ETT Exchange in the ICU

Thomas C. Mort, MD

Senior Anesthesiologist
Associate Director, Surgical ICU
Hartford Hospital
Associate Professor of Anesthesiology & Surgery
University of Connecticut School of Medicine
Farmington, Connecticut

Ann-Marie Surette, MD

Senior Anesthesiology Resident
University of Connecticut Training Program
Farmington, Connecticut

Over a 23-year period, the Hartford Hospital Department of Anesthesiology Airway Management Quality Improvement Database has collected experiences with ETT exchanges in critically ill ICU patients in this tertiary care hospital. Here, the authors take a look at the data and reach some conclusions.

Jonathan Benumof, writing about safety measures during endotracheal tube (ETT) exchange, stated that changing an ETT is a “simple concept but not a simple procedure.”^1,2 Surprisingly, since these words were published, airway exchange has been infrequently discussed and sparsely investigated in the literature. Only recently has original research regarding the safety, best practice methods, and complications of ETT exchange appeared in the anesthesia literature.^3-5

While the exchange procedure remains a simple concept, we now have a better appreciation for and understanding of its dangers. Advances in airway adjuncts have led to overall fewer life-threatening events; however, there still remain the real risks for esophageal intubation, multiple attempts, and loss of the airway.^3-5Despite the potential dangers of hypoxia and cardiopulmonary instability, replacing an ETT in the critically ill patient is frequently required for ETT malfunction, location change (ie, nasal to oral), or upsizing of the ETT. These complications remind us that airway exchange is not a simple procedure.⁶

Moreover, the clinical presentation of the patient requiring an ETT exchange is as varied as its remedy. This procedure may be requested for an elective clinical event, for example, bronchoscopy, that requires a larger-caliber ETT. More often, urgent and emergent clinical conditions that threaten patient safety may prompt a call to the airway team. A damaged pilot balloon assembly or cuff microperforation may lead to inadequate oxygenation/ventilation and expose the patient’s tracheobronchial tree to oropharyngeal flora and soilage. Emergent intervention may also be prompted by ETT kinking, luminal narrowing and obstruction, or damage from the patient biting leading to an ETT wall defect.⁶

With little supporting evidence other than consultant opinion, the 1993 American Society of Anesthesiologists’ (ASA) Guidelines for Management of the Difficult Airway recommended maintaining continuous access to the airway during the exchange procedure. Certainly, clinical situations exist that prohibit the clinician’s ability to maintain continuous airway access; luminal kinking or occlusion may be particularly troublesome, often requiring lifesaving removal or exchange under extreme circumstances.⁷

The double-lumen tracheal tube (DLT), for example, is a harbinger of narrowing and obstruction from secretions, biofilm, and debris due to its smaller lumens coupled with the patient population that may present to the ICU with an indwelling DLT (chest trauma, pulmonary hemorrhage, necrotizing pneumonia). It may be judicious to perform an aggressive and early transition back to a single-lumen ETT in the perioperative period. Similarly, a small-bore, nasally placed ETT with luminal narrowing from excessive biofilm, blood clots, or secretions may present a significantly high-risk situation. In certain situations, denying the ETT exchange in favor of gaining surgical airway access may be a safer and prudent alternative. Indeed, ETT exchange is a simple concept but harbors great danger.

A plethora of methods are available to assist the airway team in performing the ETT exchange.⁶ Management strategies can be customized to the patient’s particular clinical situation, coupled with the needs and skills of the airway team. They can be conveniently grouped by whether or not access to the airway is maintained during the exchange. Continuous airway maintenance is typically accomplished with an airway exchange catheter (AEC), of which there are many styles and sizes. Despite the ASA’s initial recommendation for maintaining continuous airway access, the 2003 and 2013 updated guidelines do not specifically mention ETT exchange nor reinforce its previous recommendation (except in the extubation of a difficult airway).⁸

The literature remains relatively devoid of large, evidence-based studies to support or refute the rationale for AEC utilization. However, maintaining continuous airway access with an AEC, essentially a “Seldinger” technique, is a commonsense, straightforward, and time-tested safety “bridge.” Table 1 offers various methods of exchanging an ETT. Note that maintaining continuous airway access can be used with many of these airway management strategies.^4-6

Table 1. Variety of Methods for ETT Exchange
Method/Location/ETT Type	Airway Exchange Catheter (AEC)	No AEC
Direct laryngoscopy (DL)	X	X
Video-assisted laryngoscopy (VAL)	X	X
FOB with 2nd ETT (alongside the 1st ETT)a	X	X
Combined FOB + VAL or DL	X	X
Nasal-to-orala	X	X
Oral-to-nasala	X	X
DLT ? SLT	X	X
In-situ tracheostomy	X	X
No laryngoscopy assistance	X
Surgical airway access (elective)
aAEC placed in existing ETT to maintain continuous access to the airway during the exchange procedure.

