What is an expected finding in a patient with a tube thoracostomy connected to a chest drainage system?

In a patient with a tube thoracostomy connected to a chest drainage system, fluctuation in the water seal chamber is an expected finding indicating that the system is functioning correctly. This fluctuation, also known as "tidaling," occurs with changes in intrathoracic pressure, typically during inhalation and exhalation. When the patient breathes in, the pressure within the thoracic cavity decreases, causing the fluid level in the water seal chamber to rise. Conversely, upon exhalation, increased thoracic pressure causes the fluid level to fall.

This fluctuation is important as it confirms that the drainage system is properly allowing air and fluid to exit the pleural space while maintaining a seal against atmospheric pressure. An absence of fluctuations may indicate a problem, such as a kink in the tubing or re-expansion of the lung, while consistent drainage amounts may not adequately reflect the patient's condition or changes, especially in emergency situations. Continuous bubbling in the water seal chamber suggests a leak in the system, which requires immediate attention to prevent air from entering the pleural space. Therefore, fluctuation in the water seal chamber is a key indicator of proper chest tube function in a clinical setting.