How to Properly Place a Chest Tube to Water Seal

Placing a chest tube to water seal involves inserting a drainage tube into the pleural space and connecting it to a sealed collection system that uses a column of water to act as a one-way valve, allowing air and fluid to escape the chest without letting anything back in. The procedure has been a cornerstone of managing pneumothorax, hemothorax, and pleural effusions for over a century, yet complications from improper technique remain a real and well-documented source of harm. Getting each step right, from site selection through final connection to the drainage unit, is what separates a smooth recovery from a prolonged hospital stay.

Choosing the Right Site

The standard insertion site for most chest tubes is the so-called “triangle of safety.” This is a zone on the lateral chest wall bounded by the base of the armpit above, the outer edge of the pectoralis major muscle in front, the outer edge of the latissimus dorsi muscle behind, and the nipple line (roughly the fifth intercostal space) below.¹ Inserting within this triangle keeps you away from the internal mammary artery, the heart, and the major vessels at the lung root. It also avoids the diaphragm and abdominal organs sitting just below.

In practice, most clinicians target the fourth or fifth intercostal space in the mid-axillary line. You identify the correct rib space by palpating down from the clavicle or up from the costal margin and confirming your position against the nipple line. The incision goes just above the rib below the target space, because the intercostal nerve, artery, and vein run along the inferior border of each rib. Cutting too close to the lower rib risks vascular injury and significant bleeding.

Landmark-based insertion works well in most patients, but body habitus can make surface anatomy unreliable. An elevated hemidiaphragm, morbid obesity, or large pleural effusion can shift where structures actually sit. Ultrasound guidance has gained traction for exactly this reason. In one retrospective series of ultrasound-guided small-bore drain placements, every tube was successfully positioned using real-time imaging, and there were no injuries to abdominal organs, intercostal arteries, or lung parenchyma.² Ultrasound lets you confirm the presence of fluid or air, identify the diaphragm, and watch the needle or drain enter the pleural space in real time.

Preparing the Patient

The patient is typically positioned semi-recumbent with the arm on the affected side raised above the head or resting on the opposite shoulder. This opens up the intercostal spaces and pulls the scapula forward and out of the way. If the patient cannot sit up, a lateral decubitus position with the affected side up also works.

After sterile preparation and draping of the insertion site, local anesthesia is essential. Lidocaine is infiltrated in layers: first into the skin and subcutaneous tissue, then down through the intercostal muscles, and finally into the parietal pleura itself. The pleura is the most pain-sensitive layer, and inadequate anesthesia here is the main reason patients report severe discomfort during the procedure. Many practitioners aspirate with the syringe as they advance, and the return of air or fluid confirms they have reached the pleural space and are at the right depth. Procedural sedation with a short-acting benzodiazepine or opioid is commonly added for patient comfort, depending on the clinical setting.

Making the Incision and Entering the Pleural Space

The skin incision is made horizontally, about two to three centimeters long, typically one rib space below the intended entry point into the chest. This offset creates a subcutaneous tunnel so that when the tube is eventually removed, skin and muscle layers do not line up, reducing the risk of air sucking back in through the wound.

From here, the blunt dissection technique is the accepted standard. Using a curved clamp (a Kelly or similar instrument), you spread through the subcutaneous tissue and intercostal muscles, pushing fibers apart rather than cutting them. When the clamp pops through the parietal pleura, you typically get a rush of air or fluid. The critical next step is to sweep a gloved finger into the pleural space. This finger exploration confirms that you are truly inside the chest, that no adhesions tether the lung to the chest wall at that spot, and that no organs (particularly the diaphragm, liver, or spleen) are in the path of the tube.³

The trocar technique, where a sharp-tipped stylet inside the tube is used to puncture directly through the chest wall, has fallen out of favor. A comparative review found that the trocar method is associated with a higher incidence of tube malposition and complications compared with blunt dissection.⁴ Without digital exploration, there is no way to verify the path before committing the tube. Case reports have documented retained surgical blades and organ injuries from sharp insertion techniques, reinforcing why guidelines recommend blunt dissection and finger sweeps before any tube goes in.⁵

Directing and Inserting the Tube

Once the pleural space is confirmed, the chest tube is guided in along the finger or the clamp. For a pneumothorax, the tube is directed anteriorly and superiorly, because free air rises to the apex of the chest when the patient is upright. For a hemothorax or effusion, the tube is aimed posteriorly and toward the base, where fluid pools by gravity. In trauma, the tube is generally directed posteriorly and superiorly to handle both air and blood.³

You advance the tube until all the side holes (the fenestrated portion) are inside the chest. Leaving a side hole in the chest wall or subcutaneous tissue can cause subcutaneous emphysema or allow air to leak into the tissue planes. A visual check that the last hole has cleared the chest wall and fogging of the tube with respiration are practical confirmation signs. Most tubes have a radiopaque stripe or depth markings to help verify position. A chest X-ray after placement confirms the tube’s location, whether the lung has re-expanded, and whether fluid has been adequately drained.

