When intubating, we all know to check the depth of the endotracheal tube. Most people believe this is just to ensure that the tube is not too deep and therefore causing a mainstem intubaton: intubating just one bronchus and therefore only one lung. However, there are significant risks with having the tube too shallow as well.
Cuff Above The Cords
In addition to ensuring that the tube is not too deep, also make sure that the cuff is not too high, and that it’s below the cricoid ring. Having the cuff above the cords happened to me just the other day and even I was fooled for a few minutes into thinking that I had a cuff leak.
I had all of the classic signs of a cuff above the cords:
- There was a persistent leak despite the fact that I keep adding air to the cuff balloon.
- Adding more air to the cuff made the leak worse.
- The pilot balloon became increasingly distended, tense, and held pressure.
- I could ventilate the patient because the tube tip was in the trachea, but I wasn’t able to provide a full tidal volume because pressurizing the lungs caused the cuff to pop up off the trachea, releasing the pressure.
- When I checked with laryngoscopy, the cuff was above cords.
Obviously there was significant risk of extubation because only the tip of the tube was through the glottis.
Differential Diagnosis For a Persistant Cuff Leak
There are several other situations that will cause a leak around the endotracheal tube cuff. These are:
- the cuff needs more air to make the seal within the trachea
- a hole in the cuff
- a faulty (leaky) pilot balloon
- a cuff above the cords: risk of unplanned extubation high
If adding a little more air to the cuff fixes the leak and the depth looks correct, most likely there was just an inadequate seal. With a faulty cuff or pilot balloon, reinflation of the pilot balloon temporarily fixes the problem, but the pilot balloon becomes soft again as the cuff deflates. If the pilot balloon is faulty, attaching a closed stopcock after reinflation will often solve the problem. If the cuff itself is leaking, the tube will need replacement.
What To Do If The Cuff Is Above The Cords:
When the cuff is above the cords, only the tip of the tube is though the cords. The tube can pop out of the larynx and into the esophagus if the tube bows in the posterior pharynx while you are pushing the tube deeper. To avoid this, I recommend performing laryngoscopy to push the tube deeper under direct vision. If you have an awake patient or your patient is in an awkward position (such as prone), this may not always be feasible. Proceed carefully and be aware that the risk of accidental extubation is higher if you push the tube blindly. To push the tube deeper:
- Make sure you have the equipment for reintubation immediately available.
- Suction the patient’s mouth.
- Untape the tube and deflate the cuff. It may take several aspirations if the balloon has become overdistended with the attempts to seal the leak. Hold the tube firmly during this process.
- Gently advance the tube to the proper depth.
- Reinflate the cuff.
- Immediately reverify proper placement.
- Secure the tube.
Cuff Inside the Cricoid Ring
If the cuff sits partially inside the rigid cricoid cartilage, it can press on and potentially injure the recurrent laryngeal nerves which run under the mucosa inside the ring. Recurrent laryngeal injury can cause potentially permanent vocal cord paralysis. Vocal cord paralysis can be a terrible injury causing permanent hoarseness. If injury is bilateral, the patient can suffer from significant airway obstruction because the cords rest in the cadaveric position: partially closed in the midline.
Predispostions For Having A Cuff Inside the Cricoid
There are several situations that can increase the risk of leaving the cuff inside the cricoid ring.
- Failure to insert the tube to the correct depth for that patient.
- Cuff over distention
- even if most of the cuff is below the ring, if it’s close enough to the ring it can spread into the ring.
- Shorter than normal tube.
- Sometimes we will use a small diameter pediatric tube, such as a 5 or 5.5 cuffed tube in an adult to facilitate oropharyngeal surgery or to accommodate patient pathology can place the cuff too high in the larynx.
- Pediatric tubes are shorter than standard adult tubes, so they appear to be inserted to the correct depth based on how much tube exits the mouth. However, verifying the depth in cm at the teeth will reveal the problem. Often the longer Microlaryngeal Tracheal Tube (MLT) style tubes are chosen to avoid this situation.
- Allowing the tube to overly the tongue
- The tube may be taped at the correct depth at the teeth, but the fact that several cm of it overly the tongue means that less of it is inside the trachea. Not only does this position risk leaving the cuff inside the cricoid ring, the patient can push the tube out more easily with their tongue.
- Very tall adults (e.g. 6’4″ with tube only inserted to 21 cm)
- A tube placed higher in the trachea in a patient whose head is then tilted back.
- The tube tip follows the direction of the nose. Tilting the head back raises the tube. Tilting the head forward causes the tube to sink deeper into the trachea (potentially causing mainstream intubation)
Depth Of Insertion Guidelines
The only formula for depth of insertion is for pediatric intubation. Typically for children we use: depth of insertion in cm = (age of child in years) /2 + 12
For a typical adult we insert to 21-22 cm at the teeth. Always check breath sounds because shorter adults may well be more shallow. Very tall adults should have the tube inserted a bit deeper to ensure the cuff is below the cricoid.
As you can see, verifying proper placement of the endotracheal tubes does not stop at making sure the tube is in the trachea, or making sure that a mainstream intubation has not occurred. It also requires checking to see if the tube tip is too high in the trachea. Failure to insert the tube deeply enough risks accidental extubation and permanent injury to the recurrently laryngeal nerve.
May the force be with you
Christine E. Whitten MD