An alternative approach to using an AEC for continuous airway access would be passage of an ETT-loaded fiber-optic bronchoscope (FOB) into the trachea alongside the existing ETT. This is a viable approach for oral-to-oral, nasal-to-oral, or oral-to-nasal exchanges.^6,9,10 Equally, this intubation can be executed alongside the AEC. AEC placement within the existing ETT is followed by withdrawal of the existing “old” ETT above the glottis; thus the “extubated” airway remains accessible via the indwelling AEC. This can then be followed by laryngoscopic intubation alongside the AEC or passing an ETT-loaded FOB side-by-side to the AEC and into the trachea. If intubation is difficult, re-advancing the “old” ETT over the indwelling AEC may be performed to re-establish the airway. This is assuming the “old” ETT has an intact cuff; if not, it can be removed and a new ETT can be railroaded over the AEC. A “pre-exchange” laryngoscopic examination of the airway may allow the team to assess the glottic cross-sectional area to determine if it would be appropriate to advance, for example, the FOB-ETT assembly side-by-side while the AEC maintains access to the airway.⁵

Exchange procedures have changed over time with the availability of more sophisticated laryngoscopy techniques and equipment, as well as rescue methods in the event of difficulty or failure. In 1949, Dr. Robert Macintosh published his experience using a gum-elastic bougie (originally a urinary catheter) as an introducer to facilitate difficult intubation. Use of introducers, however, did not become widespread until the advent of the Eschmann tracheal tube introducer in the 1970s.^11,12 This device was unique from the straight gum-elastic bougie: longer length with a 35-degree curved tip (coudé) and a two-layer design that provided stiffness while maintaining flexibility. In 1987, Cook Critical Care manufactured the Mettro (Mizus endotracheal tube replacement obturator), designed specifically for ETT exchange. Its drawback, the solid core design, did not permit supplemental oxygen delivery.¹³

Soon after, Cook developed a family of hollow, semirigid devices, known as Airway Exchange Catheters. These introducers offered the ability to maintain continuous airway access with the additional opportunity for oxygen delivery.¹³Dr. Richard Cooper, a pioneer and an innovator of the airway catheter concept as well as video-assisted laryngoscopy (VAL), was an early advocate of the airway catheter for ventilation, extubation of the difficult airway, and ETT exchanges. In the early 1990s, he introduced the Endotracheal Tube Ventilation Catheter (ETVC, Cardiomed). Similar to the Cook AECs, a proximal connector allowed for the delivery of oxygen through insufflation or jet ventilation. Dr. Cooper published his experience with the ETVC in over 200 patients, maintaining airway access following extubation of the difficult airway patient and supporting reintubation efforts.¹⁴ He has applied the airway catheter concept to a variety of airway rescue or bridging techniques that serve as the basis for many current practice standards.

Many brands and types of AECs are available for clinical use. One of the most widely used, and the brand that is used in our institution, is the variety manufactured by Cook Critical Care. Various lengths and diameters of these products are available, ranging from 45 to 83 cm and 8 to 19 Fr in diameter. Oxygen delivery via the Cook AEC is typically by 1 of 3 methods: free-flow oxygen (1-4 L/min) via a Rapi-Fit Luer lock adapter; reservoir bag via a Rapi-Fit 15-mm adapter; or high-pressure jet ventilation via a Rapi-Fit Luer lock adapter.

Unfortunately, the relatively small luminal cross-sectional area of the AEC, even with the largest 19 Fr catheter, restricts oxygen delivery via a reservoir bag due to high resistance. Moreover, free flow, reservoir bag, and jet oxygen delivery must be coupled with proper egress of pressurized oxygen to avert barotrauma.^2,15-17Several disadvantages of attaching an oxygen source to the AEC include: oxygen delivery in any fashion is necessarily interrupted at certain points of the exchange; additional personnel are required to focus attention on the oxygen delivery process; any attachments applied to the proximal end of the AEC could potentiate AEC tip migration more distally or proximally; and the more steps introduced into the exchange process, the more complicated the procedure becomes.

Since its introduction, improvements and alterations to the AEC have taken place to allow practitioners additional options and optimization of the exchange. One modification is the Aintree Intubation Catheter (AIC), which was brought into clinical practice in 1997.¹³ The AIC, essentially a shorter version of the 19 Fr Cook AEC but designed with a larger internal luminal diameter, permits concomitant use with a small- to medium-caliber FOB. The internal diameter of 4.7 mm allows a well-lubricated AIC to slide over a small to medium bronchoscope and act as a “jacket.” It can then be delivered through the ETT with direct FOB visualization to the trachea. Following bronchoscope removal from the AIC, the existing ETT can be removed over the AIC, which acts as an AEC. A new ETT can then be advanced over the AIC. Placing the FOB through the AIC can aid in identifying proper trachea placement and depth. The drawback of this method is the potential for the AIC to migrate following ETT removal and manipulation, either too far distally past the carina or above the glottis. Moreover, this exchange method requires an excessive number of steps and oxygen delivery is limited during the extended exchange process. This method should be reserved for those critcally ill patients with acceptable cardiopulmonary reserve. The advantage of the excess AEC length as opposed to the shorter AIC is that the longer version allows control of the proximal AEC end when exchanging the ETT in or out.

A distinct advantage of the AIC is its ability to act as a jacket for small and medium AECs (11 Fr, 14 Fr). If the operator is forced to use a smaller-caliber AEC, for example for a kinked ETT or DLT to single-lumen tube (SLT) exchange, then the AIC conveniently fits over the two smaller adult AECs (11 Fr and 14 Fr). Placing this jacket will facilitate ETT exchange by increasing AEC diameter and rigidity. Decreasing the gap between the AEC and ETT will reduce AEC coiling and allow for easier advancement of the ETT, reducing the risk for bevel impingement on the glottis during exchange.

