How to Set Up a Chest Tube to Wall Suction

Setting up a chest tube to wall suction involves connecting the chest tube to a pleural drainage unit, filling the appropriate chambers, attaching the unit to a wall suction source, and dialing in the correct negative pressure. The standard target is −20 cm H₂O of suction, a level chosen because normal pressure inside the chest cavity hovers between 0 and −10 cm H₂O, so −20 gives enough pull to evacuate air or fluid without being excessive.¹ The process sounds straightforward, but the details matter: which type of drainage unit you’re using, how you confirm it’s actually working, and what to watch for once suction is running all determine whether the system does its job safely.

Understanding the Drainage Unit Before You Touch It

Modern chest drainage units are single-use, disposable plastic devices that combine what used to be three separate glass bottles into one compact box. Those three compartments each serve a distinct purpose. The collection chamber sits closest to the patient and catches fluid draining from the chest. The water seal chamber acts as a one-way valve, letting air bubble out of the pleural space but preventing room air from traveling back in. The suction control chamber regulates how much negative pressure is applied.² Every step of setting up suction depends on understanding which chamber you’re interacting with, because adding water to the wrong one or misreading the indicators will leave the system either ineffective or dangerously unpredictable.

Wet Suction vs. Dry Suction Units

The two main types of drainage units you’ll encounter differ in how they control suction. Knowing which one you have changes the setup process entirely.

A “wet” suction control unit uses a column of water to regulate negative pressure. You fill the suction control chamber to a specific level, usually marked at −20 cm H₂O. The height of that water column is what limits the suction, not the wall regulator. When suction is working correctly, you’ll see gentle, continuous bubbling in the suction control chamber. If the bubbling is vigorous or violent, the wall suction is set too high and needs to be turned down until the bubbling becomes calm. Over-bubbling doesn’t increase the suction applied to the patient because the water column caps it, but it does cause the water to evaporate faster, gradually lowering the actual suction level if nobody tops off the chamber.

A “dry” suction control unit replaces the water column with a spring-loaded mechanical regulator or similar device. You set the desired suction by turning a dial, typically to −20 cm H₂O, and then turn up the wall suction until an indicator on the unit confirms the system is active. There’s no bubbling in the suction control area to monitor, which makes the unit quieter and eliminates the evaporation problem. Dry suction units also tend to handle high airflow situations better. In bench testing of various drainage units, only dry-suction models maintained the set suction level when airflow exceeded 20 liters per minute, whereas many wet units became restrictive and allowed internal pressures to spike.³ For patients with large or bronchopleural air leaks, that distinction can be clinically significant.

One quirk worth knowing: all wet-design units showed reverse airflow in testing, which can mimic the appearance of an air leak when none actually exists.³ If you’re using a wet unit and see bubbling in the water seal chamber, it could be a genuine air leak from the patient’s lung or simply an artifact of the system design. This false positive is a well-documented headache that can delay tube removal.

Step-by-Step Setup

The exact steps vary slightly between manufacturers, but the general process for connecting a chest tube to wall suction follows a consistent sequence. Read the instructions packaged with your specific unit before starting, because chamber fill levels and indicator mechanisms differ.

Prepare the water seal chamber: Using sterile water, fill the water seal chamber to the line indicated on the unit, usually 2 cm. This chamber must be filled regardless of whether you’re using wet or dry suction control. It is the one-way valve that protects the patient. The phrase “placing a tube on water seal” actually refers to leaving this chamber active without adding wall suction, since modern units have the water seal built in as a permanent feature.⁴
Prepare the suction control (wet units only): Fill the suction control chamber with sterile water to the −20 cm H₂O mark, or whatever level is ordered. Skip this step for dry suction units.
Connect the drainage tubing: Attach the patient’s chest tube to the long tubing that leads into the collection chamber. Make sure all connections are snug and secured, often with tape or zip-tie-style connectors, depending on hospital protocol.
Position the unit: Place the drainage unit upright and below the level of the patient’s chest. Most units hook onto the bed frame or sit on the floor. If the unit tips or rises above the chest, fluid can flow backward toward the patient.
Connect to wall suction: Attach the suction tubing from the back of the drainage unit to the wall suction outlet. Turn the wall regulator up slowly.
Set and confirm suction: For wet units, increase wall suction until you see gentle, steady bubbling in the suction control chamber, then stop. For dry units, turn the regulator dial to −20 cm H₂O (or the ordered level), increase wall suction until the indicator confirms active suction, then stop adjusting.
Verify the water seal: Watch the water seal chamber. You should see the water level rise and fall with the patient’s breathing, a phenomenon called tidaling. This confirms the tube is patent and communicating with the pleural space. If there is an air leak, you’ll see bubbling here as well.

After everything is connected, mark the initial fluid level in the collection chamber with the time and date. This lets you and the next shift track drainage output accurately.

