Objective To explore animal model and evaluation indices of inhalation injury combined with decompression sickness(DSC),so as to lay a foundation for the studies on damage effect,mechanism,prevention,and military medical service of this disease.Methods A total of 16 SD rats with similar physiological states were selected and randomly divided into four groups,including control group,DCS group,smoke inhalation injury(SII)group,and combined injury group(DCS after SII induced by a self-made device).Arterial blood gas,wet-dry ratio of lung tissue(W/D),and inflammatory cytokines in bronchoalveolar lavage fluid(BALF)like interleukin(IL)-1β IL-6,and tumor necrosis factor-α(TNF-α)were measured at 24 hours after modeling.And pulmonary histopathological staining was performed.Results The partial pressure of oxygcn in the combined injury group was lower than those in the other groups,while the partial pressure of arterial oxygen in the combined injury group was higher than those in the other groups(P<0.05).The results of pulmonary histopathology showed the thickening of the interlobular septa and the leakage and massive accumulation of inflammatory cells.The symptoms of acute lung injury in the combined injury group were more severe than those in the DCS and SII groups.The W/D and inflammatory cytokines in the combined injury group were significantly higher than those in the DCS group and SII group(P<0.05).Conclusion The animal model of SII combined with DCS has been successfully established.Pulmonary injury in the combined injury model is more severe than that in the single injury models.

Objective:To build a mathematic model for calculating the heliox saturation diving decompression table.Methods:Based on the Haldane’s gas theory, this study analyzed the equilibrium condition of forces on the surface of bubbles in tissues to deduce the safety residence time of each decompression stop controlled by the safe excess pressure. Then, a calculating method of heliox saturation diving decompression table was obtained.Results:The decompression table calculated in this study has a higher desaturation efficiency compared with the British Royal Navy’s table; and it has a more reasonable decompression time distribution and better depth extrapolation compared with the US navy’s table. This table has been verified by more than 60 man-time (8 person times deeper than 300 msw) heliox saturation diving, and no decompression sickness occurred.Conclusion:The mathematic decompression model built in this study has the significance of determinacy in physics. It has many advantages in time distribution, depth extrapolation, and overall safety.

Objective:To evaluate the changes of cortisol and sIgA in serum and saliva of rats under different stresses and pressures, so as to provide a basis for screening non-invasive stress monitoring indicators in high-pressure working environment.Methods:A total of 54 rats were divided into six groups exposed to different air pressures of 0 kPa, 175 kPa, 350 kPa, 500 kPa, 600 kPa, and 700 kPa, respectively. According to different stress conditions, another 36 rats were divided into physiological stress group (PSSG), psychological stress group (PCSG), physiological and psychological stress group (PPSG), and blank group (BG), with 9 rats in each group. At the end of the experiment, serum sample was collected and supernatant was taken from the sublingual gland tissue homogenate. Cortisol and sIgA levels in saliva and serum were determined by radioimmunoassay and enzyme-linked immunosorbent assay (ELISA).Results:The concentrations of SIgA in group 500 kPa, 600 kPa, and 700 kPa were significantly different ( F=10.961, P<0.001; F=4.693, P=0.001; F=4.353, P=0.003). The serum cortisol levels in group 175 kPa, 350 kPa, and 600 kPa were significantly higher than that in group 0 kPa, while the serum cortisol level in group 350 kPa was significantly higher than those in group 500 kPa and 700 kPa. The cortisol concentrations of sublingual gland tissues in group 350 kPa and 700 kPa were significantly higher than those in group 0 kPa, 500 kPa, and 600 kPa. Under different stress conditions, serum sIgA concentrations in PCSG, PSSG, and PPSG were significantly lower than that in BG ( F=4.852, P=0.007; F=4.918, P=0.007; F=3.967, P=0.017). The levels of serum and sublingual cortisol in PCSG and PPSG were significantly higher than those in BG, while the levels of serum and sublingual cortisol in PSSG were significantly lower than those in PCSG. Relevant research results showed that the changes of salivary gland cortisol and serum cortisol were positively correlated under different stress conditions ( r=0.609, P<0.01). Conclusion:Cortisol as a stress monitoring indicator has good effectiveness, and using saliva as an indicator to monitor stress under high pressure environment has a certain degree of feasibility.

