Despite their role as life-saving procedures, endotracheal intubation and mechanical ventilation can cause severe complications. A significant factor in extubation failure is laryngeal edema and airway obstruction after extubation.
Its clinical symptom, post-extubation stridor, has a documented incidence of 2-26% and patients commonly require reintubation.1 The most used screening test for airway edema and post-extubation airway obstruction is a cuff-leak test (CLT), a test which includes deflating the endotracheal tube (ETT)balloon and listening for air flowing around the ETT. The positive cuff-leak test can, in a high percentage, predict post-extubation airway obstruction. However, due to its low to moderate sensitivity, a negative test cannot exclude potential complications after the patient has been extubated.
In this article, we’ll discuss why and how the cuff-leak test should be used to predict post-extubation stridor, as well as extubation success or failure.
Endotracheal intubation and laryngeal edema
Endotracheal intubation is a frequent invasive procedure performed in the intensive care unit, (ICU) as well as in the operating room2.
Although a potentially life-saving procedure, especially for a patient who suffers from respiratory distress, local complications sometimes happen. Although endotracheal tubes are composed of flexible polyvinyl chloride, which has low-pressure and high-volume cuffs and is less likely to lead to injury, airway lesions can still be very commonly encountered3.
Even when endotracheal intubation is successfully performed, without mechanical injuries, the endotracheal tube (ETT) itself can cause complications. The endotracheal tube increases pressure against the posterior larynx, causing polymorphonuclear infiltration, fibrinous exudation, and damaging the medial surface of the vocal cords and arytenoid cartilages. This can lead to laryngeal edema (LE) and ulceration4,6.
LE is caused by substantial granulocytic infiltration to the injured airway. Airway constriction and increased airflow velocity are two consequences of LE. Stridor and respiratory distress may occur if the lumen is narrowed by more than 50%. According to several observational studies, 3.5% of LE patients must be reintubated. Reintubation itself may be linked to morbidity and mortality for various reasons2,4,6 Because of this, LE is a significant factor in post-extubation stridor, extubation failure and the need for reintubation7.
CLT as a predictor of successful extubation
The most used screening test for airway edema and post-extubation airway obstruction is a cuff-leak test (CLT). The test includes deflating the ETT balloon and either listening for air flowing around the ETT or measuring the air leak's volume quantitatively. Air leakage around the ETT implies that the airway is open (i.e., a passed CLT). However, a small air leak or the lack of one (i.e., a failed CLT) may imply edema, which could obstruct the airway after extubation2,5,6,7,8.
The extubation outcomes of 6,583 patients, who had planned extubations, were examined in the study done by Lai et al., 2016, which is the largest of its kind. According to this retrospective analysis, the overall extubation failure rate was 6.1%. Researchers also demonstrated that extubation failure was substantially correlated with age, gender, illness severity, level of consciousness, rapid shallow breathing index (RSBI), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and CLT.
Additionally, they discovered three independent predictors of effective extubation, including the CLT, MEP, and RSBI. CLT, MEP, and RSBI are three predictors which stand for upper airway patency, cough strength and respiratory function, respectively. Therefore, the extubation success rate should be high in patients who passed the CLT, had a high MEP and had a low RSBI9.
In the same study, researchers replaced the conventional quantitative measurement of the cuff-leak volume with a semiquantitative method (auscultation CLT). Most significantly, they demonstrated that auscultation CLT is independently and significantly related to the success of extubation. The extubation success rate was approximately twice as high for individuals with a CLT of 2+ (audible flow without a stethoscope) than for those with a negative CLT (no audible flow with a stethoscope). Additionally, researchers discovered that a greater proportion of the 80 patients experiencing extubation failure due to upper airway obstruction were classified as CLT negative (n=17, 45.9%) or CLT positive (n=26, 28.3%) than any other group with failed extubation9.
CLT as a predictor of airway obstruction, edema and required reintubation
Another study, by Keeratichananont et al. in 2012,revealed that the cuff-leak volume was less than 114 ml, indicating a difference of 4 ml from the reported 110 ml in the Kriner's 2005 study4,10. This cuff-leak volume is similar but higher in sensitivity, specificity, positive predictive value and negative predictive value in predicting post-extubation stridor. As a result, the measurement of the cuff-leak volume may be a good indicator of upper airway blockage, which may be related to airway damage. However, the quantified volume of the cuff-leak test can be an indirect predictive factor and can only partially correlate with or imply laryngeal edema and successful extubation4.
In an indirect comparison analysis in 2011,Zhou et al.discovered that the cuff-leak test successfully identifies adult patients at high risk for post-extubation airway problems and that cuff-leak test screening decreases the frequency of post-extubation laryngeal edema but not that of reintubation8.
Finally, a systematic review and meta-analysis by Kuriyama et al. in 2020 included studies that investigated the cuff-leak test's diagnostic accuracy as a predictor of post-extubation airway obstruction and reintubation7. They included 28 studies involving 4,493 extubations. The meta-analysis concluded that the cuff-leak test has excellent specificity but moderate sensitivity for assessing post-extubation airway obstruction7.