Outside of ETT exchange, the AIC is a handy adjunct to facilitate difficult intubation. Its combination with FOB allows intratracheal advancement via a supraglottic airway device (SAD) under direct visualization. Following SAD removal, a new ETT can be passed over the free-standing AIC, or reloading the FOB-ETT combination through the AIC can assist with tracheal intubation.^18,19

The Airway Exchange Database

The Hartford Hospital Department of Anesthesiology Airway Management Quality Improvement (QI) Database offers our experience with ETT exchanges in critically ill ICU patients in a tertiary care hospital. This data collection began in the early 1990s and continues to the present, representing an airway exchange collection over a 23-year period. Although subsets of patients have been statistically analyzed, to date the entire database has not. The large variety of methods employed by the airway team for exchange procedures is a testament to the diversity of our staff’s experience, skill set, and judgment, coupled with the plethora of patient care issues.

With over 2,200 cases spanning more than two decades, our database bears witness to the evolution of both airway equipment and exchange techniques. This article is based on the retrospective, uncontrolled, and nonrandomized review of trends and observations in ETT exchange, with the goal of educating providers and improving patient safety. Ongoing review and analysis of the database has afforded us valuable information that has encouraged changes in practice and equipment options. For example, in the mid-1990s, our department stocked medium-sized AECs from two competing manufacturers. Following just 49 AEC-assisted exchange cases using one brand, its lack of rigidity and floppy nature were found to be a considerable risk for coiling with ETT advancement, particularly with larger-bore ETTs. Such coiling led to a significant number of these cases having multiple intubation attempts and subsequent patient safety events, such as esophageal intubation, difficult ETT advancement, and hypoxia-induced bradycardia. The use of this brand was subsequently discontinued. Similarly, use of high-pressure jet oxygen delivery via the AEC has been curtailed at our institution due to the high risk for barotrauma.

The 1993 ASA Difficult Airway publication recommending continuous airway access may seem a bit obsolete in 2017, given the availability of indirect (video-assisted) laryngoscopy and the plethora of airway rescue devices.⁷ Should the airway team rethink the value of deploying an AEC given the current advancements in airway management? Perhaps the routine use of VAL alone for ETT exchange would minimize complications with equal or improved first-pass success rates?^3,20-23 While an intriguing idea, uniform VAL use is unlikely to be a panacea. Perhaps there are certain subsets of patients or patient characteristics that would warrant use of an AEC? Or perhaps their use should be reserved for the known or suspected difficult airway or particular difficult airway characteristics? To date, we have not answered such queries.

Certainly, the risk–benefit ratio is worth discussing. However, as will be presented later in this review, an exchange without an indwelling AEC may place the patient at increased risk for a variety of life-threatening consequences, such as airway loss, multiple attempts, esophageal intubation, and hypoxia-related complications such as cardiac arrest. On the other hand, AEC use carries the extremely low but potentially life-threatening risk for tracheobronchial tree injury from distal tip puncture, tissue laceration, or injuries related to application of high-pressure oxygen. Moreover, a smaller-caliber AEC could exit the ETT via the Murphy eye and lead to a difficult exchange, or could exit via an unappreciated defect in the ETT (patient biting) and lead to other trauma.^24-32

As previously mentioned, separating patients by difficult airway characteristics could shed light on whether AEC utilization is beneficial in all patients or just selected patient groups. Of note, many of the patients in our database who underwent ETT exchange using direct laryngoscopy (DL) alone did so based on the team’s assessment of the airway being “low risk.” The outcome of many of these “low risk” cases was disastrous when, following ETT removal, the unsupported perilaryngeal anatomy collapsed and reintubation proved difficult or impossible.

While there are no studies examining which patients will benefit most from useof an AEC, the ICU airway is, in our opinion, predictably unpredictable. Due to provider anticipation and concern, the recognized difficult airway patient typically receives more focused attention with careful planning of a primary strategy as well as secondary and tertiary backup plans. Conversely, the unrecognized difficult airway patient may face increased risk due to a relative lack of resources, less time spent in patient preparation, and a tendency for fewer team members to be present at the bedside.

Thus, a higher number of attempts resulting in airway-related complications and hemodynamic alterations may plague the “lower-risk” patient profile. One can argue that the majority (if not all) of ICU patients should be assumed to have a difficult or unpredictable airway until proven otherwise.

Our database, a retrospective review of airway exchange cases, offers many insights that are worthy of discussion. We have found that use of the AEC to maintain airway access in any capacity shows an improved safety report card (Table 2). While over three-fourths of all cases in the database involve AEC utilization, a sizable number of cases (n=505) do not. What is clear is that all non–AEC-assisted exchanges have a much lower first-pass success rate coupled with a commensurate rise in multiple attempts (3 or more). This, in turn, leads to a marked increase in airway and hemodynamic complications (Table 2, second column).

Table 2. Continuous Airway Access for ETT Exchange: AEC vs Non-AEC Use
	AECa (n=1,737)	All Non-AEC (n=505)	Non-AEC, Non-VAL (n=325)
First-attempt success	80.2%	63.9%	49.4%
3 or more attempts	6.0%	23.1%	30.6%
Desaturation <90%	9.2%	13.8%	18.1%
Desaturation <80%	8.0%	17.4%	22.6%
Esophageal intubation	2.7%	15.1%	20.4%
Surgical airway rescue	0.4%	3.3%	6.3%
Bradycardia	5.1%	13.3%	18.8%
Cardiac arrest	1.1%	6.1%	12.1%
Rescue device required	7.7%	17.4%	27.4%
a All cases using an AEC alone or assisted by laryngoscopy (DL or VAL).

