OBJECTIVETo observe the effect of different time windows and interventions on skin pressure ulcers and ischemia-reperfusion (I/R) injury in rats.

METHODSSixty?eight SD rats were randomly divided into blank control group (n=4) and model group (n=64). The rats in the model group were randomly divided into group A (n=32) without intervention and group B (n=32) with post?conditioning. The degree of skin compression, neutrophil infiltration and serum levels of free radicals were observed in the rats after compression for 2, 4, 6, and 8 h (8 rats at each time point).

RESULTSA significant difference was found in the severity of skin damage among the control group, group A, and group B (P=0.001), and the injury was milder in group B than in group A. Severe skin lesions occurred in 2 rats after skin compression for 6 h, as compared with 6 after compression for 8 h (P=0.043), but in none of the rats after compression for 2 or 4. Seventeen rats in group B and 15 in group A showed grade 1 neutrophil infiltration in the skin lesions, and 8 rats in group B and 10 in group A showed grade II neutrophil infiltration (P=0.002). Neutrophil infiltration was the mildest in rats with a 2?h compression, and exacerbated progressively and significantly as the compression time extended (P=0.027). With the prolongation of the intervention time, the rats in both groups A and B showed decreased SOD and increased MDA and NO levels, and overall the I/R injury was milder in 2? and 4?h compression groups than in 6? and 8?h compression groups. The level of serum SOD was significantly higher and MDA and NO levels were significantly higher in group B than in group A (P<0.05).

CONCLUSIONIschemic post?conditioning can relieve I/R injury in acute pressure ulcer in rats. The effective time window for intervention is within 6 h of ischemia, and the effect of ischemic post-conditioning is optimal within 2 h. Ischemic post?conditioning can alleviate free radical injury and inflammation caused by I/R injury.