A phase 3 controlled clinical trial on intrapulmonary pressures during laparoscopic cholecystectomy was conducted at the Manuel Ascunce Domenech University Hospital, from September 2016 to February 2020. The universe consisted of patients who met the inclusion criteria and a sample of 106 patients who were divided into two groups of 53 patients each, by simple random method. The primary source of data collection was the medical records and the results of a survey. The data were collected in a model designed according to the bibliography. Results: There was an increase in peak inspiratory pressure and plateau pressure after pneumoperitoneum with a decrease in both after inversion of the I:E index, as well as arterial hypertension, arrhythmias and arterial hypotension, unrelated to the application of the inverted I:E index. Conclusions: The inversion of inspiration expiration contributed to improve the effects of pneumoperitoneum on intrapulmonary pressures while maintaining adequate oxygenation and null cardiovascular effects.