Clamping a Salem sump nasogastric (NG) tube is a straightforward process, but which lumen you clamp and when you clamp it matters. The tube has two lumens: a large drainage lumen connected to suction and a smaller blue pigtail vent that allows air into the stomach. Each one has different rules, and clamping the wrong one at the wrong time can injure the stomach lining.
How the Two Lumens Work
The Salem sump’s defining feature is its double-lumen design. The larger lumen drains gastric contents when connected to suction. The smaller blue pigtail acts as an air vent, allowing atmospheric air to flow into the stomach and break the vacuum that builds as fluid is pulled out. This air vent mechanism limits excess negative pressure that could cause the stomach lining to get sucked against the drainage holes, damaging the tissue.
Understanding this distinction is essential before you clamp anything. The two lumens serve completely different purposes, and the clamping rules for each reflect that.
Clamping the Primary Drainage Lumen
The main drainage lumen is the one you’ll clamp in most clinical scenarios. The most common reason is a clamping trial: testing whether a patient can tolerate having the tube off suction before it’s removed entirely. In a typical protocol, the tube is clamped after an initial period of decompression (often around two hours). If the patient develops severe nausea or vomiting during the trial, you unclamp the tube and reconnect it to continuous low wall suction right away.
To clamp the drainage lumen, use a smooth, padded clamp or a designated tube clamp placed on the external portion of the large lumen tubing, between the patient and the suction connection. Disconnect the tubing from the suction source after clamping so the suction device isn’t running against a closed line. Keep the clamp visible and easily accessible so it can be released quickly if the patient becomes symptomatic.
Other situations where clamping the drainage lumen comes up include medication administration (clamping briefly after instilling medication so it stays in the stomach) and patient transport, when reconnecting to wall suction isn’t possible.
Never Clamp the Blue Pigtail While Suction Is Running
The blue pigtail vent should not be clamped or sealed off while the drainage lumen is connected to active suction. The pigtail exists specifically to prevent a dangerous vacuum from forming inside the stomach. If you block the air vent while suction is on, there is nothing to relieve the negative pressure. The stomach wall collapses against the drainage holes, and the tissue can be damaged by sustained suction. This is the same mechanism that causes pressure injury to any tissue pulled against a catheter tip.
If the drainage lumen is clamped and suction is disconnected, the blue pigtail does not need to remain open because no vacuum is being generated. In that scenario, you can cap the pigtail to keep it clean. The critical rule is simple: if suction is active, the pigtail stays open.
What to Do When the Blue Pigtail Leaks
Fluid backing up and leaking out of the blue pigtail is one of the most common frustrations with Salem sump tubes, and it tempts people to clamp or cap the vent. Resist that urge. Backflow from the pigtail is almost always a sign that the drainage lumen is partially or fully blocked.
The fix is to address the blockage, not seal off the vent. Disconnect the suction, then flush a bolus of air through the blue pigtail to clear it. You can also irrigate the main drainage lumen with a small amount of normal saline per your facility’s protocol, then reconnect suction. If the tube clogs repeatedly, the problem is often tube size. In adults, an 18 French tube is generally recommended because smaller sizes are prone to clogging and often end up needing replacement anyway.
Some Salem sump kits come with a small anti-reflux valve (a blue or white cap) designed to let air in through the pigtail while preventing gastric contents from flowing out. In theory this solves the leaking problem, but in practice these valves can clog, and they mask the very symptom (backflow) that tells you the tube is blocked. If you use one, check the tube frequently for signs of obstruction, such as decreased drainage output or the patient developing nausea and abdominal distension. Many experienced clinicians prefer to leave the pigtail open and simply place a piece of absorbent padding beneath it to catch any drainage.
If the pigtail continues to leak despite clearing attempts, the tube itself may need to be replaced. Once persistent leaking starts, it tends to continue.
Suction Settings to Know
When a Salem sump is on active suction, the typical order is low intermittent suction. The low range on most wall suction devices runs from 0 to 80 mmHg, with a starting point between 40 and 60 mmHg recommended. Suction should not exceed 80 mmHg. Intermittent suction is preferred over continuous in most cases because the cyclical on-off pattern gives the stomach lining periodic relief from negative pressure, reducing the risk of tissue injury even with the air vent functioning properly.
Step-by-Step Summary for Clamping
- Verify the order. Clamping is done on provider order, whether for a clamping trial, medication administration, or transport.
- Use the right clamp. A smooth or padded clamp prevents damage to the tubing. Hemostats or toothed clamps can crack or puncture the tube.
- Clamp the large drainage lumen only. Place the clamp on the external tubing between the patient’s nose and the suction connection point.
- Disconnect from suction. Once clamped, disconnect the drainage tubing from the suction source so the device isn’t running against a sealed line.
- Cap the blue pigtail if desired. With suction off and the drainage lumen clamped, you can cap the pigtail to keep it clean. If suction is restarted for any reason, uncover the pigtail immediately.
- Monitor the patient. During a clamping trial, watch for nausea, vomiting, or increasing abdominal distension. If any of these develop, unclamp the tube and reconnect to suction.
The core principle is straightforward: the drainage lumen can be clamped when suction is off, and the blue pigtail must stay open whenever suction is on. Everything else follows from that.