Objective:To observe the changes of plasma nitric oxide (NO) and desmosine (DES) concentrations in animals under different decompression pressure loads, and to explore the role of NO and DES in quantitative evaluation of diving decompression injury.Methods:A total of 50 male SD rats were divided into five groups with 10 rats in each group by the random table method. Rats in Group 1 were not pressurized and were given air ventilation, and left the cabin after 120 min; after pressurized to 70 m for 70 min, 40 rats in the other four groups were decompressed at a constant rate to the normal pressure in 40 min (Group 2), 30 min (Group 3), 20 min (Group 4) and 10 min (Group 5), respectively. The changes of plasma NO and DES concentrations in rats after leaving the cabin were observed. A total of 40 male rabbits were divided into four groups with 10 rabbits in each group by the random table method. The rabbits were used to simulate fast buoyancy ascent escape from the depth of 150 m and the compression pressure doubled every four seconds. The four groups were decompressed at a constant rate of 6 m/s after being given different bottom time, i. e., 4 s (Group 1), 60 s (Group 2), 180 s (Group 3), and 300 s (Group 4). The changes of plasma NO and DES concentrations in the rabbits after leaving the cabin were analyzed.Results:Compared with the rats in the Group 1, the plasma NO and DES concentrations of the rats of the Group 5 significantly increased, with statistically significant differences ( P<0.05 or P<0.01), and the plasma DES concentration of the rats in the Group 4 also increased, with a statistically significant difference ( P<0.05). The plasma NO and DES concentrations in rats were positively correlated with the reciprocal of the decompression time at a constant rate (NO: r=0.683, P<0.01; DES: r=0.535, P<0.01) and showed significant linear regression relationships (NO: r2=0.467, P<0.01; DES: r2=0.287, P<0.01). Compared with the values before escape, the plasma NO concentrations in the rabbits of the Group 3 and 4 increased significantly, with statistically significant differences ( P<0.01), and the plasma DES concentrations in all four rabbit groups increased significantly, with statistically significant differences ( P<0.01). After leaving the cabin, compared with the rabbits in the Group 1, the plasma NO and DES concentrations in rabbits of the Group 3 and 4 increased significantly, with statistically significant differences (NO: P<0.05 or P<0.01; DES: P<0.01). After leaving the cabin, the plasma NO and DES concentrations in rabbits were positively correlated with the bottom time (NO: r=0.672, P<0.01; DES: r=0.702, P<0.01)and showed significant linear relationships (NO: r2=0.452, P<0.01; DES: r2=0.493, P<0.01). Conclusion:The plasma NO and DES concentrations can quantitatively indicate the damage caused by decompression pressure loads, which makes it possible to design decompression protocol and safety evaluation. The severity of decompression injuries is linearly related to the reciprocal of decompression time (or rate) that determines the decompression pressure load, which have reference value for the decompression rate control in the theoretical model of decompression.

Objective:To build a mathematic model for calculating the heliox saturation diving decompression table.Methods:Based on the Haldane’s gas theory, this study analyzed the equilibrium condition of forces on the surface of bubbles in tissues to deduce the safety residence time of each decompression stop controlled by the safe excess pressure. Then, a calculating method of heliox saturation diving decompression table was obtained.Results:The decompression table calculated in this study has a higher desaturation efficiency compared with the British Royal Navy’s table; and it has a more reasonable decompression time distribution and better depth extrapolation compared with the US navy’s table. This table has been verified by more than 60 man-time (8 person times deeper than 300 msw) heliox saturation diving, and no decompression sickness occurred.Conclusion:The mathematic decompression model built in this study has the significance of determinacy in physics. It has many advantages in time distribution, depth extrapolation, and overall safety.

Objective:To evaluate the changes of cortisol and sIgA in serum and saliva of rats under different stresses and pressures, so as to provide a basis for screening non-invasive stress monitoring indicators in high-pressure working environment.Methods:A total of 54 rats were divided into six groups exposed to different air pressures of 0 kPa, 175 kPa, 350 kPa, 500 kPa, 600 kPa, and 700 kPa, respectively. According to different stress conditions, another 36 rats were divided into physiological stress group (PSSG), psychological stress group (PCSG), physiological and psychological stress group (PPSG), and blank group (BG), with 9 rats in each group. At the end of the experiment, serum sample was collected and supernatant was taken from the sublingual gland tissue homogenate. Cortisol and sIgA levels in saliva and serum were determined by radioimmunoassay and enzyme-linked immunosorbent assay (ELISA).Results:The concentrations of SIgA in group 500 kPa, 600 kPa, and 700 kPa were significantly different ( F=10.961, P<0.001; F=4.693, P=0.001; F=4.353, P=0.003). The serum cortisol levels in group 175 kPa, 350 kPa, and 600 kPa were significantly higher than that in group 0 kPa, while the serum cortisol level in group 350 kPa was significantly higher than those in group 500 kPa and 700 kPa. The cortisol concentrations of sublingual gland tissues in group 350 kPa and 700 kPa were significantly higher than those in group 0 kPa, 500 kPa, and 600 kPa. Under different stress conditions, serum sIgA concentrations in PCSG, PSSG, and PPSG were significantly lower than that in BG ( F=4.852, P=0.007; F=4.918, P=0.007; F=3.967, P=0.017). The levels of serum and sublingual cortisol in PCSG and PPSG were significantly higher than those in BG, while the levels of serum and sublingual cortisol in PSSG were significantly lower than those in PCSG. Relevant research results showed that the changes of salivary gland cortisol and serum cortisol were positively correlated under different stress conditions ( r=0.609, P<0.01). Conclusion:Cortisol as a stress monitoring indicator has good effectiveness, and using saliva as an indicator to monitor stress under high pressure environment has a certain degree of feasibility.