Over time, use of DL alone as an exchange method has decreased while use of VAL (with or without AEC) has increased markedly since its introduction into our practice in 2006.³⁴ When analyzing non-AEC cases only, VAL utilization for these exchanges significantly decreases complication rates in each of the categories. When VAL cases are removed from the non-AEC case analysis (Table 2, third column), first-pass success rates decline to 49%, with a dramatic rise in both airway and hemodynamic complications.

The remaining patients in the non-AEC, non-VAL group consist of unassisted DL and FOB exchange attempts. DL is limited by its uniocular view, need for adequate oral cavity and submandibular space, and inability to see “around the corner” to visualize an anterior glottis. Additionally, inserting the ETT into the mouth and along the line of sight may further restrict the view of the glottis. Although FOB is an excellent airway adjunct, its use as a stand-alone method for the exchange procedure is limited due to difficulty maneuvering past the unsupported, collapsed orohypopharyngeal and periglottic tissues. A simple chin lift–jaw thrust maneuver may assist the operator but, in the authors’ opinion, it has limited success in the intubated ICU patient. DL is often helpful in opening the pathway for FOB advancement as well as affording dual visualization (laryngoscopic view plus FOB view). Advanced laryngoscopy combined with FOB is another method with great potential when faced with difficult airway characteristics.

Within the non-AEC exchange group, data for cases performed with unassisted DL or VAL are presented in Table 3. Overall, the incidence of complications in the VAL group is significantly lower than in the DL group. One-third of DL cases required one or more accessory rescue methods to secure the airway, as compared to only 1.7% of cases in the VAL group. In these DL cases, rescue methods included the use of bougie assistance (n=13), supraglottic devices (laryngeal mask, n=33; Combitube, n=3), FOB (n=8), VAL (n=2), and a surgical airway (n=12).

The majority of exchanges performed with VAL alone fell into 1 of 3 categories: The airway was assumed to be less risky and it was elected not to use an AEC; providers were unable to pass the AEC due to ETT kinking, luminal narrowing, or obstruction; or VAL was used as the rescue method itself.

Table 3. Outcomes of Non–AEC-Assisted Exchanges
	All DL (n=192)	DL Grade Ia (n=92)	DL Grade IIa (n=34)	VAL (n=180)
First-attempt success	51.6%	81.5%	41.2%	91.7%
3 or more attempts	32.8%	11.0%	35.3%	4.4%
Desaturation <90%	19.4%	14.3%	11.8%	1.1%
Desaturation <80%	25.7%	7.7%	29.4%	5.9%
Esophageal intubation	31.3%	5.6%	38.2%	1.1%
Surgical airway rescue	6.3%	–	11.8%	0.6%
Bradycardia	21.0%	6.7%	29.4%	1.7%
Cardiac arrest	11.1%	4.4%	20.6%	0.6%
Rescue device required	33.3%	7.6%	38.2%	1.7%
a Cormack-Lehane glottic view of intubated airway.

Although this comparison is not a randomized, controlled analysis of unassisted DL versus VAL ETT exchange, the trend is striking and heavily favors VAL-assisted exchange if use of an AEC is not possible or considered necessary. Of note, only 33% of “DL alone” cases with a Cormack-Lehane (intubated) grade 3/4 view had a successful first-pass attempt. The “DL only” group would have achieved a significantly worse complication rate if all those patients found to have a grade 3/4 view on DL exam had continued using DL for the exchange. However, this subgroup, as noted by its restricted or poor DL view, underwent a change in approach by the airway team to execute the ETT exchange. Seventy-nine percent of patients who underwent a pre-exchange DL exam rendering a grade 3/4 view underwent a VAL-assisted exchange due to the airway team’s concern. Management issues and complications were present at alarmingly high rates in DL-alone exchanges, even in patients with a grade 1/2 view (Table 3). Assessing the patient pre-exchange and determining that their risk is low could reassure the airway team, leading to a pacified exchange approach.⁵ Letting one’s guard down could lead to significant safety concerns and patient injury. Table 3 presents disturbing results from non–AEC-assisted exchanges based on DL (alone) or VAL (alone) strategies.

Since the initiation of our database over 20 years ago, we have seen the evolution of airway management techniques and the increased availability of advanced airway devices. Provider judgment, past experience, available equipment, and the patient’s airway characteristics influence a practitioner’s approach to the planning and execution of the exchange.

The majority of our exchange cases (77.5%) were performed using continuous airway access. This overall rate of AEC use is impressive when it is compared with other reasonable and warranted patient safety recommendations offered by the ASA Difficult Airway Guidelines—for example, use of FOB. Although employing an AEC is recommended in most cases, certain clinical conditions (luminal narrowing, occlusion, or kinking) often preclude successful passage of the AEC. Complete ETT occlusion with the inability to ventilate or oxygenate will necessitate rapid removal of the ETT as a lifesaving intervention. A suspected ETT wall defect (patient biting) may allow for AEC passage; however, caution should be taken due to the risk for placing it through the defect and subsequent patient injury or airway loss.^24-33

Others found that the smaller-caliber 11 Fr AEC, particularly with a larger-bore ETT, might pass through the Murphy eye and cause exchange difficulties.^29,33Downsizing the AEC diameter to accommodate a smaller ETT, DLT, or an airway with luminal impingement is a simple task. However, the risks of passing a much larger ETT over a smaller AEC, as we will illustrate, are important to consider.

