Figure 1.

Schematic representation of the respiratory system and relevant pressures. Note the single catheter equipped with an esophageal pressure balloon, gastric pressure balloon and an electrode array in between the two balloons. Orange lines represent the phrenic nerves. For calculations of the pressure gradients refer to the text. Pao, airway opening pressure; Paw, airway pressure; Pbs, pressure at body surface; Palv, alveolar pressure; Ppl, pleural pressure; Pes, esophageal pressure; Pga, gastric pressure.