Objective:To observe the changes of plasma nitric oxide (NO) and desmosine (DES) concentrations in animals under different decompression pressure loads, and to explore the role of NO and DES in quantitative evaluation of diving decompression injury.Methods:A total of 50 male SD rats were divided into five groups with 10 rats in each group by the random table method. Rats in Group 1 were not pressurized and were given air ventilation, and left the cabin after 120 min; after pressurized to 70 m for 70 min, 40 rats in the other four groups were decompressed at a constant rate to the normal pressure in 40 min (Group 2), 30 min (Group 3), 20 min (Group 4) and 10 min (Group 5), respectively. The changes of plasma NO and DES concentrations in rats after leaving the cabin were observed. A total of 40 male rabbits were divided into four groups with 10 rabbits in each group by the random table method. The rabbits were used to simulate fast buoyancy ascent escape from the depth of 150 m and the compression pressure doubled every four seconds. The four groups were decompressed at a constant rate of 6 m/s after being given different bottom time, i. e., 4 s (Group 1), 60 s (Group 2), 180 s (Group 3), and 300 s (Group 4). The changes of plasma NO and DES concentrations in the rabbits after leaving the cabin were analyzed.Results:Compared with the rats in the Group 1, the plasma NO and DES concentrations of the rats of the Group 5 significantly increased, with statistically significant differences ( P<0.05 or P<0.01), and the plasma DES concentration of the rats in the Group 4 also increased, with a statistically significant difference ( P<0.05). The plasma NO and DES concentrations in rats were positively correlated with the reciprocal of the decompression time at a constant rate (NO: r=0.683, P<0.01; DES: r=0.535, P<0.01) and showed significant linear regression relationships (NO: r2=0.467, P<0.01; DES: r2=0.287, P<0.01). Compared with the values before escape, the plasma NO concentrations in the rabbits of the Group 3 and 4 increased significantly, with statistically significant differences ( P<0.01), and the plasma DES concentrations in all four rabbit groups increased significantly, with statistically significant differences ( P<0.01). After leaving the cabin, compared with the rabbits in the Group 1, the plasma NO and DES concentrations in rabbits of the Group 3 and 4 increased significantly, with statistically significant differences (NO: P<0.05 or P<0.01; DES: P<0.01). After leaving the cabin, the plasma NO and DES concentrations in rabbits were positively correlated with the bottom time (NO: r=0.672, P<0.01; DES: r=0.702, P<0.01)and showed significant linear relationships (NO: r2=0.452, P<0.01; DES: r2=0.493, P<0.01). Conclusion:The plasma NO and DES concentrations can quantitatively indicate the damage caused by decompression pressure loads, which makes it possible to design decompression protocol and safety evaluation. The severity of decompression injuries is linearly related to the reciprocal of decompression time (or rate) that determines the decompression pressure load, which have reference value for the decompression rate control in the theoretical model of decompression.

