If the chest tube is not connected to suction and the patient is not on a ventilator, then the level of liquid in the limb of the water seal proximal to the patient should move higher on inspiration (due to negative pressure in the pleural space).
If the chest tube is not connected to suction and the patient is on a ventilator, then the level in tube should go down on inspiration (due to positive pressure in pleural space associated with mechanical ventilation).
If the chest tube is connected to suction, then:
(1) disconnect or turn off the suction
(2) let the level in the water-seal chamber equilibrate
(3) once equilibrated, observe the level of the fluid in the water seal for fluctuations.
If no fluctuations are seen during regular respirations, then the patient should be instructed to make a maximal inspiratory effort. If no fluctuation in the fluid level is seen, then the chest tube is probably not functioning.
If the fluid is observed to be draining fluid, then it should be left in place even if the level of fluid in the tube does not fluctuate.
If a tube is nonpatent, it is important to consider the probable cause and the location (within the pleural space vs outside the patient).
A chest tube may become nonpatent from:
(1) fibrin or other debris occluding the drainage holes
(2) blood clot within the tubing
Fibrin clot or debris occluding the drainage holes can be dislodged by injecting 50 mL of sterile saline into the tube. A risk of this technique is introduction of bacteria into the pleural space.
A blood clot can be dissolved by injecting streptokinase (250,000 IU) into the tube.
If a clot or debris can be seen obstructing the external portion of tubing, then this can be stripped by had or instrument out of the tubing.
If successful the level of fluid in the tubing should once again be observed to fluctuate with respiration.
