Respiratory Therapy Blog

Patients who have an endotracheal tube (ETT) in place are possibly at risk for post-extubation stridor due to things such as airway inflammation, edema, and airway mucosal ulceration. Post-extubation stridor has an incidence that ranges between 2% and 16% in patients that have been intubated for longer than 24 hours. One technique used to attempt to predict the occurrence of post-extubation stridor is the ETT cuff-leak test.

There are two types of cuff leak tests that can be performed, the auscultation cuff leak test and the cuff leak volume test. The auscultation cuff leak test classifies the leak into three categories:

• no leak, where no sound of leak was heard by using stethoscope detection

• mild leak, where a leak is heard using a stethoscope

• significant leak, where the sound of a leak was heard without using a stethoscope

In the cuff leak volume (CLV) test the actual tidal volume at expiration during six consecutive breaths in the Assist Control mode is measured before and after deflation of the ETT cuff, the difference in the tidal volume before and after cuff deflation is the cuff leak volume. This can be shown as an absolute volume or as percentage of tidal volume. When cuff leak volume is less than 140 ml or less than 10-20% the risk for post-extubation stridor is significantly elevated.

Dr. Cheng and colleagues(1) recently looked at IV methylprednisolone to reduce the incidence of post-extubation stridor and they also looked for agreement between qualitative (auscultation) and quantitative (CLV) measurement of cuff leak. They found that 18% of CLV was the optimal predictor for stridor and there was excellent agreement between the auscultation and CLV tests. There does appear to be a lot of false positives (cuff leak predicts stridor but it does not always occur), in 128 patients with a CLV of less than 24%, 70% of patients did not develop stridor and 81% did not require reintubation.

There seems to be a nice correlation between auscultation and CLV tests in assessing for the possibilty of post-extubation stridor. I tend to use the auscultation cuff leak test solely and so do alot of my colleagues. Although it is somewhat subjective it is nice to know that it correlates well with the CLV test.

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(1) Cheng KC, Hou CC, Huang HC, Lin SC, Zhang H. Intravenous injection of methylprednisolone reduces the incidence of postextubation stridor in intensive care unit patients. Crit Care Med. 2006 May;34(5):1345-50.