Potentially dangerous negative intrapleural pressures generated by ordinary pleural drainage systems

Objective: Clinical observation has identified cases in which the negative pressures exerted on patient chest drains have appeared to far exceed the l evel of suction intended. This study was designed to test whether the use o f high rates of airflow in typical pleural/mediastinal drainage systems exe rts excessively high negative pressures on the chest drainage tube. Methods: Three pleural drainage systems were tested in vitro at negative pr essure settings ranging, in 5-cm H2O increments, from 5 to 35 cm H2O. At ea ch negative-pressure setting, each device was tested with three different r ates of airflow. The negative pressures exerted in the chest drain were mea sured by water manometer and were compared with the initial pressure settin gs. Results: When a high rate of airflow was used, all three systems produced n egative pressures that exceeded the pressure level initially set; two of th e systems exerted negative pressures that were approximately double those i ntended, for all pressure settings. Conclusions: Pleural drainage systems may exert excessive and potentially d angerous high negative pressures if high airflow is utilized. The risk to p atients will be minimized if the airflow through the pressure-regulating ch amber of the drainage system is adjusted to produce slow, consistent bubbli ng. High rates of bubbling and turbulence in the water column indicate that the negative pressure level may be escessively high, particularly for pati ents who do not have air leakage.