Potentially dangerous negative intrapleural pressures generated by ordinary pleural drainage systems

Clinical observation has identified cases in which the negative pressures exerted on patient chest drains have appeared to far exceed the level of suction intended. This study was designed to test whether the use of high rates of airflow in typical pleural/mediastinal drainage systems exerts excessively high negative pressures on the chest drainage tube.

Three pleural drainage systems were tested in vitro at negative pressure settings ranging, in 5-cm H(2)O increments, from 5 to 35 cm H(2)O. At each negative-pressure setting, each device was tested with three different rates of airflow. The negative pressures exerted in the chest drain were measured by water manometer and were compared with the initial pressure settings.

When a high rate of airflow was used, all three systems produced negative pressures that exceeded the pressure level initially set; two of the systems exerted negative pressures that were approximately double those intended, for all pressure settings.

Pleural drainage systems may exert excessive and potentially dangerous high negative pressures if high airflow is utilized. The risk to patients will be minimized if the airflow through the pressure-regulating chamber of the drainage system is adjusted to produce slow, consistent bubbling. High rates of bubbling and turbulence in the water column indicate that the negative pressure level may be excessively high, particularly for patients who do not have air leakage.