The Effect of Hyperbaric Oxygen Therapy on the Delay Procedure

Hyperbaric oxygen therapy in wound healing in mice

ABSTRACT We investigated the local and systemic effects of hyperbaric oxygen therapy in BALB/C mice, exposed to two different exposure times, under 2.4 atmosphere (ATM). Fifteen animals were divided into three groups (GI, GII and Control) and underwent a surgical excision of a skin fragment of approximately one square centimeter of the dorsal region. The wounds were treated and monitored for 21 days. In the control group, the wound was cleaned once a day with sterile 0.9% NaCl solution. GI and GII mice were submitted to daily hyperbaric oxygen therapy of 30 or 60minutes sessions, respectively. The wounds were photographed every three days and their surfaces were analyzed by an image analyzer. At 21 days, all animals were euthanatized for histopathological analysis of the skin, lungs and liver in order to identify eventual alterations in wound healing or in the analyzed organs. Animals belonging to GI showed a faster skin wound healing in comparison to the other groups. Animals from GII, however, showed a delayed wound healing process and exhibited lung and microcirculatory alterations. These findings allow us to conclude that the exposure time to the oxygen in hyperbaric environment is crucial and can help or disturb skin wound healing or even be deleterious to other organs.

Combination of vascular endothelial growth factor-loaded microspheres and hyperbaric oxygen on random skin flap survival in rats

The present study aimed to investigate the role of hyperbaric oxygen (HBO) and treatment with vascular endothelial growth factor (VEGF)-loaded microspheres, and HBO plus VEGF on the survival of random skin flaps in rats. The modified McFarlane flap model was established in 40 rats and evaluated within four groups: VEGF (n=10), HBO (n=10), HBO plus VEGF (n=10) and controls (n=10). Seven days following treatment, the necrotic area of the flap was measured. The specimens were stained with hematoxylin and eosin for histological analysis. Immunohistochemical staining was used to analyze the positive expression levels of VEGF. The percentages of necrosis of the skin flaps in all groups were: 49.66±2.64% in controls, 26.85±1.77% in VEGF, 28.27±2.21% in HBO and 10.44±2.48% in the combination group. Histological analysis demonstrated angiogenesis with mean vessel density per mm² in the groups were: 16.68±2.69 in controls, 22.96±3.29 in VEGF, 24.74±3.19 in HBO and 34.81±3.93 in the combination group. The expression of VEGF of the controls, VEGF, HBO and the combination group were 28.33±4.98, 52.54±4.55, 49.32±4.62 and 78.97±4.90 integral absorbance, respectively. For all measurements, the combination group showed greater improvement in random skin flap survival than others (P<0.05). No significant difference was detected between the VEGF and HBO group. The control group exhibited lower survival rates compared with the other groups (P<0.05). Combination of VEGF and HBO improved random skin flap survival compared with the effect of VEGF or HBO alone, suggesting these two agents exhibited a synergistic effect.

Action of hyperbaric oxygenation in the rat skin flap

PURPOSE

To evaluate the morphology, necrotic area and collagen content in skin flaps of rats subjected to hyperbaric oxygenation (HBO).

METHODS

Forty adult rats were divided into four groups: GEC - epilated; GE/HBO - epilated subjected to HBO; GER - epilated submitted to skin flap (2 cm in width /8 cm length in the dorsal area) and GER/HBO - epilated, subjected to skin flap and HBO. HBO (2.4 ATA) was performed for two hours during seven consecutive days. In the eighth day, the rats were anesthetized and the skin flaps were removed and separated into three portions, relative to pedicle fixation. The material fixed in 10% formalin was processed for paraffin embedding; sections were stained by H.E and subjected to picrosirius-red method. The slides examined under light microscopy for evaluation of the collagen content in polarized light microscope and ImageLab(r) software (Bio-Rad).

RESULTS

The data showed larger area of necrosis and lower levels of collagen in the three regions of the GER group, whereas in the GER/HBO group the collagen content was similar to the GEC and GE/HBO groups.

CONCLUSION

Hyperbaric oxygenation reduced the area of necrosis and preserved the morphology and collagen content in skin flaps of rats.

