Respiratory Muscle Contraction Characteristics and Potential Mechanisms in Severely Burned Rats.

Post-burn hypermetabolism remains an important clinical problem. During this phase, there is a significant loss of diaphragmatic proteins. Better understanding of respiratory muscle dynamics and potential mechanisms affecting respiratory muscle function is necessary for the development of effective therapeutic approaches. Male wistar rats were subjected to 50% total body surface area (TBSA) burns and sham injuries, and respiratory muscle function was assessed with 0, 1, 4, 7, and 14 d post-injury, including Pulmonary function, blood gas analysis, transdiaphragmatic pressure, diaphragm ultrasonography, isolated diaphragm contractility, and fatigue index. protein oxidative stress content, and ATP levels. Burned Rats had significantly reduced inspiratory time, expiratory time and tidal volume, and significantly increased respiratory rate and minute ventilation. At the same time, the isolated diaphragm contractility, specific force during fatigue, and fatigue index were significantly decreased in the burned rats. Pdi, Pdimax, diaphragm thickness, diaphragm thickening fraction, and diaphragm excursion also decreased significantly post-burn, whereas the Pdi/Pdimax ratio increased significantly. Finally, the content of protein carbonyls and lactic acid of burned rats were increased, and ATP levels of burned rats was decreased. The present study demonstrates the dynamic changes in diaphragm contractile properties post-burn from both in vivo and in vitro perspectives, while cursorily exploring the possibility that protein oxidative stress and reduced ATP production may be the cause of diaphragm dysfunction. This understanding contributes to the development of methods to mitigate the extent of diaphragmatic function loss after severe burns.