The effects of chest drainage on pressure-controlled ventilation.

Background: The use of pressure-controlled ventilation (PCV) for anesthesia management is becoming more commonly used. Chest drainage is commonly performed after thoracic surgery, and the negative pressure it generates might affect the transpulmonary pressure (TPP). In the present study, we investigated how chest drainage could affect ventilating conditions during PCV.

Methods: We created a hand-made simple thoracic and lung model, which was connected to an anesthesia machine. The tidal volume (TV) was measured with positive end-expiratory pressure (PEEP) 0 and no chest drainage (baseline), followed by 10 cmHO PEEP/no drainage, 10 cmHO PEEP/drainage with - 10 cmHO and 10 cmHO PEEP/drainage with - 20 cmHO. Finally, TV with 20 cmHO and 30 cmHO PEEP/no drainage was measured. Driving (inspiratory) pressure was maintained at 20 cmHO during the whole experiment.

Results: TV was significantly increased by applying 10 cmHO PEEP compared with baseline, further increased by applying - 10 cmHO by drainage, similar to the value with PEEP 20 cmHO with no drainage (end-tidal TPP of 20 cmHO for both). TV decreased to < 50% of the baseline by applying 10 cmHO PEEP with - 20 cmHO by drainage, which was similar to that with 30 cmHO PEEP with no drainage (end-tidal TPP of 30 cmHO for both).

Conclusions: TV was maintained at similar levels with the same TPP, regardless of PEEP or negative pressure by chest drainage change, suggesting that negative intrapleural pressure by the chest tube drainage system might mimic PEEP from the point of TV.