[Importance of pleural pressure for the evaluation of respiratory mechanics].
OBJECTIVE
Pleural pressure has to be known for the partitioning of respiratory system mechanical measurements into their lung and chest wall components. This review aimed at discussing alternative methods to obtain pleural pressure to calculate pulmonary mechanics, at reporting peculiarities of the esophageal balloon method for obtaining indirect pleural pressure, peculiarities of esophageal pressure measurement in sedated or anesthetized patients, at discussing direct pleural pressure and its correlation with esophageal pressure, in addition to reporting on the impact of PEEP on pleural and esophageal pressures.


BACKGROUND
Esophageal pressure variation reflects pleural pressure variation and may be used as alternative to direct pleural pressure in the study of lungs and chest wall mechanics. Esophageal pressure may be obtained with a delicate balloon placed inside the esophagus. Method and technique were observed and validated in humans and animals in different conditions and body positions. PEEP is a consolidated method for patients under mechanically controlled ventilation, however there are controversies about the close correlation between esophageal and pleural pressure in patients ventilated with PEEP, which may result in wrong respiratory mechanics calculation based on the esophageal pressure.


CONCLUSIONS
The esophageal balloon is the most common method to obtain indirect pleural pressure. In sedated or anesthetized patients without major respiratory compliance changes, esophageal pressure variation corresponds to pleural pressure variation when PEEP is applied.
Fernandes
Cláudia Regina
CR
Universidade de São Paulo, Brazil. crf@fortalnet.com.br