The mortality and incidence of delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) rats were compared by intraperitoneal injection and inhalation.

180-230 g male wistar rats were randomly divided into intraperitoneal injection group(n=80), inhalation group (n=240) and control group 1 and control group 2 (n=8, respectively). According to 150 ml/kg, DEACMP animal models were made by intraperitoneal injection in 150 ml/kg dose of carbon monoxide in intraperitoneal injection group. According to different doses of CO, rats in inhalation group were divided into low dose group (1 000 ppm, n=80), middle dose group (3 000 ppm, n=80) and high dose group (4 000 ppm, n=80). Rats in blank control group were injected with equal volume of air (control group 1) or were put in the cabin filled with air (control group 2). The concentration of carboxy hemoglobin (HbCO) in the tail blood was monitored and the incidence of DEACMP was detected by water maze test.

The mortality of 3 000 ppm group, 4 000 ppm group and intraperitoneal injection group were 37.5% (30/80), 61.3% (49/80) and 40.0% (32/80), respectively. The mortality in 3 000 ppm group was lower than that in 4 000 ppm group, with statistical difference (χ²=9.03, P=0.003), but there was no significant difference between intraperitoneal group and 3 000 ppm group (χ²=0.11, P=0.746). The incidence of DEACMP in 3 000 ppm, 4 000 ppm and intraperitoneal injection group was 40.0% (20/50), 41.9% (13/31) and 14.6% (7/48), respectively. The incidence of DEACMP in 3 000 ppm group was higher than that in intraperitoneal injection group (χ²=7.93, P=0.005), but there was no significant difference between 4 000 ppm group and 3 000 ppm group (χ²=0.03, P=0.860).

3 000 ppm inhalation poisoning is the best way to build DEACMP animal model.