Acute effects of mechanical ventilation with hyperoxia on the morphometry of the rat diaphragm

Background: Prolonged mechanical ventilatory support (MVS) combined with high oxygen concentrations has a negative impact on diaphragm function. However, the acute effects of MVS with hyperoxia have not been elucidated. Objective: To analyze the acute effects of mechanical ventilation with hyperoxia on the morphometry of the rat diaphragm. Methods: An experimental, prospective study was conducted with Wistar rats (weight: 400c20 g), which were randomly allocated to two groups. The control group (n=4) was anesthetized, tracheostomized and kept spontaneously breathing room air for 90 minutes. The experimental group (n=5) was also anesthetized, curarized, tracheostomized and kept in controlled mechanical ventilation for the same amount of time. Both groups were submitted to median thoracotomy for sample collection of costal fibers from the diaphragm muscle, which were sectioned every 5 km and stained with hematoxylin and eosin for the morphometric study. Independent Student's t tests were employed to investigate differences between groups, with a significance level of p