Assessing Bubbling in the Water Seal

Q. I have been asked to do a chest tube competency for our surgical unit staff and have not had any experience myself. After viewing the video about managing chest drainage and asking others here questions I am still a little confused about the water seal chamber. Bubbling in the chamber can be both good and bad, one indicates an air leak, the other indicates a normal condition. I’m just not sure how to distinguish between good and bad exactly. Also someone here told me that when the water level rises in the water seal chamber that also can be good and bad. Again could you explain this? I am also confused about tidaling as it says you should see this but it can be normal not to occur. Everything about this chamber seems to be a contradiction. How do I know what is good vs bad?

Robert Cole, RN
Nursing Education Department
St Joseph Health Services of RI

A. Rather than thinking about good vs. bad, it might be easier to think about whether bubbling is expected or unexpected. Bubbling occurs in the water seal chamber when air is entering the chest drain. When you first apply suction, there should be a little bubbling in the water seal as air is pulled through from the collection chamber. If no other air enters the system, the bubbling should soon stop. Bubbling continues when air is entering the system.

  • What is going on with your patient? If the tube has not been in for long and the patient had a pneumothorax or lung resection surgery, you should expect bubbling.
  • What have previous nursing assessments shown? If the patient is 18 hours post-op and has had bubbling in the water seal since leaving the OR, I wouldn’t be worried at all. However, if the patient is 36 hours post op and I am seeing bubbling after 24 hours of no bubbling, I’d want to investigate further.

If an air leak is not expected from your patient assessment, there may be a leak in the system – somewhere between the chest tube and the drain itself. An air leak can be “normal” when it is expected and makes sense with the rest of the patient assessment. On the other hand, if you expect bubbling and don’t see it and the patient is short of breath with significantly diminished breath sounds on the side with the chest tube, the tube could be blocked and again, require additional assessment.

Here’s an analogy: let’s say a 32 year old man comes in to the ER with a broken wrist after slipping on an icy sidewalk. You put him on a monitor for sedation for a closed reduction, and you notice he’s in bigeminy. That becomes an incidental finding that doesn’t need treatment. If, however, you see the same rhythm in a patient having an MI with unstable blood pressure, it would need more investigation and probably speedy treatment.

As for the fluid in the water seal chamber, the water seal is a manometer that can measure intrapleural pressures. Pressure changes in the pleural space that occur with breathing will be seen as fluctuations in the level of the water within the tube. These fluctuations, called “tidalling,” may be as great as 5 to 10 cmH2O with normal spontaneous breathing. The water level will go up (more negative) during inspiration, and go down (return to baseline) during exhalation. If the patient is receiving positive pressure ventilation, the water level will go down (more positive) during inspiration, and go back up (return to baseline) during exhalation, reflecting the higher positive pressure in the chest with mechanical ventilation. If there is no tidalling, it could mean that:

  •  The tubing is kinked
  • The tubing is clamped
  • The patient is lying on the tubing
  • There is a dependent, fluid-filled loop in the tubing
  • Lung tissue or adhesions are blocking the catheter eyelets
  • No air is leaking into the pleural space and the lung has re-expanded

Once again, your complete patient assessment and knowledge of what’s been going on over the past 24 to 48 hours will help you interpret these findings.