Securing the Tube

An insecure chest tube that partially backs out is a genuine danger, so fixation matters more than many operators appreciate. A scoping review of fixation methods identified at least nine different principles used to keep drains in place, including sutures through or around the tube, adhesive dressings, cable ties, external coils, and subcutaneous tunneling. No single technique has proven definitively superior, but evidence trends suggest that combining sutures with a secondary method like a dressing or cable tie offers the most reliable hold.⁶

The most common approach in practice is a horizontal mattress “stay suture” placed through the skin edges on either side of the incision, left long so it can be tied to close the wound when the tube comes out, plus a separate anchoring suture or silk tie wrapped securely around the tube itself. An occlusive dressing (often a combination of petroleum gauze and adhesive tape or a transparent film) covers the site. The dressing seals the insertion point from air entry and should be checked regularly for moisture or loosening.

Connecting to the Water Seal Drainage System

The water seal is the heart of the drainage apparatus. In a traditional three-chamber system, the first chamber collects fluid, the second is the water seal chamber, and the third controls suction. The water seal chamber contains a column of sterile water (usually about two centimeters deep). When the patient exhales or coughs, positive pressure in the pleural space pushes air through the water column, and you see bubbles. On inspiration, the slight negative pressure in the pleural space tries to draw air back, but the water column blocks it. This is the one-way valve principle that prevents outside air from re-entering the chest.

When you connect the chest tube to the drainage unit, make sure all connections are tight and secure. Loose connections are one of the most common causes of a malfunctioning system. The tubing should run from the patient to the collection device without dependent loops, because fluid pooling in a loop acts as an additional water seal that increases the resistance to drainage and can impede air escape. Keep the collection device below the level of the patient’s chest so gravity assists drainage and fluid cannot flow back into the pleural space.

Once connected, you assess for three things: tidaling, bubbling, and drainage. Tidaling means the water level in the seal chamber fluctuates with breathing, rising on inspiration and falling on expiration (reversed if the patient is on a ventilator). This confirms the tube is patent and communicating with the pleural space. Continuous bubbling in the water seal chamber indicates an ongoing air leak, either from the lung itself or from a leak in the system. Intermittent bubbling with cough or expiration is expected when air is still escaping. Fluid drainage is measured and recorded hourly in the acute phase.

Water Seal Versus Suction

One of the most common management decisions after a chest tube is in place is whether to apply wall suction or simply leave the system on water seal (gravity drainage only). The evidence here is reassuringly undramatic: for many patients, there is no meaningful difference.

A systematic review and meta-analysis of trials comparing suction to water seal after lung resection found no significant difference in the duration of air leak, time to chest tube removal, or length of hospital stay.⁷ Water seal was, however, associated with a higher incidence of postoperative pneumothorax, which makes sense: suction actively pulls the lung toward the chest wall, while water seal relies on the lung’s own tendency to re-expand. In a trial of patients after open heart surgery, switching from wall suction to water seal did not increase complications, drainage volume, or time the tube stayed in.⁸

In practice, suction (typically set at −20 cm H₂O) is often applied initially, especially in the immediate postoperative period or when there is a large air leak or significant lung collapse. Once the air leak has diminished and the lung looks well expanded on imaging, many protocols transition to water seal as a trial before removal. If the lung stays up and no new air leak appears, the tube can come out. If the lung drops, suction goes back on. This stepwise approach is the standard at most thoracic surgery centers.

Selecting Tube Size

Chest tubes range from small-bore catheters (roughly 8 to 14 French) to large-bore surgical tubes (28 to 36 French). The traditional teaching was that large effusions and hemothoraces demand large-bore tubes to prevent clotting and blockage, while small pneumothoraces can get by with a pigtail catheter. That dogma has softened considerably.

A multicenter randomized trial comparing small 14-French percutaneous catheters to large 28- to 32-French chest tubes for traumatic hemothorax found the small catheters were equally effective at draining blood, with no difference in complications. Patients reported better comfort scores with the smaller tubes.⁹ A meta-analysis of four randomized trials totaling 676 trauma patients reinforced this, showing no significant difference in failure rates or complication rates between small and large tubes. Duration of tube placement was actually shorter with the smaller ones.¹⁰ That said, the meta-analysis noted that cumulative evidence remains underpowered, so the last word is not yet written.

In non-trauma settings, a comparison of small-bore intercostal catheters and large-bore tubes for various pleural diseases showed comparable success rates. The dwell time was shorter and pain was dramatically lower with small-bore catheters: the mean duration of analgesia was about two days for the small tubes versus eight days for the large ones.¹¹ The practical takeaway is that smaller tubes are adequate for most indications and much better tolerated, but for massive hemothorax with active bleeding, many trauma surgeons still prefer a large-bore tube to minimize clotting risk.

