Assessment of a three-chamber chest drainage system
The key to this question is separating what is
normal from what signals a problem. In a wet suction system, the
water-seal chamber and the
suction-control chamber each tell a different story, and the nurse must read both together.
Tidaling — the fluid rising with inspiration and falling with expiration — is an expected finding when the chest tube is patent and the system is open to the pleural space. During inspiration, intrapleural pressure becomes more negative, which pulls fluid up the water-seal tube; during expiration, pressure rises and the fluid falls. This oscillation confirms that the drainage system is communicating with the pleural cavity and is not blocked. The absence of tidaling would be more concerning, as it could indicate a kink, clot, or lung fully re-expanded and occluding the tube openings.
The intermittent bubbling in the water-seal chamber when the client coughs is also expected in a pneumothorax.
Coughing raises intrathoracic pressure and forces residual air out of the pleural space through the water seal, producing a brief burst of bubbles. This is air leaving the pleural space, not an air leak. An air leak would present as
continuous bubbling in the water-seal chamber, occurring throughout the respiratory cycle and not only with coughing or forced exhalation.
The gentle, continuous bubbling in the
suction-control chamber is the expected sign that wet suction is functioning at the prescribed level of
20 cm H2O. In a wet suction system, the depth of the water column in the suction-control chamber determines the amount of suction applied; continuous bubbling indicates that the suction is actively drawing air through that water column. If the suction-control chamber were not bubbling, suction would not be working.
| Chamber | Expected finding | Abnormal finding |
|---|
| Water-seal chamber | Tidaling with respiration; intermittent bubbling with cough or exhalation while pneumothorax is resolving | Continuous bubbling (air leak); absent tidaling (obstruction or lung occluding tube) |
| Suction-control chamber | Gentle continuous bubbling while suction is on | No bubbling (suction not functioning); vigorous bubbling (suction may be set too high) |
| Collection chamber | Drainage amount monitored; level marked | Sudden increase in bright red drainage (hemorrhage) |
Watch out! Continuous bubbling in the water-seal chamber is the hallmark of an air leak — either from the patient’s pleural space or from a loose connection in the tubing. To locate the source, briefly clamp the tube near the insertion site: if bubbling stops, the leak is inside the patient; if bubbling continues, the leak is in the tubing or drainage unit.
Key point! Tidaling stops when the lung fully re-expands or when the tube is occluded. Always correlate the water-seal findings with the client’s respiratory status, breath sounds, and chest imaging rather than interpreting the chamber in isolation.
The scenario describes a
22-year-old tall, thin male smoker, which is the classic demographic for a
primary spontaneous pneumothorax due to rupture of subpleural blebs. Six hours after chest tube insertion, the lung is still in the process of re-expanding, so intermittent air evacuation with coughing and preserved tidaling are entirely consistent with a functioning drainage system actively removing residual pleural air. The combination of findings — tidaling, cough-induced bubbling, and continuous suction-control bubbling — represents the expected pattern while a pneumothorax is draining.