Features of Histological Changes in the Diaphragm 14 Days After the Use of Low-Pressure Pneumoperitoneum

Abstract

The establishment of an optimal level of intra-abdominal pressure during laparoscopic surgery represents a considerable challenge for surgeons, with the most commonly used range being 12 to 15 mmHg, which allows for a sufficient working space. The aim of this work was to study the morphological features of the lumbar, costal and tendon parts of the diaphragm under low-pressure pneumoperitoneum modelling and long-term structure recovery. The experiment was performed on sexually mature rats of the reproductive period (6-7 months), weighing (230.0±20.0) grams, in the amount of 30 animals. The animals were divided into two experimental groups. The difference in the groups was in the timing of diaphragm sampling. In the first group, the diaphragm was sampled immediately after five hours of pneumoperitoneum, and in the second group 14 days after the simulated pneumoperitoneum. Histological examination of the microsections after five hours revealed destructive changes in all structural components of the diaphragm. Muscle fibres exhibited a compact arrangement, frequently with blurred boundaries, and a loss of differentiation from the stroma. Myofibrils undergo a transformation, becoming undulated, whilst transverse striations are fragmented or absent. The stroma exhibits thickening perivascularly, with adipose tissue representing this structure. The veins and capillaries are full of blood, and there is a distributed leukocytosis. In the arterioles, there is evidence of wall oedema, endothelial desquamation and moderate blood filling. The tendon part loses its compactness. The collagen fibres of the tendons were severely disintegrated, disintegrated and underwent lysis, and there was often detection of haemorrhages and reactive inflammation. After 14 days, the muscle fibres of the diaphragm exhibited an equidirectional, parallel and compact arrangement, and their thickness varied slightly. The nuclei were oval-round in shape, with a characteristic sublemmal arrangement. The endomysium was found to be thin, and was composed of a limited number of collagen fibres, among which hemocapillaries, filled with blood to a moderate degree, were visualised. The perimysium is more pronounced, especially around veins and arterioles, and a greater proportion of collagen fibres in the tendons are parallel to each other and retain their integrity. Low-pressure pneumoperitoneum for 5 hours leads to structural changes in the diaphragm. These changes are reversible, as demonstrated by the complete recovery of all diaphragm parts 14 days after the application of 5 mmHg pneumoperitoneum.