Position of Esophageal Balloon in Patients With Mechanical Ventilation

Transpulmonary pressure, which is the pressure at the airway opening minus pleural pressure, is frequently monitored in patients with mechanical ventilation. Because pleural pressure is difficult to measure in most clinical situations, esophageal pressure (Pes) is used as a surrogate. Catheter with air balloon is the most commonly used method to measure the Pes. Right position of the balloon is the key factor in accurate measurement of Pes, and the lower third part of esophagus is recommended as the target position of the balloon. The catheter is usually inserted into the stomach first, and then slowly withdrawn into the esophagus after inflation of the balloon. A negative pressure deflection replacing the positive pressure deflection during inspiration generally indicates the balloon's entering into the esophagus. This confirmation method depends on the normal function of diaphragm. However, it may not always be possible to obtain the standard pressure deflections in patients with mechanical ventilation, especially in those with diaphragmatic paralysis.

In present study, the investigators developed a simple method to confirm the balloon position by using a modified SmartcathG esophageal balloon catheter. The objective was to evaluate the validity of this method and to investigate the relationship between the cardiac artifacts of the Pes tracings and the position of the balloon.

Inclusion criteria

• adult patients receiving invasive mechanical ventilation

Exclusion criteria

• age under 18 years old
• esophageal varices
• evidence of active air leak from the lung, including bronchopleural fistula, pneumothorax, pneumomediastinum, or existing chest tube
• history of chronic obstructive pulmonary disease
• history of lung surgery
• pregnancy
• severe coagulopathy