To investigate the establishment of intra-abdominal hypertension in rabbit model of liquid water sac, and the change rule of pressure-volume curve.

Experimental rabbits were taken as research object, five conventional water sacs (150 ml) and one pressurized water sacs were placed in the abdominal cavity. Animal model of intra-abdominal hypertension was established with injection of 0.9% sodium chloride solution (NS) into pressurized water sac. Intra-abdominal pressure (IAP) was measured and recorded after each injection of 50 ml solution. The relationship between the increase volume of intra-peritoneal solution and abdominal pressure was analyzed by drawing pressure volume curve and simple linear regression method.

After tension-free abdominal surgery, the total volume of peritoneal NS solution was 750 ml, and the initial abdominal pressure was 0 cmH₂O. With the injection of NS solution, abdominal pressure increased slowly until the total volume reached 900 ml, and abdominal pressure was 8 cmH₂O (5.88 mmHg, 0.784 kPa). Then abdominal pressure was increased significantly followed by15 cmH₂O (11.03 mmHg, 1.47 kPa) at 950 ml, 28 cmH₂O (20.59 mmHg, 2.744 kPa) at 1 000 ml and55 cmH₂O (40.44 mmHg, 5.39 kPa) at 1 050 ml. There was a functional relationship between abdominal pressure and peritoneal volume: Y=0.164 2X-132 (r=0.896, t=4.504, P=0.006).

The liquid animal model of intra-abdominal hypertension can be successfully established by the improved superposition of water sac. The pressure-volume curve is a unidirectional curve, gradually increasing with the addition of intra-peritoneal solution. After exceeding the compensatory critical point, a small amount of intra-abdominal fluid can cause significant increase in abdominal pressure with a trend of sustained growth.