A variety of AEC sizes exist, and they should be stocked accordingly while ensuring their immediate availability at the point of care, such as the operating room, ICU, and PACU. Easy accessibility is a simple step to prevent one of the obstacles to AEC use. In our 1,656 cases documented to have employed AEC assistance, there were 89 exchanges (5.4%) where practitioners were unable to pass an AEC due to ETT kinking, luminal narrowing/blockage, or inappropriate AEC size. Personal preference not to use an AEC, perception of a low-risk airway,and presence of few to no difficult airway characteristics may influence AEC use. Table 4 lists a variety of possible factors in not employing an AEC to maintain continuous airway access.

Table 4. Contributing Factors: ETT Exchange Without an AEC

Personal practice habits

Complete ETT occlusion necessitating urgent extubation

Underestimation of difficult airway characteristics

Lack of equipment at the bedside

Limited stocking/restocking of AEC devices in the difficult airway cart

AEC attempted but unable to pass via ETT (kinking, occlusion, incorrect AEC size)

Unwillingness to retrieve properly sized AEC if desired size is not present in cart

Indolent or sluggish attitude toward airway safety

Inexperience or limited knowledge base regarding exchange procedure

Relative lack of evidence-based research touting the attributes of AEC-assisted ETT exchange

Unfamiliarity with the original 1993 ASA recommendation to maintain continuous airway access

Pre-Exchange Laryngoscopy

The value of laryngoscopy as a pre-exchange examination cannot be underestimated. Adjunct laryngoscopy facilitates removal and insertion of the ETT over an AEC. Moreover, it may improve visualization of periglottic anatomy and uncover potential problems during the exchange, such as partial or complete tracheal extubation presenting as a cuff leak.^5,35 Dr. Benumof, in his 1999 editorial in Anesthesiology, rightly points out that “the risk of failure to pass an ETT over an AEC can be minimized greatly if a laryngoscope is used concomitantly whenever possible.”¹ In addition, “Optimal laryngoscopy will help to clear the supraglottic pathway the ETT must take over the AEC and may allow the endoscopist to visualize or understand where resistance is being encountered and how to address it.”¹

While there are no studies that compare AEC-assisted exchange with and without laryngoscopy, our hospital database again offers observations and trends that suggest a significant advantage in using adjunct laryngoscopy. Table 5 compares AEC-assisted ETT exchange with and without laryngoscopy (DL or VAL), suggesting increased airway management difficulties and serious patient safety events in AEC-only exchanges. Both laryngoscopy and the AECs have limitations when used alone; however, these techniques likely reduce patient morbidity in combination.

Table 5. AEC-Assisted ETT Exchange: AEC Only vs Laryngoscopy + AEC
	AEC Only (n=137)	DL + AEC (n=733)	VAL + AEC (n=766)
First-attempt success	58.7%	75.3%	91.8%
3 or more attempts	11.6%	8.3%	2.3%
Desaturation <90%	21.9%	12%	3.9%
Desaturation <80%	21.9%	11.2%	2.1%
Esophageal intubation	8.0%	4.6%	0
Surgical airway rescue	2.2%	0.5%	0
Bradycardia	11.7%	8.0%	0.5%
Cardiac arrest	6.6%	1.6%	0
Rescue device required	13.1%	7.4%	4.3%

In the same article, Dr. Benumof asserted that failure of the ETT to pass the laryngeal inlet is typically from the tip engaging the right vocal cord or arytenoid.¹If resistance is met, slight ETT withdrawal (1-2 cm) followed by ETT rotation and advancement may overcome the resistance. He has recommended a 90-degree counterclockwise rotation of the ETT to ease advancement. Clockwise rotation may also be beneficial as well as an ETT “spinning” maneuver during advancement over the AEC (authors’ opinion).

Overall, improved periglottic visualization during an ETT exchange allows the practitioner to observe why and how to apply such maneuvers to improve efficiency and success of the reintubation process. Further, periglotticvisualization affords the ability to continuously observe the depth of the AEC (centimeter markings on outside wall), thus lowering the risk for either excessive distal advancement or proximal migration out of the trachea.^36,37

Finally, the pre-exchange laryngoscopy allows the team to assess the airway and aids in planning a strategy for ETT exchange. Important information can be gathered about the patient, such as the presence of a small mouth, large tongue, restrictions from a rigid cervical collar, glottic edema, and secretions. These airway findings will assist in developing both a primary and backup strategies for exchange. Pre-exchange laryngoscopy may also help determine if a surgical airway is a necessary alternative.⁵

The landscape of laryngoscopy, however, has changed considerably since Dr. Benumof’s recommendations. Once the only option, DL is often hampered by a restricted line of sight and inability to see “around the corner.” Moreover, the DL view obtained with an intubated airway is significantly more limited than the native airway. A DL-only airway assessment and exchange may proceed blindly and is associated with multiple attempts and increased risk for patient injury (Table 3).

