Leakage around an endotracheal tube (ETT) is a common problem in the intensive care unit (ICU). Rashkin and Davis1 found 15 incidents of air leak among 61 patients whose lungs were mechanically ventilated for >3 days. Stauffer et al.2 observed an inability to obtain a proper airway seal in 11% of 226 intubations, while Zwillich et al.3 found an incidence of massive air leaks around the ETT cuff of 5.9%. ETT cuff leaks can also be encountered in the operating room.4 A wide range of consequences can result if the leak is not properly managed. These can vary from a mere annoying bubbling sound to a life-threatening respiratory compromise requiring immediate intervention.5 ETT replacement is usually performed in these situations, even though it may not be necessary; such decisions can expose the patient to airway loss or life-threatening hypoxemia during the ETT exchange.
We searched the literature from January 1980 through June 2012 using PubMed/MEDLINE, Cochrane collaboration library, and EMBASE database for the terms “endotracheal tube + cuff leak” and “airway + cuff leak.” Only few reports investigated the incidence of airway leaks and the relative contribution of cuff defects to the problem.1–3,5 Scattered conservative management ideas, mostly contained in letters to the editor, were also found. We could not find any randomized clinical trials addressing management options. There are no recommended guidelines on how to deal with an ETT cuff leak and no published step-by-step safe management strategy. The goal of this article is to highlight this common problem, discuss its causes, consequences, as well as previously proposed management ideas. It is to be noted that the review addresses unintentional cuff leaks, which should not be confused with intentional cuff deflation or the cuff-leak test. The latter is performed intentionally to test the safety of tracheal extubation after prolonged intubation, or in upper airway edema/obstruction situations. Finally, a simple management algorithm will also be suggested. This algorithm is not based on any hard evidence, since none is available, but follows general logical steps and safety rules and can be easily adopted by clinicians.
The causes of ETT cuff leaks can be broadly classified into 2 major categories: leaks around an intact cuff/inflation system and leaks due to a defective cuff and/or inflation system (Table 1):
Leaks Around an Intact Cuff/Inflation System
A bubbling sound is not always due to a cuff tear. In fact, the majority of leaks are not associated with any structural cuff defects. Kearl and Hooper5 examined 18 ETTs that were reported to exhibit massive air leaks and were subsequently replaced in mechanically ventilated patients in the ICU. The authors found that 11 of the ETTs were in fact intact. Leaks, despite an intact and properly functioning cuff and inflation system, can occur due to the following:
Incomplete initial cuff inflation or subsequent cuff deflation (due to nitrous oxide discontinuation after prolonged administration)6 can result in leakage around the ETT underinflated cuff. To obtain an adequate seal, it is recommended to inflate the cuff initially to a no-audible leak point at applied airway pressures of 20 cm H2O.7 It has been shown that the best way to ensure adequate sealing and avoid underinflation (or overinflation) is to monitor the intracuff pressure periodically and maintain the intracuff pressure within the safe 20 to 30 cm H2O range.8 This pressure range provides an adequate seal (to prevent backward leakage of tidal volume or forward leakage of fluids into the lungs) without interrupting tracheal mucosal blood flow. Many types of cuff pressure monitors are currently available. Some allow continuous monitoring with automatic adjustment to a preset pressure.9 A syringe sensitive to cuff pressure changes has also been described recently.10
Cephalad Migration of the ETT
Pharyngeal dislocation of the ETT (Fig. 1) is the most common cause of air leak in mechanically ventilated ICU patients.5,11,12 Events in the ICU environment that may predispose to this problem include repeated coughing, tongue movements, inadequate sedation, improper ETT fixation, secretions, frequent suctioning, head extension, accidental ETT pulling, and moving the patient to change bed sheets or clothing. Partial tracheal extubation may also occur in the operating room due to improper initial ETT positioning, improper fixation, excessive head extension, and during patient’s positioning or transport.13 Cephalad ETT migration can be diagnosed by checking the depth mark on the ETT, suprasternal cuff palpation,14 and auscultation of air entry. The stiff, preformed ETT may soften with prolonged ventilation in the ICU setting. Cephalad migration of the ETT tip may lead to bending of the soft ETT in the pharynx, especially when it is properly secured at the mouth.11 This results in partial extubation without changes in the external depth marker. Direct laryngoscopic or videolaryngoscopic examination may be needed to establish the diagnosis in this situation. If not feasible, or if other clinical signs are conflicting, the ETT position should be checked using a flexible bronchoscope (FB). In the critical care setting, a daily chest radiograph is recommended to confirm ETT position.15 Partial tracheal extubation is a preventable complication, and all available measures should be used to ensure that the ETT is at the proper depth at all times.
