Objective: To compare the effect of two types of intermittent pressure on formation of pressure ulcer in rabbit hind limbs and to investigate the mechanism of gradually changed intermittent pressure produced by waves bed in the prevention of pressure ulcer.
Methods: Gracilis (3 cm2) in both hind limbs of 12 adult Japanese white rabbits were randomly loaded with gradually changed intermittent pressure (50-160 mm Hg, 1 mm Hg = 0.133 kPa) and sustained pressure (100 mmHg) serving as the experimental group and the control group, respectively. The experiment was terminated after 4 cycles, and a single cycle included 2 hours of compression and 30 minutes of compression-release. Blood velocity of hind limbs and blood perfusion of wound were detected by bidirectional Doppler blood flow detector and laser Doppler perfusion imaging detection system before compression and at every 10 minutes in compression-release period of each cycle (0, 10, 20 and 30 minutes). After the termination, gross observation of the wound was conducted, pathomorphological changes of tissues from compressed area were observed by HE staining, and contents of NO, malondialdehyde (MDA), and superoxide dismutase (SOD) in muscle tissue were measured using colorimetry method.
Results: No significant difference was evident between two groups in terms of blood flow velocity before compression (P > 0.05); the blood flow velocity of two groups decreased significantly at 0 minute in every compression-release period of each cycle, and no significant differences were noted between two groups (P > 0.05); the blood flow velocity of the experimental group was higher than that of the control group at 10, 20 and 30 minutes (P < 0.05). No significant difference was noted between two groups in terms of wound blood perfusion before compression (P > 0.05); the wound blood perfusion of two groups decreased significantly at 0 minute in every compression-release period of each cycle, and no significant differences were noted between two groups (P > 0.05); the difference between two groups was not significant at 10 minutes in the first cycle (P > 0.05), and the experimental group was higher than the control group at 20 and 30 minutes in the first cycle (P < 0.05). In the following 3 cycles, the recovery of perfusion in the experimental group was faster than that of the control group (P < 0.05). Gross observation showed the experimental group had less effusion than the control group. The experimental group had intact cutaneous appendage, less inflammatory cell infiltration, and no obvious ulcer formation, whereas the control group had obvious skin ulcer, depletion of cutaneous appendage, and more inflammatory cells infiltration. Significant differences were noted between two groups in terms of NO, MDA, and SOD content (P < 0.05).
Conclusion: Gradually changed intermittent pressure can maintain the blood perfusion of tissue, reduce ischemia-reperfusion injury and cell apoptosis, and prevent the formation of pressure ulcer.