Airway visualization may be improved with FOB, especially if combined with laryngoscopy. As mentioned previously, adjunct laryngoscopy may enhance the maneuverability of the bronchoscope and improve viewing by opening the supraglottic pathway. While FOB has been touted as a primary option for management of the known or presumed difficult airway, many anesthesia practitioners have not mastered or maintained bronchoscopic competency. It is the authors’ opinion that since the introduction of VAL and its ubiquitous use, many anesthesia providers do not incorporate fiber-optic skills into their routine practice. This may jeopardize patient care if FOB is truly the only viable alternative for management of an airway dilemma and the practitioner’s skills have decayed.

VAL has transformed the exchange procedure by improving periglotticvisualization in patients with limited DL exams.^3,5 As we know, enhancing visualization during the pre-exchange airway assessment is of paramount importance since it provides a wealth of information for planning and executing the exchange. For example, uncovering unrecognized partial or complete tracheal extubation is potentially lifesaving (Figure 3). Moreover, periglotticviewing during the exchange procedure offers a significant advantage. VAL allows relatively easy visualization of the AEC advancing through the indwelling ETT, confirms its position following ETT removal, and affords confirmation of tracheal reintubation in the vast majority of encounters.

A few words regarding positioning of the patient for the exchange procedure: The exchange is equivalent to tracheal intubation; thus, the same principles of fundamental positioning and optimizing the 3 airway axes are essential for either procedure. Both an AEC- and non–AEC-assisted exchange would likely benefit from optimizing the 3 airway axes. Adequate sniff position, neck extension or ramping/reverse Trendelenberg/HELP (head elevated laryngeal position)/elevated head of bed for the obese patient will likely improve intubation conditions, even if VAL is incorporated. Similarly, optimizing positioning of the 3 airway axes in an AEC-assisted exchange may ease the removal and passing of the ETT due to the less acute, more relaxed angle the AEC takes from the mouth to the trachea. Why? In a patient with restricted neck motion, for example, wearing a hard cervical collar, the indwelling AEC takes a nearly 80- to 90-degree angle from the oral cavity to the hypopharynx, which is followed by a gentle upward incline from the posterior pharyngeal wall up to the glottis opening, rather than a straighter line into the trachea. Conversely, positioning with neck extension, sniffing position, ramping, etc, can soften the angle of approach and ETT advancement distally. These principles of positioning are particularly applicable when using a smaller-caliber AEC and a large ETT. Moreover, sufficient lubrication is imperative for smooth ETT movement. If time is available, warming the new ETT will soften its thermolabile character and improve its navigation over the AEC.

A recently published study of ETT exchanges in the ICU compared a historical group of difficult airway patients managed with DL + AEC and a similarly difficult group managed with VAL + AEC. The historical control group (n=337) was composed of patients who were classified as having poor view with DL during pre-exchange airway assessment (Cormack-Lehane grades 3 and 4) and underwent a DL + AEC–assisted exchange. The study group (n=328) consisted of patients who underwent an initial DL exam that also disclosed a grade 3 or 4 view; they were then assessed with VAL and ETT exchange was completed with VAL + AEC.⁵

The researchers hypothesized that VAL, when compared with DL, would improve glottic viewing for airway assessment. Moreover, they postulated that VAL + AEC exchange would result in a reduction in airway and hemodynamic complications when compared with the historical group of DL + AEC exchange. The number of attempts, complications, and rescue devices required for ETT exchange were analyzed in the two groups.⁵

In the VAL group, the majority of patients (88%) had a “full or near-full view” despite having a poor view (grade 3 and 4) with DL. First-pass success rate for ETT exchange differed significantly between the two groups (91.5% for VAL + AEC vs 67.7% for DL + AEC), and the number of patients requiring 3 or more attempts was statistically lower in the VAL group (1.2% for VAL + AEC vs 6.8% for DL + AEC). The incidence of mild and severe hypoxemia, esophageal intubation, bradycardia, and need for a rescue airway device were also statistically reduced in the VAL + AEC group.⁵

It was concluded that adjunct VAL results in far better glottic viewing for pre-exchange airway assessment. The improved periglottic visualization resulted in fewer airway and hemodynamic complications by affording timely ETT passage with enhanced first-pass success.^3,5 Thus, VAL + AEC–assisted ETT exchange is consistent with the recommendation of the ASA Difficult Airway Task Force to limit the number of laryngoscopic attempts during endotracheal intubation.

Partial and Complete Tracheal Extubation Masquerading as a Cuff Leak

An interesting and unexpected clinical finding in the above study was the substantial number of cases (n=171) of proximal ETT migration that wereuncovered during the pre-exchange VAL airway assessment.^5,35 In these cases, the airway team was called to the bedside to evaluate a “cuff leak” and perform ETT exchange. Again, the pre-exchange airway assessment provided valuable information, allowing the anesthesia team to diagnose proximal ETT migration with the cuff and/or tip at or above the glottis. This valuable clinical information could prevent an unsuspecting practitioner from advancing an AEC via the proximally displaced ETT, potentially leading to catastrophic patient injury. When the request for exchange is due to a “cuff leak,” it is imperative that the etiology to explain the cuff leak is known prior to the exchange (Figures 3 and 4).

Assessment of ETT position can be performed by VAL or FOB. The advantage of FOB is that a completely extubated trachea with the ETT tip positioned above the glottis can be reintubated via FOB guidance. Recognition of this ETT displacement via VAL usually requires incorporating a new styletted ETT for replacement of the softened, thermolabile, displaced ETT that may be difficult to advance forward (lacking a stylet).