Inadvertent Intratracheal Placement of Gastric Tube
Ozer and Benumof16 studied the passage of oral and nasal gastric tubes (GTs) with a fiberscope introduced through the left naris. Tracheal misplacement of the GT occurred in 6 of 120 subjects (5%).16 GTs may pass alongside the cuff to reach the distal trachea and bronchi. Leakage through the lumen of the GT leads to a gradual decrease in the tidal volume. If suction is applied to the GT, all the delivered tidal volume may be suctioned, leading to failure of the ventilator bellows to refill on exhalation. Clamping the GT prevents the leak, restores the set tidal volume, and provides a diagnostic test.17 Radiologic confirmation of proper position is recommended, since using the tracheally misplaced GT for feeding can result in a severe or fatal pulmonary soiling.18
Discrepancy Between ETT and Tracheal Diameters
Ng and Bittner19 reported air leak in a patient with Mounier-Kuhn syndrome who had a dilated trachea. The leak was noted despite tracheal intubation with an 8.0-mm cuffed ETT, cuff inflation with a volume of 12 mL of air, and an intracuff pressure of 22 cm H2O. A computed tomographic image showed proper positioning of the ETT, proper cuff location, and a massively dilated trachea (31.5-mm diameter). Although the syndrome is rare, it illustrates the possibility that a leak can result from using a disproportionately small diameter ETT to ventilate the lungs of a normal-sized adult. In addition, the elastic properties of the proximal airway are frequently altered in patients with obstructive lung disease.20 The resulting changes in airway distensibility may result in a leak after tracheal intubation and cuff inflation.
High Mean Airway Pressure
Guyton et al.21 demonstrated that a higher intracuff pressure is required with high mean airway pressures to maintain the seal between the ETT cuff and the tracheal wall. Increasing the intracuff pressure above a certain limit (25 mm Hg, or 34 cm H2O), however, increases the risk of tracheal mucosal necrosis.22 In 1 study,5 a cuff pressure >25 mm Hg was required to maintain the seal when the mean airway pressure was >48 cm H2O (35 mm Hg). Higher airway pressures or lower ETT cuff pressures resulted in air leak around the ETT.
Leaks Due to a Defective Cuff and/or Inflation System
The 1-way cuff inflation valve can be the site of the leak.23 An incompetent valve may be due to a manufacturing defect or mechanical damage. Failure to retain the air inside the cuff results in a gradual decrease in cuff size and gradual increase in air leak. It has been recommended to leave the air syringe connected to the port after inflation to act as a relief valve and guard against cuff overinflation.24 However, this practice was found to also damage the valve system and is not advisable.25
Whether due to a manufacturing defect or accidental trauma by a needle or a sharp object, punctures or tears in the pilot balloon will lead to failure to achieve or sustain cuff inflation.26 If the tear is large, all injected air will escape before reaching the cuff and result in failure to inflate the cuff from the beginning. With smaller tears or punctures, the cuff may initially inflate, but gradual air seepage through the perforation will eventually result in total deflation of the ETT cuff.
In rare occasions, the defect lies in the inflation tubing between the pilot balloon and the ETT cuff. Gupta et al.27 reported a case wherein the inflation tube was damaged by the adhesive plaster used for tube fixation and resulted in a leaky cuff. In another case report, a manufacturing defect was found in the intratubal part of the inflation tubing.28 Here as well, the onset and magnitude of the leak will depend on the size of the defect.
A cuff defect is the most common structural cause of air leakage.5 Cuff incompetence may result from a manufacturing defect. Rho et al.29 reported a massive persistent air leak due to a manufacturing defect leading to an asymmetric cuff inflation. However, more often, cuff defects are caused by inadvertent trauma to the thin-walled cuff. Friction against sharp teeth during multiple introductions and withdrawals of the ETT at the time of tracheal intubation is frequently responsible.30 Spraying the cuff with local anesthetic sprays has also been found to cause cuff damage.31 Surgical-induced trauma (by a needle, scalpel, electrocautery, retractor) during neck surgery may also result in a cuff tear.32 Laser surgery of the upper airway may also tear, perforate, or burn the ETT cuff.33 It is important to always test cuff inflation before tracheal intubation to ensure its proper performance once the ETT is in place.