Why −20 cm H₂O Is the Default

The choice of −20 cm H₂O as a standard suction level is largely empirical rather than derived from a definitive clinical trial. The rationale is straightforward: the pleural space normally operates at pressures between 0 and −10 cm H₂O, so applying −20 cm H₂O of external suction ensures that any air entering the pleural space through a small leak gets evacuated faster than it accumulates.¹ For most routine situations, this level works well. Some surgeons order lower suction, such as −10 cm H₂O, after certain procedures or for specific patient populations, while others go higher when dealing with massive air leaks. The key point is that suction level should be set to the physician’s order, not assumed to be −20.

When Suction Helps and When Water Seal May Be Better

Not every chest tube needs active suction. After initial placement, a tube can run on suction to evacuate a large pneumothorax or hemothorax, and then be transitioned to water seal once the lung has re-expanded and drainage has slowed. Understanding when each mode is appropriate matters because the clinical outcomes differ.

In traumatic chest injuries, suction appears to offer measurable advantages. A meta-analysis comparing suction to water seal after tube thoracostomy for traumatic pneumothorax and hemothorax found that suction shortened chest tube duration by roughly three days and hospital stay by about four days, while also improving rates of full lung expansion nearly fivefold.⁵ An earlier systematic review found similar numbers, with suction also reducing persistent air leaks.⁶ So for trauma patients, the evidence leans toward keeping suction on.

After elective thoracic surgery, the picture is more nuanced. Research by Cerfolio and colleagues found that switching to water seal on postoperative day two actually helped resolve small air leaks faster than continued suction.⁴ The theory is that removing the constant pull of suction allows the pleural surfaces to come into contact and seal on their own. Large air leaks, however, did not benefit from this approach. So the clinical decision often hinges on leak size and the underlying condition, not a universal rule.

Tubing Management and the Stripping Debate

Once the system is running, keeping the tubing free of kinks and dependent loops is essential. A dependent loop, where a section of tubing hangs below the drainage unit and fills with fluid, creates a column of liquid that the patient must generate extra negative pressure to overcome. This can effectively reduce or negate the suction being applied. Route the tubing so it travels in a smooth, downhill path from the patient to the unit. Coil any excess tubing on the bed, not on the floor where it can get stepped on or kinked by wheels.

You may hear about “milking” or “stripping” the tubing to clear clots. Milking involves gently squeezing the tube between your fingers and sliding toward the drainage unit; stripping is a more aggressive version where you compress the tube against a firm surface and pull. Both practices have been used for decades in postoperative cardiac and thoracic care, but the evidence doesn’t support them. A study comparing stripped, milked, and untouched chest tubes found that stripping increased drainage volume in the early postoperative hours but that all tubes remained patent regardless of manipulation.⁷ More concerning, stripping can generate extremely low negative pressures inside the chest, with the potential to injure tissue.⁸ Given the risk of harm and the absence of proven benefit, routine stripping is generally discouraged. If you suspect a clot is blocking the tube, notify the clinical team rather than stripping on your own.

Watching for Complications During Suction

Several things can go wrong once suction is active, and recognizing them early prevents serious harm.

A sudden large rush of air or fluid immediately after connecting suction is expected and normal, especially with a new chest tube. That initial gush reflects the evacuation of accumulated air or fluid under positive pressure in the pleural space.¹ But if a lung that has been collapsed for a long time re-expands very quickly, the patient can develop re-expansion pulmonary edema, a condition where damaged blood vessels in the re-expanding lung leak fluid into the surrounding tissue. The exact mechanism is still debated, but it involves increased vascular permeability, reperfusion injury, and oxygen free radical damage to the blood vessel lining.⁹ This complication is uncommon but can be severe. To reduce the risk, some clinicians clamp the tube intermittently during the initial drainage of a large, long-standing pneumothorax, allowing gradual re-expansion rather than all at once.

Infection at the tube insertion site or within the pleural space is another concern. Chest tube-related empyema, including infections caused by resistant organisms such as MRSA, has been documented as a complication of tube thoracostomy.¹⁰ Keeping the insertion site clean, securing connections to prevent accidental disconnection, and monitoring for signs of infection such as fever, purulent drainage, or increasing white blood cell counts all form part of ongoing chest tube care.

Loss of suction is easy to miss if you’re not checking the unit regularly. In a wet suction unit, evaporation gradually lowers the water level in the suction control chamber, silently reducing the actual suction applied. Topping off the chamber periodically solves this. In any unit, a loose connection at the tubing, a cracked drainage unit, or a wall suction outlet that has been accidentally turned off will interrupt suction without triggering an alarm on most systems. Check the unit at the start of every shift and whenever the patient’s clinical status changes.

