If a nurse notices that fluid in a chest tube has stopped fluctuating, what should be concluded?

When fluid in a chest tube stops fluctuating, this indicates that the pressure dynamics within the pleural space have changed significantly. In normal circumstances, the fluctuation of fluid levels in the chest tube reflects the changes in intrathoracic pressure, which is typically associated with breathing. If the lung has fully expanded, the negative pressure in the pleural space normalizes as there is no longer fluid or air in the pleural cavity that would cause continuing movement of the fluid in the chest tube. Therefore, the absence of fluctuation suggests that the lung has re-expanded and that normal respiratory mechanics are resuming.

In contrast, if the chest tube were occluded, there would likely be no drainage, and the fluid would remain static, indicating a different clinical concern. A lung collapse would be associated with continued fluctuation or a different collection of air or fluid that could create pressure changes in the system. Lastly, if the chest tube were properly positioned in the pleural space, fluctuations would still be expected as the lung engages in the normal mechanics of respiration. Thus, the cessation of fluid movement is most indicative of a fully expanded lung, demonstrating recovery from the previous pathology.