CONSEQUENCES OF AN ETT CUFF LEAK
The clinical consequences of an ETT cuff leak depend on the lost volume, patient characteristics, indication for ventilation and tracheal intubation, and type of surgery. These consequences range from an inconsequential noisy bubbling sound to a massive loss of tidal volume necessitating ETT replacement.5 Aspiration of gastric contents or pharyngeal secretions may also occur, since there is no proper isolation to protect the lungs.34 It can be either a full blown aspiration when the cuff is ruptured and fully deflated, or “microaspiration” that may occur when the cuff is underinflated or even when fully inflated.35 The problem is common with high-volume low-pressure ETT cuffs (the most commonly used ETTs). It has been reported that fluid leakage occurs through longitudinal folds that form in the cuff membrane even when it is fully inflated.36 Microaspiration is the major cause of ventilator-associated pneumonitis in mechanically ventilated ICU patients.37 ETTs with ultrathin polyurethane membrane have been recommended recently to reduce the incidence of microaspiration.38 Alternatively, an ETT with a low-pressure low-volume cuff can be used, since such cuffs may not develop longitudinal folds.39 Because the folds in the traditional high-volume low-pressure cuff allow fluid leakage, they may also allow minor retrograde gas leakage from the lungs, decreasing the effective tidal volume. Pollution with anesthetic gases is another problem that can occur if the anesthetic gas mixture leaks during surgery.4,40 In addition, the surgical patient may receive less than the desired anesthetic concentration, resulting in inadequate depth of anesthesia. If the leak is sufficiently large, the capnographic waveform may be distorted or absent.41 In thoracic surgery, failure of lung separation occurs if the bronchial cuff of a double-lumen tube is damaged.42 In upper airway laser surgery, an airway fire can result from the leaked oxygen-rich gas mixture.43 The most serious complications in mechanically ventilated ICU patients are hypoxemia, hypercarbia, and respiratory failure due to failure to deliver the required minute ventilation, especially if the patient is dependent on positive end-expiratory pressure or needs high mean airway pressure to achieve adequate oxygenation and/or ventilation.44
PREVIOUSLY SUGGESTED SOLUTIONS TO ETT CUFF LEAKS (LITERATURE REVIEW)
When the cuff has a structural defect, the definitive solution is to replace the ETT. This solution can be technically difficult, however, in a patient with a previously difficult airway (DA), may be risky in patients with increased intracranial pressure or coronary artery disease who cannot tolerate the stress of laryngoscopy and tracheal reintubation, or even life-threatening in patients who cannot tolerate a brief interruption of ventilation. In many occasions, the exchange is cumbersome or not feasible (for instance, in head-and-neck surgery, in patients in prone position, or in patients with traumatized and edematous airway).
Innovative conservative solutions to solve the cuff-leak problem without changing the ETT have been suggested. Pharyngeal packing with soft gauze has been used to limit the leaked volume.45 Although this technique can be effective in many surgical procedures, it has limitations. Inability to completely prevent the leak, risk of aspiration around an incompetent cuff, trauma to the pharyngeal mucosa, and failure to retrieve the pack before tracheal extubation are known disadvantages.45 Watson and Harris23 used a 3-way stopcock as a secondary valve to stop the leak if the 1-way inflation valve was found incompetent. It should be noted that some of the modern stopcocks have a shorter male end that may not adequately engage and activate the plunger of the pilot balloon inflation valve, and a proper stopcock should be sought. If a hole in the pilot balloon is suspected, cutting the pilot balloon from the cuff tubing and inserting a 22-gauge IV catheter into the tubing with a stopcock valve attached to the catheter’s end can stop the leak. Instead of using an angiocath, Sprung et al.46 used a valve and inflating line cut from a similar, nondefective ETT and connected them to the cut distal part of the defective ETT using a hypodermic needle as a joint. The same solution can also be used if the defect is in the inflation tubing (not in the pilot balloon) that will have to be cut distal to the leak site. Instead of using a stopcock attached to a catheter, Barrios and Vitale47 clamped the inflating tubing 2 cm distal to the cut level after air injection.
