Abstract： Objective To observe the effect of hyperbaric oxygen(HBO) on the healing of penetrating skeletal muscle wound induced by fire arms coupled with seawater immersion,and to provide evidence for adjuvant HBO treatment of limb wounds induced by fire arms coupled with seawater immersion.Methods Eighteen adult hybrid dogs were randomly divided into the control group ( n =9) and the HBO group ( n =9).The gunshot wound and seawater immersion model was established by firing type 92 military pistol at the right hind limb of the dogs from a perpendicular height of 500 mm,then,were immersed in artificial seawater for 1 h and were given debridement,routine dressing change and antibiotic treatment.The HBO group received pure HBO therapy,one session a day for 75 minutes,for a succession of 14 days at a pressure of 0.22 MPa.The recovery time of diet and defensive behavior of the animals,the healing rates of wound surface on the 3rd,6th and 9th days,and the wound surface healing time from the 10th to 14th days following injury were monitored both in the control group and the HBO group.The dogs were sacrificed 14 days after injury.The scar pathology of the wounded muscular tissue was observed with naked eye,and samples from the wounded sites were collected for light and electron microscopy.Results The recovery time of diet and defensive behavior for the animals in the HBO group were obviously shorter than that of the control group(P ＜0.01 ).The wound surface healing rate for the HBO group was significantly higher than that of the control group(P ＜0.05).The wound surface healing time for the HBO group was obviously shorter than that of the control group( P ＜ 0.05 ).Under the light microcopy,the scar tissue could be observed in the primary wound track area in the animals of the HBO group.For the animals in the control group,the scar tissue and a mixture of granulation tissue could be observed.The healing process of the damaged tissue in the animals of the HBO group was obviously faster than that of the animals in the control group.Conclusions HBO had the effect of enhancing the healing of the gunshot injury coupled with seawater immersion.