Suction: Wet or Dry?

Suction: Wet or Dry?

Q. Is there any research to show that the water (wet) suction is more reliable than your dry suction? What are the advantages/disadvantages of each?

A. I’m happy to discuss wet and dry suction in general. For individual product specifications, I’ll have to refer you to the manufacturer of the chest drain(s) you use. I am not aware of any published research comparing the two approaches. Both will protect the patient and provide a window to the pleural space through the water seal chamber for asses

Chest drain with wet suction control



A water column is the original method used to control the amount of negative pressure that can be transmitted to the chest. When disposable integrated drains were developed, this was transformed into a suction control chamber. The level of the

water in this chamber determines the limit of the negative pressure that can be transmitted to the chest. Challenges with water-based systems are the noise of the bubbling, and the potential for water evaporation. As water evaporates and the water level drops, the amount of negative pressure transmitted to the chest will also decrease. In addition, water-filled units take longer to set up, they weigh more when operating (a potential issue for transport), and if the drain is knocked over, the water can spill over into other chambers.

There are basically two types of dry suction. A small minority of drains operate with a restrictive orifice mechanism. In these drains, you would adjust a small knob that makes the path by which air leaves the drain larger or smaller in diameter, which indirectly limits the negative pressure. The problem with this is that it severely limits air flow out of the drain. A patient with a pneumothorax may have retained air as a result, particularly if on a ventilator. In addition, there is no self-adjustment if there is a change in the amount of flow from the vacuum source or from the patient.

The other, much more common, type is a self-regulating dry suction in which a small regulator is built into the drain. As long as there is adequate flow from the wall (which will be indicated on the drain) it will accurately adjust to changes in the source vacuum or the patient to maintain suction at the level set on the drain. It’s also silent. No bubbling is needed. In addition, these drains provide a wider range of suction levels, from -10cmH2O to -40cmH2O; there’s no evaporation to worry about; if the drain is knocked over, there is much less water to move between chambers; it’s lighter during operation; and it’s quicker to set-up. However, all these conveniences come with a higher price per drain.