Dependence of tissue oxygen on oxygen delivery

Abstract The viability of tissue flaps depends on adequate blood flow and oxygenation. To help ensure oxygen delivery, increased inspired oxygen is often provided. This study uses a porcine model to measure tissue oxygen (TPO 2 ) in a muscle flap, in response to varying levels of inspired oxygen concentration (FiO 2 ). Six swine underwent the creation of a latissimus dorsi island flap. An ultrasonic flow probe was used to monitor afferent flow through the thoracodorsal artery, and a 20-ga fluorescence-quenching optode was employed to monitor TPO 2 . Additional optodes were inserted in muscle of an ipsilateral hindlimb, and in the terminal ileum. Inspired oxygen concentration was varied from 15 to 100%, and oxygen delivery variables measured. Analysis of variance and multiple linear regression were used to determine which variables had the greatest effect on TPO 2 . All three sites varied directly with inspired oxygen concentration. Flap TPO 2 had a strong dependence on FiO 2 and local oxygen delivery ( r 2 = 0.54). PaO 2 and hemoglobin were the most significant determinants of ileal submucosal TPO 2 ( r 2 = 0.65). A correlation between average submucosal and flap TPO 2 was observed ( r > 0.9, P 2 vary directly with inspired FiO 2 , (2) changes in ileal submucosal TPO 2 correlate with those observed in muscle, and (3) monitoring of readily accessible muscle TPO 2 merits further investigation to evaluate the status of TPO 2 in critical visceral beds.