Use of the CLT globally
In 2021, Lewis et al. conducted the first international survey that examined the belief of the intensive care physician about the utility and accuracy of the CLT in ICU patients5. The study included 1184 ICU physicians from 17 countries worldwide. 59% of the 1184 intensivists surveyed said they would not perform a CLT before extubation if the patients were not at risk for laryngeal edema. The practice of using CLT prior to extubation varied and was related to the geographic areas of the intensivists surveyed.5Many of the respondents (63.1%) agreed that a passed CLT was a useful predictor of a patent airway, however, a smaller percentage (41.8%) felt that reintubation could be predicted by a failed CLT.5
The majority (62.2%) of the 878 intensivists who claimed to use the CLT in their practice utilized a bedside auscultation technique to find air leaks. The minority (34.4%) used a quantitative evaluation of the ventilator's tidal volumes to identify air leaks.
When patients fail the CLT, most intensivists who performed the test (56.5%) reported that they had delayed extubation (i.e., no or negligible leak identified). Additionally, 61.8% would recommend systemic corticosteroids if a patient failed a CLT. The majority (61.0%) of respondents who reported prescribing corticosteroids said they did so in repeated doses over 12–24 hours5.
Conclusion
Although most of the studies mentioned above showed that a positive cuff-leak test could, in a high percentage, predict post-extubation airway obstruction or laryngeal edema, due to the low to moderate sensitivity, a negative test cannot exclude potential complications after extubating a patient. Due to its high specificity, researchers suggest that clinicians can use CLT in their daily clinical practice. However, it should not be used as the sole predictive factor for airway obstruction or incidence of reintubation after the patient's extubation.
References
- Shinohara, M., Iwash*ta, M., Abe, T., & Takeuchi, I. (2020). Risk factors associated with symptoms of post-extubation upper airway obstruction in the emergency setting.The Journal of international medical research,48(5), 300060520926367.https://doi.org/10.1177/0300060520926367
- Argalious, M. Y. (2012). The Cuff Leak Test: Does It “Leak” Any Information? Respiratory Care, 57(12), 2136–2137.https://doi.org/10.4187/respcare.02193
- Schnell, D., Planquette, B., Berger, A., Merceron, S., Mayaux, J., Strasbach, L., Legriel, S., Valade, S., Darmon, M., & Meziani, F. (2019). Cuff Leak Test for the Diagnosis of Post-Extubation Stridor: A Multicenter Evaluation Study. Journal of Intensive Care Medicine, 34(5), 391–396. https://doi.org/10.1177/0885066617700095
- Keeratichananont, W., Limthong, T., & Keeratichananont, S. (2012). Cuff leak volume as a clinical predictor for identifying post-extubation stridor. Journal of the Medical Association of Thailand = Chotmaihet Thangphaet, 95(6), 752–755.
- Lewis, K., Almubarak, Y., Hylander Møller, M., Jaeschke, R., Perri, D., Zhang, Y., Du, B., Nishida, O., Ntoumenopoulos, G., Saxena, M., Truwit, J., Young, P. J., Alshamsi, F., Arabi, Y. M., Rochwerg, B., Karachi, T., Szczeklik, W., Alshahrani, M., Machado, F. R., … Alhazzani, W. (2021). The cuff leak test in critically ill patients: An international survey of intensivists. Acta Anaesthesiologica Scandinavica, 65(8), 1087–1094.https://doi.org/10.1111/aas.13838
- Lewis, K., & Alhazzani, W. (2017). The cuff leak test prior to extubation: A practice based on limited evidence. Saudi Critical Care Journal, 1(6), 22.https://doi.org/10.4103/sccj.sccj_27_17
- Kuriyama, A., Jackson, J. L., & Kamei, J. (2020). Performance of the cuff leak test in adults in predicting post-extubation airway complications: a systematic review and meta-analysis. Critical Care, 24(1), 640.https://doi.org/10.1186/s13054-020-03358-8
- Zhou, T., Zhang, H.-P., Chen, W.-W., Xiong, Z.-Y., Fan, T., Fu, J.-J., Wang, L., & Wang, G. (2011). Cuff-leak test for predicting postextubation airway complications: a systematic review. Journal of Evidence-Based Medicine, 4(4), 242–254.https://doi.org/10.1111/j.1756-5391.2011.01160.x
- Lai, C.-C., Chen, C.-M., Chiang, S.-R., Liu, W.-L., Weng, S.-F., Sung, M.-I., Hsing, S.-C., & Cheng, K.-C. (2016). Establishing predictors for successfully planned endotracheal extubation. Medicine, 95(41), e4852. https://doi.org/10.1097/MD.0000000000004852
- Kriner, E. J., Shafazand, S., & Colice, G. L. (2005). The endotracheal tube cuff-leak test as a predictor for postextubation stridor. Respiratory Care, 50(12), 1632–1638.
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