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Safety Letter

Patient Safety Letter

This is to document the harm endotracheal tubes and endotracheal tube (ETT) pilot balloons can cause patients, even after short surgeries, and the need for new standards of care in anesthesia. The new standards that are needed are:

1. Check and document cuff pressure with each and every intubation.

2. Base endotracheal tube sizing on the diameter of the patient’s trachea, not “routine” practice.  This will result in the use of a size 6.0 or 6.5 for women.

Although marketed as “low” pressure, the ETT is easily converted to a “high” pressure cuff if the pilot balloon is over-inflated.  This manual over-inflation can generate pressures against the tracheal wall that exceed 120 cm H2O pressure.  Since tracheal perfusion pressure is around 30 cm1, anything above this places the patient at risk of tracheal ischemia, recurrent laryngeal nerve damage and subglottic stenosis (SGS)2.  Similarly, if an endotracheal tube that is too large is used, the same complications are possible3.

Routine practice today is to inflate the pilot balloon by the injection and palpation method.  All research shows that this technique is ineffective and results in the majority of pressures being too high.  Currently, there are no standards in anesthesia that regulate inflation technique of the pilot balloon.  Without regulation, anesthesia providers inject as much air as they want, resulting in pressures that can exceed 120 cm H2O pressure.  (A standard manometer only goes to 120 so it is impossible to discern the true pressures ― they could exceed 300!)  Since tracheal perfusion pressure is around 30 cm H2O, anything above this may cause tracheal ischemia, tracheal necrosis, recurrent laryngeal damage, and, ultimately, subglottic stenosis.  All studies show this damage may begin within 15 minutes of high pressure, and not only with the prolonged intubation as historically thought4, 5, 6

A second routine practice is to use a size 7.0 ETT for women.  There is no research to support this practice.  The true size of the 7.0 ETT is the outer diameter of 9.5 mm.  Basic anatomy demonstrates the diameter of some women’s tracheas could be as small as 6.6 mm to 8.0 mm7.  Inserting a size 7 (inner diameter) ETT in a small trachea and then using the injection and palpation technique of cuff inflation could result in the damage to the trachea that leads to subglottic stenosis.

It is unknown how long subglottic stenosis from short term intubations takes to narrow to the critical diameter of 4-5 mm, where shortness of breath at rest occurs.  It could narrow at a rate of 0.2 to 0.5 mm/year and therefore take years for life-threatening symptoms to appear.  In a review of literature on the causes of SGS8,9,10,11, none has documented the cuff pressure of any previous intubation.  Tracheal ischemia begins at around 30 cm H2O pressure and unless the cuff pressure of any previous intubation was documented and shown to be below this, it cannot be ruled out as a cause.


Patients with post-intubation SGS are usually misdiagnosed and incorrectly treated for years prior to receiving the correct diagnosis.  They are usually first diagnosed with gastric reflux and then with asthma.  Some patients are even given the diagnosis of “panic attacks” when they show up in emergency rooms struggling to breathe.  When the correct diagnosis is finally made, a review of their history is done, the intubation is dismissed as having been “too long ago” to be the causative factor, and the patient is labeled idiopathic.  All research, however, points to the intubation as the most probable cause.  The symptoms were there for years; the patient was just misdiagnosed.  Dikkers correlated the development of SGS to an intubation that occurred 20 years before12.

The accompanying letter is from a patient who developed SGS post-intubation, and it is typical of the timeline of this complication.  She says:

I am a 40 year old attorney, wife and mother from Wausau, Wisconsin.  I had a 35 minute intubation for a minor surgery in 2004.  I was 5'5" and weighed 130 pounds.  My anesthesia records indicate that a size 7 tube was used and that cuff pressures were not monitored.  When I woke up I remember coughing very hard and I had a sore throat.  
I began having symptoms of wheezing and shortness of breath with exertion in 2008.  I was misdiagnosed as having asthma for several years. I was short of breath walking up stairs and had an audible wheeze during conversation.  By the time I was finally diagnosed in February, 2011, my airway was reduced to the size of a McDonald’s straw. In the two years since my diagnosis I underwent three dilatation surgeries to open my airway.  I was told that I would continue to need these dilatations every 6-12 months for the rest of my life and that I had a 50% likelihood of needing a tracheostomy during my lifetime.  I underwent a tracheal resection surgery in March 2013 at which time three tracheal rings including my cricoid were removed

The cost of this condition is tremendous.  My medical expenses were approximately $215,000.  In addition, I had to pay for the travel expenses of traveling from Wisconsin to Boston three times.  I missed 13 weeks of work.  This does not include the emotional toll this condition has had on me13.  This could have been prevented by simply checking the pressure and using a smaller tube.

Every day that routine practices are allowed to continue is another day patients are exposed to harm from high cuff pressures and large ETTs.  If you care to read about the real damage that has been done to these patients’ lives, you can read the communications from the online SGS support groups.  I cannot imagine how any organization could ignore the suffering documented there.  The financial, emotional and physical toll on patients from the stenosis and its treatment is unimaginable.

Again, to protect patients from harm, two new standards need to be adopted:

1. Check and document cuff pressure with each and every intubation.

2. Base endotracheal tube sizing on the diameter of the trachea, not “routine” practice. This will result in the use of a size 6.0 or 6.5 for women.

Just as we pad and protect the extremities and nerves with each and every surgery, we must also protect the trachea.  Please help keep patients safe and free of preventable harm from routine endotracheal intubations.

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