If the defect is in the cuff, none of the aforementioned remedies will stop the leak. In this situation, Boussard etal.48 recommended continuous air insufflation through the inflation tubing to maintain an adequate pressure (and seal) in the perforated cuff. The gas flow required to prevent the leak depends on the size of the perforation. In 1 study, no leakage was observed when the gas flow to the cuff, and the measured cuff pressure, were adjusted according to the caliber of the cuff hole.49 This method, however, is not effective in controlling leakage from large holes or cuts. Batra and Rajeev50 were able to maintain a proper cuff seal when they used an infusion pump to continuously infuse air to keep the cuff pressure at 20 cm H2O after detecting a cuff leak. Others used constant oxygen flow delivered by a rotameter flowmeter that is connected to the inflation line by a tubing and a 3-way stopcock.30 Schubert et al.51 achieved an adequate seal when they used a mixture of lidocaine jelly and normal saline to inflate the defective cuff. All these conservative measures are temporary and the likelihood of their success depends largely on the size of perforation. When these temporary remedies are resorted to, the clinician should also remember to keep the intracuff pressure within the safe permissible range to avoid compromising tracheal mucosal blood flow for extended periods of time.
Examination and Risk Stratification
A bubbling noise and/or other signs of tidal volume loss should always be investigated. The first step is assessing the patient’s oxygenation and the urgency of intervention, followed by a quick machine check to exclude equipment-related leaks. Examination of the ETT depth (lip or teeth mark), chest auscultation and direct laryngoscopy (DL) should be performed initially. DL is an important step, because the cause of leakage may be partial extubation or a tracheally misplaced GT. DL also helps to assess the laryngeal view and determine the likelihood of reintubation difficulty.
A thorough risk/benefit analysis should be performed in each case. Factors that should be considered in this analysis process include: (1) length of time the patient will likely require mechanical ventilation; (2) patient’s history of a DA or poor laryngeal visualization; (3) the leaked volume and its effect on patient’s mechanical ventilation; (4) aspiration risk; (5) tolerance to brief periods of ventilation interruption; (6) expected response to laryngoscopy and intubation; (7) cervical spine status and presence of hard neck collar or halo fixation; and (8) patient’s position (supine versus prone or rotated 180° from anesthesia workstation).5
The definitive solution is ETT replacement, but a hasty and unplanned decision to exchange the ETT may place the patient at risk of airway loss and major morbidity and mortality.
The Role of Conservative Measures
The conservative measures described above can be used in the acute surgical setting, particularly when unencumbered access to the airway is problematic. However, ETT replacement will most likely be needed if prolonged ventilation is planned,52 or if the temporizing measures fail to control the leak and interfere with adequate mechanical ventilation.
The Low-Risk ETT Exchange
If the operator is able to visualize the indwelling ETT in situ between the vocal cords and laryngoscopy can be performed without serious side effects, then controlled tracheal extubation and reintubation under direct visualization should be considered.
The High-Risk Exchange
If laryngeal visualization is difficult or there is a history of DA (from airway edema, cervical spine injury, etc.), a more conservative approach is recommended for exchanging the ETT with a failed cuff. It is important to stress that airway loss is an ever-present risk during such ETT exchange, and the risk of reintubation failure is particularly high and life-threatening in the patient who is ventilator-dependent or needs high levels of positive end-expiratory pressure. History, airway examination, and DL can provide adequate initial airway assessment. History of DA, airway edema, anatomical changes due to surgery, trauma, or upper airway pathology, airway access restrictions from hard collars or halo fixation, morbidly obese patients with massive head-and-neck edema, and patients with neck contractures are examples of an anticipated difficult exchange. The following techniques may be considered for the high-risk exchange:
The Use of ETT Introducers and Exchange Catheters
The exchange can be accomplished using an ETT introducer as an exchange conduit. The introducer is passed through the old ETT into the trachea, the old ETT is removed, then the new ETT is advanced over the in situ introducer. Desai and Fencl53 successfully used this technique in > 50 patients without difficulty. Airway exchange catheters (AECs) are hollow (as opposed to the solid ETT introducers). Thus, they are advantageous, since oxygen insufflation or jet ventilation can be provided during the exchange process.54 Lambotte et al.55 reported 3 cases in which the use of an AEC allowed fast and atraumatic exchange of damaged ETTs during critical intraoperative incidents such as oropharyngeal bleeding and head-and-neck surgery. A potential limitation of the AECs is that they are not as rigid as the solid exchange catheters, and are thus more likely to kink during ETT reinsertion.