Pediatric Considerations

Children are not small adults when it comes to chest tube management, and the assumed benefits of suction don’t always translate. A study examining the effect of suction on chest tube progression in children with parapneumonic effusions found that once the effusion had drained, suction was actually associated with a delay in clinical improvement compared to water seal alone.¹¹ Suction didn’t help move children through the other stages of resolution any faster either. The likely explanation is that sustained negative pressure can prevent pleural surfaces from sealing and may irritate the pleural lining in a smaller chest. Pediatric teams often favor lower suction levels or earlier transition to water seal as a result.

Portable and Alternative Drainage Options

Wall suction ties a patient to the wall, which limits mobility and contributes to the deconditioning that slows recovery. Portable options exist for patients who are stable enough to move around.

The Heimlich valve is a small, one-way flutter valve less than 13 cm long that connects to the chest tube and empties into a flexible collection bag. It lets air and fluid drain out but prevents anything from flowing back in. The valve works in any position and never needs clamping. If the patient does need suction, a regulated suction source can be attached to the valve.¹² For patients with a resolving pneumothorax and no ongoing air leak, a Heimlich valve allows ambulation simply by carrying the drainage bag.

Compact portable drainage devices that incorporate a small collection chamber and a one-way valve have also been developed for outpatient chest tube management. In published case series, patients managed with these devices at home experienced no pneumothorax after removal, no empyema, and no pneumonia, and all reported tolerating the system well.¹³ These portable systems are increasingly popular in enhanced recovery pathways, where the goal is to get the patient up, walking, and discharged as soon as safely possible.

Autotransfusion Capability

In trauma settings where significant blood accumulates in the chest, some drainage units come equipped with an autotransfusion chamber or can be paired with a dedicated collection bag designed for re-infusing the patient’s own shed blood. Multiple commercially available autotransfusion systems exist, including models that provide a direct conduit for transfusion via a port connecting to dedicated transfusion giving sets. These closed systems reduce contamination risk compared to improvised approaches and don’t require expensive cell salvage devices.¹⁴ If autotransfusion is anticipated, the drainage unit with the autotransfusion feature needs to be set up from the start, because switching systems mid-drainage is messy and risks contaminating the collected blood. Check whether your facility stocks these units in the trauma bay or if they need to be ordered from central supply.

Common Mistakes That Undermine the Setup

Even when the system is assembled correctly, a few errors consistently trip people up. Filling the water seal chamber too high can create excessive resistance to air drainage. Forgetting to remove the cap from the suction port on the drainage unit before connecting wall suction means no suction reaches the patient, even though the wall gauge reads the correct level. Taping connections so aggressively that the tube can’t be disconnected in an emergency is also a problem; connections should be secure but not permanent.

Another frequent mistake is cranking the wall suction regulator to maximum in the belief that it delivers more suction to the patient. With a wet unit, the water column limits suction no matter what the wall reads; with a dry unit, the regulator dial on the device itself sets the cap. All that excess wall suction accomplishes is noise, evaporation, and the false sense that you’re being more aggressive. Follow the drainage unit’s instructions for how high to set the wall source, which usually means just high enough to activate the system’s indicators.

Finally, never clamp a chest tube while it’s connected to suction unless specifically instructed to do so for a particular clinical reason. A clamped tube with an ongoing air leak traps air in the pleural space, which can rapidly build into a tension pneumothorax. If you need to briefly disconnect the system for transport or troubleshooting, the safest default is to leave the tube unclamped and open to a water seal or Heimlich valve rather than clamped shut.

1
The Journal of Thoracic and Cardiovascular Surgery. Pleural mechanics and the pathophysiology of air leaks
2
PubMed. Chest Tube Drainage Devices
3
PubMed Central. Chest Drainage Therapy: What Comes out of Pandora’s Box Can Affect Patient Outcomes
4
JAMA Surgery. Comprehensive Review of Chest Tube Management: A Review
5
PubMed. Comparative effectiveness of suction versus water seal following tube thoracostomy in traumatic pneumothorax and hemothorax: An updated systematic review and meta-analysis
6
PubMed Central. Systematic review and meta-analysis of tube thoracostomy following traumatic chest injury; suction versus water seal
7
PubMed. Is milking and stripping chest tubes really necessary?
8
PubMed. Is manipulation of mediastinal chest drains useful or harmful after cardiac surgery?
9
PubMed Central. Severe re-expansion pulmonary edema after chest tube insertion for the treatment of spontaneous pneumothorax: a case report
10
PubMed Central. Chest tube-related empyema due to methicillin-resistant Staphylococcus aureus: could the chest tube be coated with antiseptics?
11
PubMed. The effect of suction on chest tube progression in children with parapneumonic effusions
12
PubMed Central. Heimlich valve and pneumothorax
13
The Annals of Thoracic Surgery. A new portable chest drainage device
14
Journal of Trauma and Injury. Autologous transfusion of hemothoraces in resuscitation after thoracic trauma: a narrative review