One of the scariest devices a therapist runs into in an ICU is the chest drain. It is connected through a long, large bore tube to a patient’s chest. The thought of carrying around a device filled with a patient’s blood unnerves some individuals.
It is not uncommon for a physician to write “patient may be on water seal for therapy.” If a therapist receives this order, they will need to be competent with moving their patient’s chest drain from wall suction to water seal and back again.
Wall Suction vs. Water Seal
A chest drain on “wall suction” means the patient’s chest drain is attached to the vacuum regulator (the device attached to the wall that controls the suction pressure). A chest drain on “water seal” means the chest drain is not attached to the vacuum regulator.
Bubbling in the Suction Control Chamber is Normal
People have been draining substances from the chest cavity for thousands of years,1 but it was not until after the Korean war when it became a standard practice in hospitals.2 In earlier days, chest drains did not have a suction control chamber/bottle and if an individual was to accidently increase the wall suction pressure, portions of lung tissue could evacuate through the chest tube.
Nowadays, the suction pressure is controlled by the water level in the suction control chamber (in “wet” suction models). Turning the vacuum regulator pressure to its maximum level will only increase the bubbling in the suction control chamber and will not negatively impact the lungs.
Empirically and in most nursing literature, it is common practice for nursing staff to turn up the vacuum regulator dial until continual, gentle bubbling occurs.3 Atrium, a maker of chest drainage systems, states that the vacuum regulator should be set at -80 mmHg pressure.4
If the suction pressure is set too high the water evaporates quicker from the drainage system and the nursing staff will have to refill it. If the suction pressure is too low, no bubbling will occur. The patient will have subtherapeutic suction pressure, which can possibly prevent the fluid or air from evacuating from the pleural cavity.
Bubbling in the Water Seal Chamber May Mean an Air Leak
Right next to the suction control chamber is the water seal chamber. The water seal chamber is the one-way valve that allows air to leave the pleural space, as with a pneumothorax. If removing excess air is the goal of the chest drain then the water seal chamber may bubble inconsistently, mainly on inspiration, as the air leaves the chest.
If the water seal is continuously bubbling, you should suspect an air leak. Think of the lungs as wrapped in plastic. An air leak occurs when there is a hole in the plastic wrap allowing air to escape from the lung tissue into to the pleural cavity. Holes can commonly be caused by trauma or surgery.
In summary, in “wet” suction drains, whether evacuating fluid or air, the only chamber that should be constantly bubbling is the suction control chamber when it is attached to the vacuum regulator.
- Munnell ER. Thoracic drainage. Ann Thorac Surg 1997;63(5):1497-502.
- Monaghan SF, Swan KG. Tube thoracostomy: The struggle to the “Standard of Care”. Ann Thorac Surg 2008;86(6):2019-22.
- CLINICAL DO'S & DON'TS: Managing a water-seal chest drainage unit. Nursing 2007. 2007;37(12):12