The Cuff Leak Test: A New Appraisal of an Old Technique. Who Benefits?

Cuff leak tests have been performed on countless intubated patients for decades. Despite this widespread prior use, the test remains controversial. The controversies surrounding a cuff leak test focus mainly on the following areas: who exactly should be tested, how to best perform the test, and what to do with the result? The study by Kallet and Lipnick¹ in this issue of Respiratory Care provides important insights into these questions.

The original cuff leak test was developed by pediatric intensivists to determine when to extubate children with croup during a 3-month croup epidemic in Ontario, Canada.² The researchers concluded that the children could be safely extubated if they had decreased secretions and an “audible air leak” with either coughing or with “a positive pressure insufflation of <40 cm H₂O.”² Since then, multiple studies have addressed the question of whether the test is useful in the adult patient population and whether this test can be standardized and the leak quantified. It is important to note that a positive study is defined as no leak.¹ Most studies reported widely varying and generally lower positive predictive values of cuff leak tests (that is, a positive study [no leak] is not particularly predictive of extubation failure). The reported negative predictive values have consistently been higher.

Kallet and Lipnick¹ build on these previous studies by standardizing who should be included and by protocolizing the actual cuff leak test. By using screening tools to identify patients at high risk for postextubation stridor in a predominantly trauma and neurosurgical patient population, these researchers categorized subjects to be at high, moderate, and low risk for postextubation stridor. The current study determined that the risk of stridor was almost 3-fold higher in subjects who were at high risk and had no test performed than in subjects at high risk and with a negative leak test. These data support recommendations to use a screening tool to identify a high-risk population in whom to perform the leak test.³

A qualitative cuff leak test is part of the extubation protocol in many hospitals around the country. However, the use of the derived information has been discussed in meetings, papers, and editorials, and has remained controversial due to its low positive predictive value. Investigators have hoped that the use of quantitative approaches might improve the usefulness of the cuff leak test. Kallet and Lipnick¹ modified a cuff leak test protocol by Miller and Cole⁴ as follows. The investigators used standard volume-controlled ventilation settings. The researchers performed a cuff leak test with the patient in a standardized position. They measured only the change in expired tidal volume between endotracheal tube inflation and deflation. The cutoff of 110 mL as a cuff leak was identical to the cutoff in the study by Miller and Cole⁴ (Interestingly, their ad hoc analysis by using 100 mL as a cutoff did not significantly alter the results.). The advantage of this standardized approach is that it can be uniformly applied to all ventilators. However, one significant drawback to this protocol seems to be the need for sedation to achieve a Richmond Agitation-Sedation Scale score of < –1 to allow volume-controlled ventilation. Sedation before extubation might delay extubation and have unintended hemodynamic and neurologic consequences.

Should the work by Kallet and Lipnick¹ change our practice? Based on their work and previous recommendations, not every intubated patient should undergo a cuff leak test. A standardized screening process plus a protocolized cuff leak test approach however seems to make sense to us because it also allows the practitioner to use other tools to further decrease the risk of stridor, including patient positioning, steroids, and fluid management. We, however, do have some reservations with regard to the proposed standardized cuff leak test protocol. Ideally, the cuff leak test should be included in the extubation protocol, negating the need for additional sedation. Further research might explore how to best quantify leak tests in patients who are spontaneously breathing. Finally, the presence of a positive leak test (ie, no leak) leads to further investigation, which has also not been standardized. This further evaluation could include direct or indirect laryngoscopy to visualize the glottis to aid decision-making.

Overall, it is unlikely that a single test will replace expert clinical assessment, which may include additional imaging and/or visualization. However, given its excellent negative predictive value, the cuff leak test may be a useful tool to help expedite safe extubation. The screening tool, furthermore, can readily identify patients at risk for postextubation stridor and easily identify who benefits from a cuff leak test and identify patients who warrant further comprehensive expert assessment. We congratulate Kallet and Lipnick¹ for addressing these questions and for an excellent study that contributes to helping us optimize patient care.