Objective: 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.
pleural drainage systems were tested in vitro at
negative pressure settings ranging, in 5-cm H2O increments,
from 5 to 35 cm H2O. 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.
Results: 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
Conclusions: 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.