Complications and How to Avoid Them

Despite being one of the most commonly performed procedures, chest tube insertion carries a long list of potential complications. The most serious include injury to abdominal organs (liver, spleen, or diaphragm), damage to intercostal or pulmonary vessels, and fistula formation.¹² More commonly, clinicians encounter tube malposition, blocked drains, subcutaneous emphysema, insertion-site infections, and tubes that dislodge.¹³

Most of these are preventable with careful technique. The key safeguards include:

Strict sterile technique: full draping, gown, gloves, and skin antisepsis reduce insertion-site infections.
Blunt dissection only: avoiding trocars and sharp insertion reduces organ injury and malposition.
Finger exploration: sweeping the pleural space with a finger before advancing the tube catches adhesions and confirms you are in the right compartment.
Post-insertion imaging: a chest X-ray after placement catches malpositioned tubes before they cause problems.
Secure fixation: sutures combined with an occlusive dressing prevent the tube from backing out.

Re-Expansion Pulmonary Edema

One complication that deserves its own discussion is re-expansion pulmonary edema. When a lung that has been collapsed for a prolonged period is suddenly re-inflated, fluid can flood the alveoli on the affected side, producing acute respiratory distress. The pathophysiology involves several overlapping mechanisms: reperfusion injury from sudden blood flow to previously collapsed tissue, increased capillary permeability from an inflammatory cascade, and mechanical damage to delicate alveolar capillaries from the abrupt pressure change.¹⁴

The risk goes up with the duration and severity of lung collapse. In one study of spontaneous pneumothorax patients, those who developed re-expansion edema had an average collapse duration of nearly eight days, compared to about two and a half days in those who did not.¹⁵ The degree of collapse also mattered independently. The practical implication is that when you are draining a large, long-standing pneumothorax or effusion, controlled re-expansion is wise. Some clinicians clamp the tube intermittently or limit initial drainage volumes (often cited as no more than about 1 to 1.5 liters of fluid in the first hour for large effusions) to let the lung re-expand gradually.

When and How to Remove the Tube

The criteria for removal are straightforward in principle: the lung is fully expanded on imaging, drainage has dropped below a threshold (commonly 200 mL per day or less, though this varies by institution), and there is no ongoing air leak, meaning the water seal chamber has stopped bubbling. Many protocols include a period on water seal without suction as a final test before pulling the tube.

The mechanics of removal are less settled than you might expect. The traditional teaching split into two camps: remove the tube at end-inspiration (when the lung is fully inflated against the chest wall, theoretically sealing the hole) or at end-expiration (when intrapleural pressure is least negative, reducing the chance of air being sucked in). A randomized trial of over 340 patients found that removal during full expiration resulted in new or larger pneumothorax in about 19% of cases, compared to about 32% with removal during full inspiration.¹⁶ However, a later meta-analysis pooling more data concluded that there was no appreciable difference between the two timing strategies.¹⁷ In practice, the most important things are to remove the tube in one swift motion, immediately cover the site with an occlusive dressing (petroleum gauze works well), and tie the pre-placed stay suture to close the wound. A follow-up chest X-ray a few hours later confirms the lung has stayed up.

Digital Drainage Systems

Traditional water seal systems work, but they have limitations. Assessing an air leak by watching bubbles is subjective, and different clinicians can disagree about whether bubbling has truly stopped. Digital drainage systems replace the analog water column with electronic sensors that measure airflow and pleural pressure in real time, displaying the data on a screen and logging it continuously.¹⁸

Currently available devices include the Thopaz system from Medela and the ATMOS device. These units are portable, battery-powered, and can run on either suction or a digital water-seal equivalent. A retrospective comparison found that patients managed on digital water seal after lung resection had a shorter air leak duration (median two days versus three days on low suction) and shorter overall drainage duration (three days versus five).¹⁹ The objectivity of the readings is arguably the biggest advantage: rather than debating whether a tube is still leaking, the team can look at a flow graph and make a data-driven decision about when to pull the tube. Digital systems also make it easier for patients to mobilize, since they are not tethered to a wall suction unit.

How Chest Drainage Became a Closed System

The water seal concept feels elegantly simple today, but it took centuries to arrive at. Hippocrates described draining pus from the chest in antiquity, but open drainage exposed the pleural space to air and infection, making outcomes grim.²⁰ The breakthrough came in the nineteenth century. In 1871, British physician William Smoult Playfair described subaqueous drainage for treating empyema in children, immersing the end of the drain tube under water to prevent air from entering the chest while still allowing pus to escape. A few years later, German physician Gotthard Bülau independently developed his own closed drainage device with a liquid seal.²¹ The principle they both arrived at, using a column of water as a one-way valve, is the same one sitting at the bedside of every patient with a chest tube today. The engineering has gotten slicker, the materials have improved, and digital sensors have been layered on top, but the core physics of the water seal has not changed in a century and a half.