You should occlude the side opening (suction port) of a suction catheter only during withdrawal, never during insertion. The catheter goes in without suction, and you apply suction by covering the port with your thumb as you gently pull the catheter back out. This single timing rule prevents most of the serious complications associated with airway suctioning.
Why Only During Withdrawal
The side port on a suction catheter acts as a valve. When it’s open, air flows freely through the port and no negative pressure reaches the catheter tip. When you place your finger or thumb over it, you seal the system and activate suction at the tip.
Applying suction during insertion would drag the catheter tip against the airway lining as it advances, causing direct mucosal trauma that can lead to bleeding, ulceration, or inflammation. The negative pressure can also pull airway tissue into the catheter opening, injuring delicate structures deeper in the airway. Beyond tissue damage, suctioning on the way in disrupts gas exchange, potentially collapsing small air sacs in the lungs (atelectasis) and dropping oxygen levels. In pediatric and critically ill patients especially, this can trigger a dangerous drop in heart rate through stimulation of the vagus nerve.
By keeping the port open during insertion, you’re essentially just sliding a passive tube into position. No suction force is applied, no tissue gets pulled, and the airway stays undisturbed until you’re ready to withdraw.
The Full Suctioning Sequence
Understanding port occlusion makes the most sense within the complete technique:
- Pre-oxygenate. Deliver supplemental oxygen before the suctioning pass. This builds an oxygen reserve because the procedure temporarily interrupts normal breathing.
- Insert without suction. Using a clean, non-touch technique, gently advance the catheter to a pre-measured depth. The side port stays uncovered the entire time.
- Occlude the port and withdraw. Place your thumb over the side opening to activate suction. Slowly pull the catheter out while gently rotating it between your fingers. The rolling motion helps the catheter collect secretions from all sides of the airway without lingering on one spot.
- Limit each pass to 15 seconds or less. The American Association for Respiratory Care recommends keeping the total suctioning event under 15 seconds. Some pediatric guidelines recommend even shorter passes of 5 to 10 seconds. Start timing from when you occlude the port, not from when the catheter enters the airway.
Open vs. Closed Suction Systems
The principle is the same whether you’re using an open (single-use) catheter or a closed inline system, but the mechanics differ slightly.
With an open catheter, you physically cover a small hole on the catheter’s connector with your thumb. Thumb on means suction is active. Thumb off means suction is off. This gives you direct tactile control.
Closed suction systems, sometimes called inline or Ballard catheters, stay connected to the ventilator circuit throughout the procedure. Instead of a side port you cover with your thumb, these systems use a thumb valve or button you press down to activate suction. You push the valve during withdrawal only, following the same timing rule. The advantage is that the patient stays on the ventilator during the procedure, which helps maintain oxygen levels and reduces infection risk since the catheter stays inside a protective sleeve.
What Happens if Timing Is Wrong
Occluding the port at the wrong moment, whether during insertion or for too long during withdrawal, increases the risk of several complications. Negative pressure applied directly to airway tissue causes mucosal injury ranging from mild irritation to bleeding and structural damage. Repeated improper technique can lead to chronic inflammation or ulceration at the same sites.
The oxygen-related risks are equally serious. Suctioning pulls air out of the lungs along with secretions. When no secretions are present, or when suction is applied for too long, the negative pressure collapses small airways and reduces the lung’s working surface area. Oxygen saturation drops, sometimes significantly. In patients already on the edge of adequate oxygenation, this can become clinically dangerous within seconds.
Vagal stimulation is another concern. The vagus nerve runs near the trachea, and mechanical irritation combined with negative pressure can trigger it, slowing the heart rate. This bradycardia response is more pronounced in children and infants but can occur in adults as well. Keeping the suction pass brief and applying negative pressure only during a smooth, rotating withdrawal minimizes this risk.
Insertion Depth and When to Start Withdrawing
Before you occlude the port, you need to know the catheter is at the right depth. The standard approach is to pre-measure the catheter against the airway tube so you know exactly how far to advance it. For endotracheal or tracheostomy suctioning, the catheter typically advances to just beyond the tip of the artificial airway, not deep into the trachea itself.
Deep suctioning, where the catheter passes well beyond the tube tip until you feel resistance from the airway wall, carries a higher risk of mucosal injury, bleeding, and vagal stimulation. Most current guidelines favor shallow or pre-measured suctioning depth for routine use. Once the catheter reaches the target depth, you immediately begin occluding the port and withdrawing. There’s no benefit to leaving the catheter sitting in place.
Practical Tips for Clean Technique
Keep your dominant hand sterile and use it to handle the catheter. Your non-dominant hand controls the suction port and tubing connections. This way you can smoothly cover and uncover the port without contaminating the catheter itself.
If you need more than one pass, allow the patient time to recover between attempts. Re-oxygenate before each subsequent pass and reassess whether additional suctioning is actually needed. Unnecessary passes increase cumulative trauma and oxygen loss without benefit. The goal is to clear secretions that the patient can’t move on their own, not to keep the airway perfectly dry.