Effects of stromal cell derived factor-1 and CXCR4 on the promotion of neovascularization by hyperbaric oxygen treatment in skin flaps

Hyperbaric oxygen (HBO) is known to increase the survival of skin flaps by promoting neovascularization; however, the detailed mechanisms involved are not fully understood. In the present study, we aimed to characterize the effects of HBO treatment on neovascularization and skin flap survival. We also analyzed the mechanisms associated with the expression of angiogenic molecules, such as stromal cell derived factor-1 (SDF‑1) and its specific receptor CXCR4, to assess the effects of SDF-1 and CXCR4 on the promotion of neovascularization by HBO treatment in skin flaps. The epigastric pedicle skin flap model was established in rats that were randomly divided into the following groups: i) sham‑operated (SH group); ii) ischemia followed by reperfusion and analysis on the third and fifth day (IR3d and IR5d groups, respectively) postoperatively; iii) ischemia followed by reperfusion, HBO treatment and analysis on the third and fifth day (HBO3d and HBO5d groups, respectively) postoperatively. In the two HBO groups, animals received 1 h of HBO treatment in a 2.0 ATA chamber with 100% O2 twice per day for 3 days and then daily for 2 consecutive days following surgery. On the postoperative third and fifth day, skin flap survival measurement, histological analysis, immunohistochemical staining and western blotting for SDF‑1 and CXCR4 expression, were performed. Compared with those of the IR groups, skin flap survival, microvessel density (MVD) and expression of SDF‑1 and CXCR4 proteins were significantly increased in the HBO groups. Pearson's correlation analysis demonstrated a positive correlation between MVD and the high expression of SDF‑1 and CXCR4 following HBO treatment. Results of this study suggested that the effects of HBO treatment in promoting neovascularization may be explained by the upregulation of SDF‑1 and CXCR4 expression in the skin flaps of rats.

Effects of hyperbaric oxygen and N-acetylcysteine in survival of random pattern skin flaps in rats

OBJECTIVE

Our aim is to investigate the role of HBO (hyperbaric oxygen), NAC (N-acetylcysteine), and HBO plus NAC on the necrosis area of random rat's skin flaps of a modified McFarlane flap design.

MATERIALS AND METHODS

Thirty-two male Wistar rats were randomly divided into four groups: G-S (sham: n = 8), G-NAC (NAC: n = 8), G-HBO (HBO: n = 8), and G-HN (HBO plus NAC: n = 8). A rectangular skin flap (2 × 8 cm(2)) was dissected from the muscular dorsal layer, preserving the cranial pedicle. Polyethylene film was placed over the muscular layer and an interrupted 3.0 nylon suture was employed to fix the flap into the original place. On the eighth day, full-thickness biopsy samples (2 × 1 cm(2)) were collected from the proximal, middle, and cranial areas of the skin flap, and in a site away from the flap labelled as the control area.

RESULTS

The measurements of necrotic areas in the groups were 18.3% in G-S, 24.3% in G-NAC, 12.6% in G-HBO, and 14.9% in G-HN. Significant difference was observed between the groups G-HBO and G-HN as well as G-NAC.

CONCLUSION

HBO is associated with reduced area of necrosis of skin flap. The G-NAC group was associated with poor results when examined in isolation. The association between HBO and NAC did not produce favourable results with respect to the use of HBO alone. These findings suggest that the diffusion of oxygen through the interstitial space was the determining factor of more favourable results of HBO.

Is HBOT treatment effective in recovering zone of stasis? An experimental immunohistochemical study

Studies aimed at recovering the zone of stasis are one of the major issues of experimental burn studies. Hypoxia and oedema at that zone may cause irreversible changes. Due to anti-oedematous and antihypoxic effects of hyperbaric oxygen treatment (HBOT), it may be beneficial in recovering the zone of stasis. We performed an experimental study using 20 Sprague-Dawley rats, each weighing 350-450 g. The rats were first divided into two groups as 24h and 5 days. Subsequently, control and treatment groups (five rats in each group) were formed. For burn wounds, we used the burn comb model, which was described by Regas and Ehrlich. In the treatment group, 2.5 ATA HBOT was applied for 90 min twice daily. A 0.8-cm punch biopsy was performed and samples for histological examination were taken from the centre of burn area. The rats were sacrificed by administering '3 mci technetium-99m methoxy butyl nitrite' ((99)Tc(m) MIBI) through the femoral vein. Biopsy materials were evaluated by histological and immunohistochemical methods. Dorsal skin fragment, excised to 1cm margin, was imaged by scintigraphic measurements with a gamma camera. Wet and dry weight measurements of excised skin fragments were taken. As a result, HBOT showed a positive effect at the cellular level in the first 24h. It increased recovery potential by augmenting neovascularisation and decreasing oedema in the 5-day group.