DEPENDENCE OF TISSUE OXYGEN ON OXYGEN DELIVERY

The viability of tissue flaps depends on adequate blood how and oxygen ation. To help ensure oxygen delivery, increased inspired oxygen is of ten provided, This study uses a porcine model to measure tissue oxygen (TPO2) in a muscle flap, in response to varying levels of inspired ox ygen concentration (FiO(2)). Six swine underwent the creation of a lat issimus dorsi island flap, An ultrasonic flow probe was used to monito r afferent flow through the thoracodorsal artery, and a 20-ga fluoresc ence-quenching optode was employed to monitor TPO2. Additional optodes were inserted in muscle of an ipsilateral hindlimb, and in the termin al ileum. Inspired oxygen concentration was varied from 15 to 100%, an d oxygen delivery variables measured. Analysis of variance and multipl e linear regression were used to determine which variables had the gre atest effect on TPO2. All three sites varied directly with inspired ox ygen concentration. Flap TPO2 had a strong dependence on FiO(2) and lo cal oxygen delivery (r(2) = 0.54). PaO2 and hemoglobin were the most s ignificant determinants of ileal submucosal TPO2 (r(2) = 0.65). A corr elation between average submucosal and flap TPO2 was observed (r > 0.9 , P < 0.05). We conclude that (1) muscle flap and bowel TPO2 vary dire ctly with inspired FiO(2), (2) changes in ileal submucosal TPO2 correl ate with those observed in muscle, and (3) monitoring of readily acces sible muscle TPO2 merits further investigation to evaluate the status of TPO2 in critical visceral beds. (C) 1996 Academic Press, Inc.