Fig. 1
From: Novel method of transpulmonary pressure measurement with an air-filled esophageal catheter
Air-filled catheter without balloon method. The esophageal catheter is placed at the lower-third of the esophagus, connected to an air-filled transducer bound to the monitor and pressurized by an air-filled perfusion bag. The three ways for controlling positioning are cardiac arteficts (blue arrows on Pes trace), esophageal-to-airway pressure change ratio (under passive—black arrows and active condition—white arrows) and X-rays projection of guidewire (extremity at the lower-third of the esophagus)