|Year : 2017 | Volume
| Issue : 6 | Page : 22-24
The cuff leak test prior to extubation: A practice based on limited evidence
Kim Lewis1, Waleed Alhazzani2
1 Department of Medicine, McMaster University, Hamilton, Ontario, Canada
2 Department of Medicine, McMaster University; Department of Health Research Methods, Evidence and Impact, McMaster University; Guidelines in Intensive Care, Development and Evaluation (GUIDE) Group, McMaster University, Hamilton, Ontario, Canada
|Date of Web Publication||23-Nov-2017|
Department of Medicine, McMaster University, Hamilton, Ontario
Source of Support: None, Conflict of Interest: None
Endotracheal intubation and mechanical ventilation are lifesaving interventions that are commonly performed in the intensive care unit (ICU). The trauma of endotracheal intubation itself, the prolongued pressure exerted by the endotracheal tube on the larynx, and miscellaneous factors such as fluid overload can result in laryngeal edema (LE). Extubation of a patient with undiagnosed LE can results in respiratory failure secondary to an upper airway obstruction and may require reintubation. Respiratory failure requiring reintubation is associated with morbidity and mortality. The cuff leak test (CLT) is the only method intensivists use to predict the presence of LE. Despite the CLT's first description in 1988, the correct way to interpret the results (either qualitatively or quantitatively) is unknown, and its diagnostic accuracy has been called into question. In fact, the CLT could be detrimental to patients if it has a high false positive rate (i.e. no air leak is detected indicating LE when none actually exists). Incorrectly diagnosing patients with LE may result in prolongued mechanical ventilation that predisposes patients to barotrauma, ventilator-associated infections, exposure to systemic steroids, and a prolongued stay in the ICU. Given the paucity of data, the Cuff Leak and Airway Obstruction in Mechanically Ventilated ICU Patients (COMIC) research group is conducting a survey to understand international practice surround the use of the CLT prior to extubation, as well as a randomized controlled trial that will capture the accuracy of the test and determine the bet method to measure cuff leak.
Keywords: Airway obstruction, cuff leak test, ICU, laryngeal edema
|How to cite this article:|
Lewis K, Alhazzani W. The cuff leak test prior to extubation: A practice based on limited evidence. Saudi Crit Care J 2017;1, Suppl S2:22-4
|How to cite this URL:|
Lewis K, Alhazzani W. The cuff leak test prior to extubation: A practice based on limited evidence. Saudi Crit Care J [serial online] 2017 [cited 2021 Jan 28];1, Suppl S2:22-4. Available from: https://www.sccj-sa.org/text.asp?2017/1/6/22/219133
| Introduction|| |
While endotracheal intubation and mechanical ventilation are lifesaving interventions, they can be associated with serious complication such as laryngeal edema (LE). LE is thought to be caused by marked granulocytic infiltration to the traumatized airway. LE can result in airway narrowing and increased airflow velocity, a narrowing of the lumen by ≥50% may result in stridor and respiratory distress. Observational studies showed that about 3.5% of patients with LE will require reintubation. For various reasons, reintubation itself can be associated with morbidity and mortality.
Unfortunately, direct visualization of the larynx is difficult in intubated patients. Therefore, clinicians depend on surrogate measures that could indicate airway narrowing such as the cuff leak test (CLT). In this concise review, we aim to discuss the current evidence and guidelines, evidence gaps, and recommendations moving forward.
| Description of the Cuff Leak Test|| |
The CLT was first described in 1988 to screening for airway edema prior to extubation. This easy to perform, noninvasive test involves deflating the balloon cuff on the endotracheal tube (ETT) and observing whether the patient can breathe around it. Detection of air movement auscultation suggests that the airway is patent. A complete absence or reduction in leak would raise the concern of LE.
Miller and Colequantitatively defined the CLT. They assessed the difference between the inspiratory tidal volume and average expiratory tidal volume with a deflated ETT cuff. The positive predictive value for postextubation stridor was 80% if the cuff leak was <110 mL, and the negative predictive value was 98% if the cuff leak was >110 mL.
Another method to quantify the cuff leak is by the proportion of change in tidal volumes with and without the balloon inflated which is described as follows:
End tidal volume balloon inflated (ETVBI) − ETV balloon deflated]/ETVBI × 100%.