Objective:To evaluate the effects of different high pressure on the behavior and physiological indexes of hypothalamic-pituitary-adrenal axis (HPA) in rats, so as to provide a theoretical basis for the stress protection in decompression process.Methods:The rats were divided into four groups according to the random number table method and were separately exposed to air pressure of 0 kPa, 170 kPa, 350 kPa and 700 kPa for 60 mins and given decompression for 45 mins. The behaviors of rats were analyzed by animal open field method and video analysis system of the open field immediately after they were taken from the air pressure chamber, and the contents of adrenocorticotrophic hormone (ACTH) and glucocorticoid (GC) in the serum were measured by the enzyme-linked immunosorbent assay (ELISA).Results:Under different pressure, compared with the 0 kPa group, the total distance traveled by the rats ( F=3.354), the average traveling speed ( F=3.358), the number of standing times and standing time duration ( F=3.739; F=33.332) of the rats in the other 3 groups decreased significantly. The distance traveled in the corner of the 175 kPa group and the 700 kPa group decreased significantly ( F=3.532), while their cleaning time significantly increased ( F=4.581). The standing times and the cleaning time of the 350 kPa group were significantly less than those of the 700 kPa group. All the differences above showed statistical significance ( P<0.05). After exposure to different pressure, the ACTH level of the 175 kPa group was higher than those of the 0 kPa group and the 350 kPa group ( F=5.309) with statistical significance ( P<0.05). The GC level of the 0 kPa group was significantly lower than those of the other 3 groups, and the GC level of the 700 kPa group was especially lower than that of the 175 kPa group, with statistically significant difference ( P<0.05). Conclusion:High pressure exposure at all levels can cause definite stress reaction, and the stress reactions do not correlate with the pressure gradient. Within the physiological bearable range of stress under high pressure, the individual stress level may present a certain steady state. The individual′s behavioral response, ACTH and GC levels may be used as indicators for stress monitoring.

Objective:To evaluate the effects of different high pressure on the behavior and physiological indexes of hypothalamic-pituitary-adrenal axis (HPA) in rats, so as to provide a theoretical basis for the stress protection in decompression process.Methods:The rats were divided into four groups according to the random number table method and were separately exposed to air pressure of 0 kPa, 170 kPa, 350 kPa and 700 kPa for 60 mins and given decompression for 45 mins. The behaviors of rats were analyzed by animal open field method and video analysis system of the open field immediately after they were taken from the air pressure chamber, and the contents of adrenocorticotrophic hormone (ACTH) and glucocorticoid (GC) in the serum were measured by the enzyme-linked immunosorbent assay (ELISA).Results:Under different pressure, compared with the 0 kPa group, the total distance traveled by the rats ( F=3.354), the average traveling speed ( F=3.358), the number of standing times and standing time duration ( F=3.739; F=33.332) of the rats in the other 3 groups decreased significantly. The distance traveled in the corner of the 175 kPa group and the 700 kPa group decreased significantly ( F=3.532), while their cleaning time significantly increased ( F=4.581). The standing times and the cleaning time of the 350 kPa group were significantly less than those of the 700 kPa group. All the differences above showed statistical significance ( P<0.05). After exposure to different pressure, the ACTH level of the 175 kPa group was higher than those of the 0 kPa group and the 350 kPa group ( F=5.309) with statistical significance ( P<0.05). The GC level of the 0 kPa group was significantly lower than those of the other 3 groups, and the GC level of the 700 kPa group was especially lower than that of the 175 kPa group, with statistically significant difference ( P<0.05). Conclusion:High pressure exposure at all levels can cause definite stress reaction, and the stress reactions do not correlate with the pressure gradient. Within the physiological bearable range of stress under high pressure, the individual stress level may present a certain steady state. The individual′s behavioral response, ACTH and GC levels may be used as indicators for stress monitoring.

OBJECTIVETo investigate the effects of simulated nitrogen-oxygen saturation exposure at a water depth of 50 m on the expression of inflammatory mediators including interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-alpha (TNF-α) in the external auditory canal (EAC) of rabbits.

METHODSTwo batches of New Zealand rabbits were exposed to nitrogen-oxygen saturated at a water depth of 50 m. After exposure, the epithelial tissue in the EAC was analyzed using hematoxylin-eosin (HE) staining, and the changes in expression of inflammatory mediators including IL-6, IL-10, and TNF-α in the EAC of rabbits were determined by real-time polymerase chain reaction (PCR).

RESULTSAccording to the result of HE staining, more inflammatory cell infiltration, small vascular congestion, and mucosal edema in the EAC of rabbits were observed in the exposure group than in the control group. Additionally, compared with the control group, the exposure group had increased expression of IL-6 and TNF-α and reduced expression of IL-10 in the EAC of rabbits according to the result of real-time PCR.

CONCLUSIONThe nitrogen-oxygen saturation exposure at a water depth of 50 m can cause inflammatory injuries in the EAC of rabbits. The mechanism may be associated with increased expression of IL-6 and TNF-α and reduced expression of IL-10.

Animals ; Disease Models, Animal ; Ear Canal ; physiopathology ; Environmental Exposure ; adverse effects ; Inflammation Mediators ; metabolism ; Interleukin-10 ; metabolism ; Interleukin-6 ; metabolism ; Nitrogen ; adverse effects ; Oxygen ; adverse effects ; Rabbits ; Tumor Necrosis Factor-alpha ; metabolism ; Water ; adverse effects