperature. Wound healing was measured seven days after creating 6-mm surgical ulcers. The tissue oxygen tension calculated from the venous oxygen tension fell to 30 mm Hg through days 1, 3, and 7 in the ischemic ears, and skin temperature and blood flow measured by dermofluorometry were similarly affected. However, there was no evidence of significant change in tissue perfusion except increased skin temperature in the congested ears. None of the ischemic wounds were epithelialized completely, but half of the control and congested wounds were. The granulation tissue formation was decreased (39% of the area versus 63% of the area) and the infection rate was increased (20% versus 2%) significantly in the ischemic wounds compared with the control wounds but not in the congested wounds. The ischemic ulcer model is reproducible and quantifiable and is potentially a useful model for examining agents to improve ulcer healing where blood flow is decreased. The congestion model showed no significant changes in blood flow or wound healing.