Regression analysis of the diagnostic thresholds failed to identify a specific threshold effect.
| Current Evidence|| |
There are conflicting results on the utility and diagnostic accuracy of the CLT. To date, there are 14 observational studies that either examined reintubation rates or rates of postextubation stridor.,,,,,,,,,, Two meta-analyses of these studies examined the diagnostic accuracy of a CLT., One meta-analysis reports that a failed CLT is insensitive but it is a specific predictor of LE (sensitivity and specificity 0.56; 95% confidence interval [CI] 0.48–0.63 and 0.92, 95% CI: 0.90–0.93; respectively) and reintubation (sensitivity and specificity for reintubation 0.63, 95% CI: 0.38–0.84 and 0.86, 95% CI: 0.81–0.90; respectively). The second meta-analysis also states that the failed CLT was associated with postextubation LE, particularly in patients with more than 5 days' duration of intubation (odds ratio [OR] = 2.09, 95% CI: 1.28–2.89), but was not associated with higher odds of reintubation (OR = 0.94, 95% CI: 0.32–1.57). The results are summarized in [Table 1].
|Table 1: Summary of evidence from systematic reviews on the cuff leak test|
Click here to view
As both meta-analyses were largely based on observational studies, there may be a large element of bias, leaving the accuracy of the CLT undetermined. In attempts to clarify the accuracy, the authors of the American Thoracic Society's Clinical Practice Guidelines on the Liberation from Mechanical Ventilation used the data from 14 observational trials to simulate a clinical trial. They assumed that those who failed the CLT had a delay in extubation by 1 day, and all patients in the control group as well as those who passed their CLT were extubated without delay. The results of the simulated trial showed that the cuff leak-guided management decreased postextubation stridor (risk ratio [RR], 0.6; 95% CI: 0.47–0.77) and ultimately reintubation rates (RR 0.58; 95% CI: 0.40–0.83). However, they also found that the CLT unnecessarily delayed extubations (9.2% absolute increase). This may be particularly concerning in those select patients who have a false-positive test (i.e., an absence of a cuff leak when no LE actually exists). Not only will a false-positive CLT delay extubation, but it may also expose patients unnecessarily to the treatment of LE, which is typically a course of systemic steroids. The very low quality of the body of evidence has led the guideline panel to issue a weak recommendation to perform CLT prior to extubating high-risk patients, leaving other populations without specific guidance. While they suggested that high-risk patients (i.e., those intubated for more than 6 days, had a traumatic intubation, have a large ETT tube, or were reintubated after an unplanned extubation) should have the test done prior to extubation, they stated that each patient should be assessed individually for their risk of LE. This is a clear reflection of paucity of evidence.
| Evidence Gaps and Future Direction|| |
There are no surveys in the literature that describe the behavior and beliefs of intensivists with regard to the CLT. Therefore, it is not possible to predict how large of a problem is this in clinical practice. As part of Cuff leak and airway Obstruction in Mechanically ventilated ICU patients (COMIC) research program, we have planned to conduct an international survey that will help to understand the variability in practice in Canada, Europe, and Saudi Arabia.
Given the fact that all prior studies are at a considerable risk of bias, the diagnostic accuracy of the CLT is still unknown. In addition, it is possible that the routine use of the CLT may potentially be harmful by prolonging mechanical ventilation, and subsequently, increasing the risks of barotrauma, ventilator-associated pneumonia, and ICU length of stay. Therefore, a large randomized clinical trial is necessary to investigate the diagnostic accuracy of the CLT and its impact on patients' outcomes. Herein, we are introducing the COMIC Trial. In the COMIC Trial, we will randomize adult critically ill ventilated patients who are deemed ready to be extubated into two groups. In the control group, the CLT will be performed but the results will not be communicated to the physician and the patient will be extubated regardless of the results. While in the intervention group, the physician will be notified of the results of the test. If the patient fails the CLT, the physician will be encouraged to provide the patient with a short course of steroids prior to extubation. Patient important outcomes such as rates of reintubation for upper airway obstruction, duration of mechanical ventilation, mortality, and ICU lengths of stay will be explored. This RCT will also allow us to capture the accuracy of the test and to determine the best method to measure the cuff leak.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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