[A comparative study of "constant volume" animal model and "constant pressure" animal model of intra-abdominal hypertension].

OBJECTIVE: To select the animal model more consistent with the pathophysiology of abdominal compartment syndrome (ACS) through the comparative study of the methods of multiple water sacs superimposed compression and gas perfusion.

METHODS: Ten experimental pigs were randomly divided into two groups (n = 5): the "constant volume model" (constant volume model group) and the "constant pressure model" (constant pressure model group) of intra-abdominal hypertension. The models were prepared by the method of water sac superposition and pressurization, and artificial pneumoperitoneum respectively. The abdominal pressures of both groups were 25 mmHg (1 mmHg = 0.133 kPa) and observed for 4 hours. The pressure was measured once an hour for 4 hours and the pressure-time curves of the two groups were drawn respectively. The experimental animals were sacrificed 4 hours after modeling. The heart and lung were harvested, and the histopathological changes were observed by hematoxylin-eosin (HE) staining.

RESULTS: Two groups of experimental pigs were successfully modeled. The abdominal pressure gradually increased at 0, 1, 2, 3, 4 hours after operation in the constant volume model group (mmHg: 25.0±0, 27.1±0.2, 29.4±0.1, 30.9±0.2, 33.1±0.1), and there was a positive correlation between the abdominal pressure and time (functional equation: Y1 = 25.102 0+1.996 0X1 ; R2 = 0.996 2, P = 0.000 1). The abdominal pressure value in the constant pressure model group at 0, 1, 2, 3, 4 hours were maintained 25 mmHg, and there was no linear correlation between the abdominal pressure and time (functional equation: Y2 = 25). HE staining showed that in the constant volume model group, the myocardial fibers were accompanied with hyaline degeneration, significantly reduced transverse lines, part of myocardial fiber atrophy, and visible nuclear aggregation; hemorrhage, chronic inflammatory cell infiltration and inflammatory exudation were found in the lung tissues. In the constant pressure model group, partial atrophy of myocardial fiber, partial hypertrophy, focal hyaline degeneration, disappearance of local striae, hyaline degeneration of myocardial fiber, dilation and congestion of intermyocardial artery were observed. Slight hyperplasia of alveolar epithelium in some areas, heart failure cells, dilation and congestion of bronchi and trachea artery, a large number of red blood cells and uniform light staining substances in lumen were found.

CONCLUSIONS: After the model was made by the method of multiple water sacs, the pressure of the abdominal cavity continued to increase with the development of the disease, which was in line with the clinical pathological changes of ACS, and was more suitable for making the animal model of the intra-abdominal hypertension.