The University of Michigan recently published its institution’s experience with ETT exchanges. This study provided valuable new insight into the risks of the Cook AEC.⁴ In over 500 ETT exchanges using this AEC, the overall failure rate (defined as the inability to complete the ETT exchange as intended) was significantly high at 13.8%. In comparison, the overall failure rate in our QI database is 9.9%. These failures varied depending on the type of ETT exchange: 0% for DLT to SLT, 9.3% for SLT to SLT, and 39.9% for SLT to DLT. This study also reported a 7.8% airway injury rate using AECs for ETT exchange. The majority of the institution’s pneumothorax cases (1.5%; 8/527) were associated with a difficult primary intubation or exchange.⁴

Interestingly, the authors commented that they had inadequate data to make conclusions about a relationship between Cook AEC size and exchange failure or patient injury. Dr. McLean and her team also did not report specific details about the exchange method used—that is, what technique was used or whether adjunct laryngoscopy was employed. They also did not report on individual complications related to airway or hemodynamic alterations. Finally, they only included patients who had undergone “general anesthesia” and did not comment specifically on the location of the exchange procedure. Their analysis likely reviewed mostly operating-room cases under elective, controlled circumstances.

The Influence of AEC Diameter

The size of the AEC, as well as the corresponding ETT size, are significant factors contributing to reintubation difficulty or failure. The AEC-assisted ETT exchange is essentially the airway team applying the Seldinger technique to the airway, similar to the obturator and a close-fitting wire in a central line kit. Minimizing the gap allows smooth advancement of the obturator over the wire. The AEC’s diameter directly influences its pliability or relative stiffness. A thinner, more pliable AEC, when paired with a large-diameter ETT, leads to a significant gap (eg, 11 Fr AEC/3.7 mm external diameter with an 8.0 mm ETT). This size discrepancy contributes to AEC coiling or buckling when attempting to advance the ETT.

Moreover, a significant size gap between the AEC and ETT creates ETT wobble during its advancement. This predisposes the free edge of the ETT’s beveled tip to meet resistance by abutting the vocal cords and arytenoids, particularly on the right side of the glottis. Overall, minimizing the gap between the AEC and ETT allows for smoother ETT advancement. This principle can also be applied to ETT advancement over a bronchoscope or bougie catheter.^1,2 If exchanging a DLT for a SLT-ETT, one interesting option when using the 11 Fr AEC would be to remove the DLT over two 11 Fr AECs. Reintubation over the two smaller AECs as a single unit is likely to be more efficient and timely.³⁰

This simple principle of “minimizing the gap” was championed by Dr. Benumof in the middle to late 1990s. Referencing again his 1999 editorial, he espoused the advantage of a narrower gap to improve the Seldinger-based exchange efficiency and first-pass success.¹ In his words, “the risk that an ETT will fail to pass the laryngeal inlet is minimized when a relatively small ETT and a relatively large AEC are used.” Concurrently, Dr. Benumof emphasized the importance of allowing a gap to afford better egress of pressurized oxygen if jet ventilation is used.¹ The airway team must weigh the benefits versus risks of either choice. A smaller 11 Fr or 14 Fr AEC with a larger-bore 8.0-mm ETT may provide pressurization relief while “jetting,” but the exchange itself may be compromised by the widened gap. Further to consider is the actual rate of implementing oxygen supplementation via the AEC. This remains an unknown quantity.¹⁵

As previously mentioned, and in light of the excellent results combining VAL and AEC (minimizing the gap between the ETT and AEC), our anesthesia department has almost completely abandoned using high-pressure oxygen delivery via the AEC in these clinical cases due to the potential for patient injury. Thus, we would favor minimizing the gap between the AEC and ETT as a much more adaptable alternative. Moreover, complementing the exchange with laryngoscopy, preferring the method that offers the best periglottic visualization is imperative to optimizing patient safety.^3,5

The Hartford Hospital QI database also supports narrowing the gap to improve the timeliness and efficacy of ETT exchange. In the “AEC only” exchange subgroup (n=137), diameter size was inversely associated with complications and number of attempts. Overall, the first-pass success rate in this subgroup was 58.7% (Table 5). A more detailed breakdown of these cases illustrates the importance of diameter to exchange success. For 11 Fr, 14 Fr, and 19 Fr AEC-assisted exchanges without the benefit of laryngoscopy, the first-pass success rates were 14.3%, 53%, and 75%, respectively.