The Role of Flexible and Rigid Bronchoscopy
The FB has also been used to safely exchange ETTs. After oral or nasal insertion, Rosenbaum et al.56 advanced the FB between the vocal cords and alongside the indwelling ETT. The ETT-loaded FB was then advanced alongside the old ETT until the tip was just above the carina. The failed ETT was then removed, and the new one advanced over the FB (Fig. 2). Benumof57 used the same technique but recommended also inserting an AEC through the existing (failed) ETT before advancing the loaded FB beside it. The AEC can be removed after verifying successful exchange with the FB-loaded ETT. Asai58 also used the same technique to exchange an ETT with a ruptured cuff in a patient with a DA. He used a laryngeal mask airway that was placed behind the existing tube as a conduit to pass the loaded FB58 and advance the ETT into the trachea. If the advancement of the ETT over the FB or AEC is prevented by a “hang-up” of its tip, a 90° counter-clockwise rotation of the tube may solve the problem.59 Alternatively, the use of the Parker Flex-Tip tube (Parker Medical, Highlands Ranch, CO) has been advocated in these situations. This ETT has a curved tip that prevents it from impinging on laryngeal structures.60
Andrews et al.61 and Sprung et al.62 successfully used the WuScope, a rigid bronchoscope (Achi Corp., Fremont, CA, and Asahi Optical CO., Pentax, Tokyo, Japan), for ETT exchange in patients with DA. The use of this scope allows passing a suction catheter (or an AEC) through the glottis under vision, then using it as a conduit for insertion of the new ETT after removing the old one under continuous visual control.
The Evolving Role of Videolaryngoscopy
The new videolaryngoscopic technology allows continuous glottic visualization during the entire exchange process and can be extremely valuable in these situations. The Pentax-AWS videolaryngoscope (Ambu, Glen Burnie, MD and Pentax, Tokyo, Japan), the Airtraq (King Systems, Noblesville, IN), and the GlideScope (Diagnostic Ultrasound Corporation, Bothell, WA) have been used successfully for this purpose.63–65 These devices allow airway evaluation before the exchange, confirmation of tracheal placement of the AEC, recognizing accidental catheter withdrawal on existing ETT removal, maneuvering the replacement ETT tip under vision in case there is a hang-up to advancement, observing and confirming reintubation with the new ETT, and acting as a back-up intubation technique in case the exchange process is not successful.66 It must be cautioned, however, that videolaryngoscopy is not a guarantee of success. In rare cases, glottic visualization is possible, but tracheal intubation may prove difficult or even impossible. Thus, the use of AECs or preloaded FBs should be considered before removal of the failed cuff ETT.
Airway loss (or failure to reestablish the airway after existing ETT removal) should immediately trigger the institution of the American Society of Anesthesiologists’ difficult airway algorithm.67
Other Important Considerations
Oxygen insufflation throughout the exchange process is recommended and can be provided by a nasal cannula when appropriate or through the AEC.53 An experienced assistant should be notified and be available before the exchange. A DA cart with alternative ventilation devices should also be available. Equipment and personnel to perform an emergency surgical airway, if deemed necessary, should be at the bedside.
Leak Management Algorithm
A general management plan in the form of an algorithm is proposed in Figure 3. This simple algorithm may help guide the safe management of leaky ETT cuffs. The algorithm is not supported by any hard evidence, since none is available, but follows logical steps and safety rules. It constitutes a general framework and suggests individual management decisions that should always be based on the particular clinical situation.
In summary, leakage around ETT cuffs is not always caused by a structural defect. Partial tracheal extubation is a common cause that can be prevented by frequent checking and ensuring proper ETT insertion depth. Management of cuff leaks should be based on a thorough risk/benefit analysis of each individual situation and tailored to the particular clinical scenario. The definitive solution is to replace the ETT, but conservative measures may be used as a temporary solution in certain clinical situations. ETT exchange is indicated with major ETT cuff structural defects, or when conservative measures fail. Anesthesiologists should be adequately prepared with equipment, plans, and personnel before performing a high-risk exchange, and should follow the American Society of Anesthesiologists’ difficult airway algorithm if the exchange fails or the airway is lost during the procedure.
Name: Mohammad El-Orbany, MD.
Contribution: This author helped write the manuscript.
Attestation: Mohammad El-Orbany approved the final manuscript.
Name: M. Ramez Salem, MD.
Contribution: This author helped write the manuscript.
Attestation: M. Ramez Salem approved the final manuscript.
This manuscript was handled by: Sorin J. Brull, MD, FCARCI (Hon).
The authors would like to thank George J. Crystal, PhD for his valuable assistance during the preparation of this manuscript.
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