不同加压速率对大鼠高压空气暴露下生存时间的影响

Effects of continuous compression at different compressing rates on the survival time of rats exposed to hyperbaric air

目的：观察不同加压速率对大鼠高压空气暴露下生存时间的影响，探讨常压潜水服（atmospheric diving suit，ADS）固壳破损后可能的救援时间。方法24只健康雄性 SD 大鼠，以空气作为呼吸介质，以1 m／min 加压到120 m 后，高速组采用1 m／min 继续加压到300 m，中速组采用0．44 m／min的速率加到200 m 后采用0．21 m／min 的速率继续加压到300 m，低速组采用0．44 m／min 的速率加到200 m 后采用0．10 m／min 的速率加压到300 m。观察不同速率下动物耐受压力极值、惊厥潜伏期和生存时间。结果高速率组的动物死亡时压力极值[（242．50±26．77）]m 最高，惊厥潜伏期[（178．00± 1．93）]min 和生存时间[（247．75±14．86）]min 最短。与高速率组相比，中速率组和低速率组大鼠的耐受压力极值明显降低，惊厥潜伏期显著延长，生存时间明显延长，差异均有统计学意义（P ＜0．05）。与中速率组相比，低速率组大鼠的耐受压力极值和生存时间差异无统计学意义（P ＞0．05），但惊厥潜伏期延长（P ＜0．05）。随着加压速率减慢，大鼠死亡时的氧分压极值也降低，低速率组与高速率组相比，差异有统计学意义（P ＝0．001）；肺型氧中毒剂量单位（unit pulmonary toxic dose，UPTD）值则随加压速率减慢而增高，与高速率组相比，中速率组和低速率组的差异有统计学意义（P ＜0．05），但3组 UPTD 值尚在人体的最大允许值范围内。结论不大于1 m／min 的加压速率下，大鼠的空气高压耐受能力大约是深度200 m，时间200～320 min，人的耐受极限小于大鼠。因此，ADS 若发生相对慢的渗水，救援应立即展开，在压力升高到200 m 前尚在生存时间范围内，人员的生还几率较高。随着泄漏速率（压力升高速度）的增加，救援时间缩短。

Objective To observe the effects of continuous compression at different compressing rates on the survival time of rats exposed to hyperbaric air,and also to explore the possible time remained for the rescue of the diver following hard shell leakage of the atmospheric diving suit （ADS）.Methods Twenty -four male healthy SD rats were divided into 3 subgroups：the high compressing rate group,the moderate compressing rate group and the low compressing rate group.All the animals groups were compressed to a pressure of 120 m at a compression rate of 1 m/min.Then,the high compressing rate group was further compressed to a pressure of 300 m at a compression rate of 1 m/min,the moderate compressing rate group was first further compressed to a pressure of 200 m at a compression rate of 0.44 m/min and was finally compressed to a pressure of 300 m at＆amp;nbsp;a compression rate of 0.21 m/min,and the low compressing rate group was first further compressed to a pressure of 200 m at a compression rate of 0.44 m/min and was finally compressed to a pressure of 300 m at a compression rate of 0.1 m/min.Clinical manifestations,pressure tolerance limit,convulsion latency（CL）and survival time （ST）of the animals were closely observed.Results The pressure tolerance limit of the high compressing rate group,when the animals died,was the highest（242.50 ±26.77）m,the convulsion latency was（178.00 ±1.93）min and the survival time was the shortest （247.75 ± 14.86）min.As compared with that of the high compressing rate group,the pressure tolerance limits of the moderate compressing rate group and the low compressing rate group significantly decreased,convulsion latency and survival time were obviously prolonged,and statistical significance could be noted,when comparisons were made between them（P 〈0.05 or P 〈0.01）.When compared with the moderate compressing rate group,there was no statistical significance in the pressure tolerance limit and survival time for the low compressing rate group （P 〉0.05 ）,however, convulsion latency was prolonged（P 〈0.05）.With the decrease in compressing rate,oxygen partial pressure limits also decreased,when the animals died.And statistical significance could be seen,when comparisons were made between the low compressing rate group and the high compressing rate group（P =0.001）.The value of unit pulmonary toxic dose（UPTD）increased with the decrease in compressing rate.As compared with the high compressing rate group,statistical significance could be found in the moderate compressing rate group and the low compressing rate group（P 〈0.05 or P 〈0.01）.However,the UPTD values of the 3 groups were still within maximum human tolerance limits.Conclusions At the compressing rate lower than 1 m/min,the air pressure tolerance limit of the rat was about 200 m,the tolerance time was within 200 -320 min.The human pressure tolerance limit was lower than that of the animal.For this reason,in case of relatively low leakage of the ADS,rescue should be implemented immediately.When the increase in pressure （200 m）was still within the survival time,the survival probability was still relatively high.With the increase in the rate of pressure leakage,the time left for rescue would be obviously shortened.