Abstract
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 cmH(2)O PEEP/no drainage, 10 cmH(2)O PEEP/drainage with - 10 cmH(2)O and 10 cmH(2)O PEEP/drainage with - 20 cmH(2)O. Finally, TV with 20 cmH(2)O and 30 cmH(2)O PEEP/no drainage was measured. Driving (inspiratory) pressure was maintained at 20 cmH(2)O during the whole experiment. RESULTS: TV was significantly increased by applying 10 cmH(2)O PEEP compared with baseline, further increased by applying - 10 cmH(2)O by drainage, similar to the value with PEEP 20 cmH(2)O with no drainage (end-tidal TPP of 20 cmH(2)O for both). TV decreased to < 50% of the baseline by applying 10 cmH(2)O PEEP with - 20 cmH(2)O by drainage, which was similar to that with 30 cmH(2)O PEEP with no drainage (end-tidal TPP of 30 cmH(2)O 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.