Final answer:
The correct indication that a chest tube is functioning properly is the fluctuation of the fluid level within the water seal chamber. This fluctuation is related to the changes in intrathoracic pressure during respiration and suggests that the chest tube is maintaining the necessary negative pressure in the chest cavity.
Step-by-step explanation:
The nurse can discern that a chest tube is functioning properly if there is fluctuation of the fluid level within the water seal chamber. This fluctuation, also known as tidaling, occurs because of the changes in intrathoracic pressure during the respiratory cycle. When the patient inhales, the negative pressure in the chest cavity increases, causing the fluid level in the water seal chamber to rise. Conversely, when the patient exhales, the pressure decreases, and the fluid level falls. This indicates that there is no air leak and that the lung is re-expanded because the system is maintaining negative pressure, which is essential for lung expansion post-surgery.
The absence of fluid in the drainage tubing (option B) could mean that fluid is not draining as it should, which could be problematic. Continuous bubbling within the water seal chamber (option C) typically suggests the presence of an air leak, which is not normal functioning. Equal amounts of fluid drainage in each collection chamber (option D) is not relevant to the proper functioning of a chest tube connected to a suction and water seal drainage system.