Objective To quantitatively evaluate the effect of 2 types of pressures induced injury by using threedimensional (3D) reconstruction of rats loaded tibial is anterior muscle from two-dimensional (2D) image of serial histological sections. Methods Twenty female or male Sprague Dawley rats, aged 10-12 weeks and weighing 280-300 g, were randomlydivided into experimental group (n=10) and control group (n=10). The random side of tibial is anterior muscle was givenintermittent gradient (8.0-21.3 kPa) and sustained (13.3 kPa) pressure in 0.12 cm2 area in experimental group and controlgroup, respectively; the experiment was terminated and the general condition of rats was observed after 3 cycles, and a single cycle included 2 hours of compression and 30 minutes of release. The general observations of pressed skin and tibial is anterior muscle were done after 24 hours of pressure rel ief, and the tibial is anterior muscle was harvested integrally from the loaded side, then made into interval 4 μm serial sections. After HE staining, 2D images were obtained. Necrosis and injury areas were distinguished by Image Pro Plus (IPP) 6.0 software and image registration was conducted by Photoshop 8.0.1 after 2D panorama images acquired by digital microscope (× 40) and IPP mosaic software. 3D reconstruction was establ ished via data processing using Mimics 10.1 software so as to get the volume, the surface area, and 3D images of the whole piece of tibial is anterior muscle and injury areas respectively. Results All rats of 2 groups survived till experiment terminated and no skin ulcers occurred after 24 hours. Edema and indentation were observed on press side skin and tibial is anterior muscles of 2 groups, fadeless maroon area was observed in control group. A total of 994 sl ices were obtained from 20 samples of tibial is anterior muscles. 3D images suggested that injury of control group was severe, which penetrated the whole piece of tibial is anterior muscle and expandedalong the tibia bony prominence. By contrast, injury of experimental group was less, but had similar width to the contact surface of indentor. There was no significant difference in the volume and the surface area of tibial is anterior muscle between 2 groups (P gt; 0.05), while the injury volume and the injury surface area were significantly smaller in experimental group than in control group (P lt; 0.05). Conclusion 3D reconstruction is an effective method to quantitatively evaluate pathological changes inside the integrity tissue and can provide the visual basis for the mechanical property distributed in the loaded muscle. Intermittent gradient pressure can reduce deep tissue injury.
Objective To compare the effect of two types of intermittent pressure on formation of pressure ulcer in rabbit hind l imbs and to investigate the mechanism of gradually changed intermittent pressure produced by waves bed in the prevention of pressure ulcer. Methods Gracil is (3 cm2) in both hind l imbs of 12 adult Japanese white rabbits were randomlyloaded 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 l imbs 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 gt; 0.05); the blood flow velocity of two groups decreased significantly at 0 minute in every compressionrelease period of each cycle, and no significant differences were noted between two groups (P gt; 0.05); the blood flow velocity of theexperimental group was higher than that of the control group at 10, 20 and 30 minutes (P lt; 0.05). No significant difference was noted between two groups in terms of wound blood perfusion before compression (P gt; 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 gt; 0.05); the difference between two groups was not significant at 10 minutes in the first cycle (P gt; 0.05), and the experimental group was higher than the control group at 20 and 30 minutes in the first cycle (P lt; 0.05). In the following 3 cycles, the recovery of perfusion in the experimental group was faster than that of the control group (P lt; 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 lt; 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.