Aim:
To investigate the morphological changes in the costal part of the diaphragm following the induction of pneumoperitoneum at 10 mmHg for varying durations in a rat model, using objective methods.

Material and methods:
To create the model of the experiment, 50 rats aged 5-6 months and weighing (225.0±20.0) grams were used. The control group underwent a puncture of the abdominal wall with a Veress needle, which was maintained for a period of five hours. This was done to ascertain whether such an intervention would result in histological changes to the diaphragm. In the main groups, carboxyperitoneum was created at a pressure of 10 mmHg.

Results:
The microscopic appearance of this type of muscle was observed in the preparations obtained from the intact group of animals. The sarcoplasmic sections obtained after the created pneumoperitoneum showed destruction of the basal membranes of muscle fibres in most cases. However, in some instances, muscle fibres with preserved sarcolemma were also observed, although damage was evident through the disintegration of sarcoplasm into fragments, partial lysis, vacuolisation and eosinophilic degeneration. Some myofibres became uncoiled and deformed. The stroma increased in oedema, the volume of adipose tissue and the number of collagen fibres, mainly around the vessels, and haemorrhagic infiltration was also noted. The intensity of these changes was found to depend on the duration of pneumoperitoneum.

Conclusions:
The creation of pneumoperitoneum by carbon dioxide results in morphological and structural alterations to the costal part of the diaphragm. The extent of these changes is directly proportional to the duration of intra-abdominal pressure.