The Pre-brief
You are a brand new fellow in the intensive care unit during the month of July when your attending asks you to go assess a patient to see if she is ready for extubation. She is a 45 year old female who was admitted for respiratory failure secondary to angioedema from lisinopril use. You anxiously walk into the room to see her and she is awake, following commands, and has been tolerating a pressure support 5/5 spontaneous breathing trial (SBT) for 45 minutes. You want to extubate, and you go through the points from my previous article, and realize that she is at a high risk for post extubation stridor. What do you do now?
Why do we care about post extubation stridor?
Stridor is produced by the rapid, turbulent flow of air through a narrowed or partially obstructed segment of the extrathoracic upper airway that can mimic wheezing and sometimes sound like a squeak. These areas are the pharynx, epiglottis, and larynx. Structures outside of these areas can include lymph nodes, masses, and esophageal issues as well. Post extubation stridor is responsible for 4-37% of extubation failures, with this range being wide due to lack of studies that have explored this in a standardized way. While the rate of re-intubation in these patients is unknown, about 15% of all re-intubations are due to post extubation stridor or laryngeal edema.
Risk factors for post extubation stridor are excessive airway manipulation (ie: airway surgeries or traumatic intubation), prolonged intubation attempt (greater than 10 minutes), larger endotracheal tubes, intubation lasting longer than 36 hours, agitation while intubated, high cuff pressures, recurrent intubation, female gender, children, trauma patients, short neck, and known airway pathology such as tracheomalacia or tracheal stenosis.
In these instances, and in these instances only, a cuff leak test can be used to predict the risk of post-extubation stridor in patients.
What is the cuff leak test?
Ideally, direct visualization of the airway and vocal cords to assess for edema or laryngeal swelling is the best way to identify those at risk for post extubation stridor. Given the difficulty of doing this while an ETT is in place, the cuff leak is the next best option. It is a bedside assessment used to predict the risk of post extubation stridor in intubated patients. It can be done on most intubated patients, except those who are intubated due to obstruction of a supraglottic structure that is being splinted apart while the endotracheal tube is in.
A proper cuff leak test is done as follows:
- Suction endotracheal and oral secretions and set the mechanical ventilator in the assist control mode with the patient receiving volume cycled ventilation at 10cc/kg ideal body weight.
- With the cuff inflated, ensure the inspiratory and expiratory tidal volumes are similar and record this value.
- Deflate the cuff and record the expiratory tidal volume over the next six breathing cycles or until the expiratory cycle reaches a plateau of volumes.
- Take the average of the three lowest values
- Take the difference between the inspiratory tidal volume from step 2 and the averaged expiratory tidal volume from step 4.
- Take the number from 5 and divide it by the number you obtained in step 2. Ideally, you want this to be 10% or more from the value in step 2, or an absolute value of 110ml difference.
What is the evidence behind this assessment?
A meta-analysis from November 2020 examined 28 studies that were published between 1992-2019. In each of these studies the sample size was small, ranging from 34-543 with a median of 101 patients. The mean duration of mechanical ventilation was 2 to 28 days.
The studies used a range of modalities to do the cuff leak test — ranging from auscultation of air flow to actually measuring it as noted in the steps above. In the quantitative measures, the range of the cuff leak was anywhere from 50ml to 283ml, with a median of 110ml. The modes of ventilator were also different with both assist control mode and spontaneous breathing trial modes used, along with T-pieces.
Once extubated, the prevalence of post extubation airway stridor ranged from 4-37% with a sensitivity of 0.62 and a specificity of 0.87. This means that in patients who have failed the cuff leak test, will have a higher chance of post extubation stridor, whereas patients who pass the cuff leak test may not necessarily do well.
ATS/CHEST guidelines suggest performing a cuff leak test in mechanically ventilated adults who meet extubation criteria and are at high risk of postextubation stridor. This is a conditional recommendation with low certainty in evidence.
What if my patient fails the cuff leak test?
Repeat the test to ensure that your patient has failed. Also keep in mind that the patient can have secretions around the ETT balloon itself or even have too large of an ET tube for their trachea. If these conditions are evaluated and not deemed to be the cause of the failed cuff leak test, give 60 mg IV methylprednisolone, wait 4-6 hours, and extubate without repeating the cuff leak test. Watch the patient carefully for post extubation stridor or respiratory distress, as the complications will happen within a few hours of extubation.
Other treatments that can be used are nebulized epinephrine that works by decreasing laryngeal edema through vasoconstriction, and heliox, which decreases airway resistance. Unfortunately, there is no consensus or strong evidence to support its use. Per ATS/CHEST guidelines, in adults who have failed the cuff leak test, they recommend administration of systemic steroids at least four hours before extubation. This is also a conditional recommendation, but with moderate certainty in the evidence. There is no mention of epinephrine or heliox in these guidelines.
The Debrief
Only do a cuff leak test if your patient is at a high risk for post extubation stridor. If your patient fails the cuff leak test, repeat, and give steroids 4-6 hours prior to extubation and do not repeat the cuff leak test.
References
- De Backer D. The cuff-leak test: what are we measuring?. Crit Care. 2005;9(1):31-33. doi:10.1186/cc3031
- Gerard, Timothy et al. An Official American Thoracic Society/American College of Chest Physicians Clinical Practice Guideline: Liberation from Mechanical Ventilation in Critically Ill Adults. Rehabilitation Protocols, Ventilator Liberation Protocols, and Cuff Leak Tests. Am J Respir Crit Care Med. 2017 Jan 1;195(1):120-133. doi: 10.1164/rccm.201610-2075ST. PMID: 27762595
- Kuriyama, A., Jackson, J.L. & Kamei, J. Performance of the cuff leak test in adults in predicting post-extubation airway complications: a systematic review and meta-analysis. Crit Care 24, 640 (2020).
- Pluijms WA, van Mook WN, Wittekamp BH, Bergmans DC. Postextubation laryngeal edema and stridor resulting in respiratory failure in critically ill adult patients: updated review. Crit Care. 2015;19(1):295. Published 2015 Sep 23. doi:10.1186/s13054-015-1018-2
- Wittekamp, B.H., van Mook, W.N., Tjan, D.H. et al. Clinical review: Post-extubation laryngeal edema and extubation failure in critically ill adult patients. Crit Care 13, 233 (2009).
