The effects of chest drainage on volume-controlled ventilation

Introduction: Chest drainage generates negative pressure, which might affect the transpulmonary pressure (TPP). We investigated whether chest drainage affects ventilating conditions during volume-controlled ventilation (VCV) using a thoracic and lung model, and what such an effect would be. Methods: VCV was started with a 250 ml of tidal volume (TV). Plateau pressures (Plat-Ps) were measured using no positive end-expiratory pressure (PEEP) and no chest drainage (baseline), followed by 10 and 20 cmH2 O PEEP/no drainage, 0, 10, and 20 cmH2 O PEEP/drainage with -10 cmH2 O, or 0, 10, and 20 cmH2 O PEEP/drainage with -20 cmH2 O. In addition, Plat-TPPs were calculated based on the measured Plat-Ps. End-expiratory TPPs (EE-TPPs), defined as the TPP at the end of expiration, were also calculated. Results: With no chest drainage, Plat-Ps increased with an increase in PEEP and increased when 20 cmH2 O of PEEP was applied. When -10 cmH2 O chest drainage was applied, the increase in Plat-Ps with 20 cmH2 O of PEEP was even larger. In cases where -20 cmH2 O chest drainage was applied, even with applying 10 cmH2 O of PEEP, Plat-Ps increased. Plat-Ps further increased with 20 cmH2 O of PEEP. When the same EE-TPPs were generated as a result of a combination of PEEP and chest drainage, Plat-TPPs were similar during VCV with the same TV. However, they were not identical. Conclusion: Negative intrapleural pressure by a chest tube drainage can mimic PEEP and affect respiratory mechanics in mechanically ventilated lungs. EE-TPPs through combinations of PEEP and chest tube drainage could induce overdistension of the lungs.