[Discussion on the relationship between the disposal time of hypobaric oxygen chamber and the establishment of rat cardiac arrest model at high altitude].

Objective: To establish the rat cardiac arrest model in high-altitude hypobaric hypoxia environment, and to explore the effect of the treatment time in the hypobaric oxygen chamber on the reproduction of high-altitude rat cardiac arrest model.

Methods: SPF grade healthy male Sprague-Dawley (SD) rats were used as observation subjects. The experiment was conducted in two different altitude areas. The rats from the Plateau Branch of Institute of Cardiopulmonary and Cerebral Resuscitation of Sun Yat-sen University (Xining, Qinghai) were weighed and numbered, and they were placed in a hypobaric oxygen chamber (simulated altitude of 3 000 meters, speed of ascent and descent of 15 m/min, temperature of 20 centigrade, cabin pressure of 69.5 kPa, cabin oxygen pressure of 14.5 kPa). After 30 days of feeding, the rats were obtained according to random number table method, and the cardiac arrest model was established by asphyxia method as the 30-day hypobaric hypoxia group. After 60 days of feeding, rats were randomly selected again, and the cardiac arrest model was established as the 60-day hypobaric hypoxia group. Thirty rats were randomly selected from the Institute of Cardiopulmonary Cerebral Resuscitation at Sun Yat-sen University (Guangzhou, Guangdong) by the same method, and the cardiac arrest model was established as the plain control group. The differences in the body weight of rat modeling precursors and the induction time of asphyxia during the modeling process among different groups were compared.

Results: Finally, cardiac arrest model was established in 16 rats in the 30-day hypobaric hypoxia group and in 22 rats in the 60-day hypobaric hypoxia group. There was no significant difference in the body weight of rats before modeling among the plain control group, 30-day hypobaric hypoxia group and 60-day hypobaric hypoxia group [g: 429.00 (389.25, 440.75), 440.00 (415.50, 486.25), 440.00 (400.00, 452.50), all P > 0.05]. The asphyxia induction time of rats in the 60-day hypobaric hypoxia group was significantly longer than that in the 30-day hypobaric hypoxia group (s: 294.59±75.39 vs. 234.31±93.86, P < 0.01), even about 1.4 times of the plain control group (s: 294.59±75.39 vs. 208.73±30.88, P < 0.01). There was no significant difference in the asphyxia induction time between the 30-day hypobaric hypoxia group and the plain control group (P > 0.05).

Conclusions: Rats treated in a hypobaric oxygen chamber for 60 days are more suitable for the preparation of high-altitude cardiac arrest model, and are also consistent with the oxygen reserve and hypoxia tolerance of high-altitude rats.