The transdiaphragmatic pressure (Pdi; calculated as the difference between the gastric and esophageal pressures), ranged from 10.87 to 14.95 cm H
2O during spontaneous inspirations. The Pdi represents the gastroesophageal pressure gradient, and it can be considered a driving force for the gastric content to reflux into the esophagus [
4]. There is a strong linear correlation between the lower esophageal sphincter (LES) pressure and Pdi. Inspirations made with a closed mouth and nose or a closed glottis (effort levels of 75 to100 %) can cause an increase in the LES pressure of between 127.8 and 179.5 cmH
2O [
4]. NIV may have some problems related to air pressure and flow, such as gastric insufflation (30 to 40%) and aspiration (5%) [
5]. Murphy and colleagues [
1] did not report on the side effects of the high pressure strategy.