Fig. 4. Tissue oxygen tension measured by Clark probes in the control skin and the ipsilateral and contralateral flap skin. The bar graph represents mean ± SD in the nondiluted control group (hatched bars) and during graded normovolemic hemodilution (solid bars). The line graph represents the expected change in tissue oxygen tension related to hemoglobin concentration. F and P  are given for the regression of tissue oxygen tension on hemoglobin squared and hemoglobin.