Table 6. Cross-Sectional Areaa of Commonly Used AECs and ETTs
AEC	11 Fr 10 mm2
	14 Fr 17 mm2
	19 Fr 31 mm2
ETT	6.0 mm ID 28 mm2
	6.5 mm ID 33 mm2
	7.0 mm ID 39 mm2
	7.5 mm ID 44 mm2
	8.0 mm ID 50 mm2
	9.0 mm ID 64 mm2
aApproximate value rounded up

Table 6 presents the internal diameter (ID) for some common ETT sizes and the outer diameter (OD) of the 3 adult AEC sizes used at our institution. The cross-sectional area of the ETT lumen compared with the OD of the AEC is dramatic when one compares the 11 Fr (10 mm²) AEC providing support for an 8.0 mm ETT (50 mm²). So it is not surprising that the smaller-caliber AEC is associated with more difficulty and a higher complication rate. Conversely, the 19 Fr AEC (31 mm²) provides efficient and smooth support for the 7.0, 7.5, and 8.0 mm ETT (assuming adequate lubrication). Reviewing the gap relationship and the capacity of the ETT lumen in Figures 5-7 with the cross-sectional areas in Table 6, it is much easier to understand the vast difference in the gap for the various combinations used in clinical practice. The recent rise in popularity of the subglottic suction-capable ETT has introduced another potential factor to consider during ETT exchange and the choice of AEC. With the added function of subglottic suction, the OD is widened. As an example, the standard 8.0 mm ID has an OD of 10.8 to 11.0 mm compared with 11.8 to 12.0 mm for the newer specialty ETT. Therefore, its OD is equivalent to a standard 9.0 mm ETT OD. The increased thickness of the ETT wall (OD/ID ratio) leads to a more rigid composition. Combining the increase in size and rigidity of the specialty ETT, these two factors may present more difficulty during the exchange procedure when paired with a smaller-caliber AEC. Likewise, these trends in improved patient safety continue when adjunct laryngoscopy supplements the AEC-assisted exchange.

An alternative to the more flexible 11 Fr and 14 Fr AECs is available from Cook that combines a more rigid construction of the catheter itself with a softened distal tip. These improvements are welcome but vigilance must remain with appreciation of the tip location.³⁹ A direct comparison of the OD of the AEC with the ID of various ETT sizes is useful to more fully appreciate the different combinations that match an AEC to an ETT (Table 6).

When comparing all patients who underwent an AEC-assisted exchange, regardless of DL or VAL use, complications and number of attempts appear to be influenced by AEC size (larger-diameter AEC associated with fewer complications and attempts). Further, within the subgroup of patients who underwent adjunct laryngoscopy with DL or VAL, there is a clear trend that AEC size influenced complication rates and efficiency of the exchange. The smaller-caliber AEC is less rigid than its larger cousins, and tends to be more flexible and prone to coiling when a stiff ETT is railroaded over it.

Cases based on the laryngoscope method and documented AEC size are presented in Table 7 and Figures 13-15. Several points appear obvious:

1. First-pass success is correlated with AEC size (larger diameter, higher success rate), regardless of the laryngoscopy method.
2. Airway and hemodynamic complications decrease with a larger-diameter AEC.
3. The majority of complications and exchange inefficiencies are related to the smaller 11 Fr AEC.
4. VAL improves first-pass success, affords fewer attempts, and reduces complications, even when using the smaller 11 Fr AEC.
5. Adjunct VAL is overall far superior to DL when performing AEC-assistedexchange, particularly with the 11 Fr and 14 Fr AEC.

Table 7. All AEC Exchanges by AEC Size and Laryngoscopy Methoda
	DL-11 Fr (n=137)	DL-14 Fr (n=240)	DL-19 Fr (n=310)	VAL-11 Fr (n=80)	VAL-14 Fr (n=237)	VAL-19 Fr (n=262)
First-attempt success	40.9%	78.3%	87.7%	71.3%	86.5%	98.5%
3 or more attempts	32.1%	3.8%	1.6%	10%	3.8%	0
Desaturation <90%	32.1%	9.6%	9.6%	6.3%	6.5%	3.1%
Desaturation <80%	23.4%	9.6%	7.4%	5%	3.4%	0.8%
Esophageal intubation	16.8%	2.1%	1.9%	0	0	0
Surgical airway rescue	2.9%	0	0	0	0	0
Bradycardia	18.2%	4.6%	6.8%	3.8%	0.4%	0
Cardiac arrest	5.1%	0.4%	1.2%	0	0	0
Rescue device required	22.6%	3.7%	4.5%	0	0.8%	0.8%
a AEC size was documented in 84.5% of cases where AEC was used.

 

It is also essential to educate members of the anesthesia team about the risks of AECs. Pundits have discouraged AEC use due to its potential life-threatening complications, stating that the risks may outweigh the benefits. Some providers have even questioned their use at all, stating that a safer alternative needs to be found.³⁸ Case reports have illustrated specific drawbacks of the AEC, such as tracheobronchial trauma complicated by barotrauma, pneumothorax (PTX), tension pneumothorax (TPTX), and mucosal laceration or wall perforation.^24-33

These adverse events are typically caused by two preventable factors: excessive distal AEC advancement and oxygen delivery (typically pressurized) via the AEC. Without question, these AEC-induced consequences are catastrophic, but the exact incidence of such mishaps is unknown and is likely very low. Also, while it is easy to place the blame on the AEC, it is the operator who is responsible for distal tip migration or the application of pressurized oxygen.

To prevent the former, one provider should be assigned to maintain proper positioning of the AEC. At the same time, it remains a team effort to closely monitor the AEC depth during the entire exchange procedure. As highlighted in the literature, patient injury and loss of the airway may also occur from misplacement of the AEC. In a case report, practitioners inadvertently threaded an AEC through an ETT defect that was caused by patient biting.³³ In a second case report, Nates found that the smaller 11 F AEC may traverse the ETT Murphy eye, leading to obvious exchange difficulties.²⁹ Laryngeal or vocal cord trauma can also result from difficulty passing the new ETT over the AEC. Again, periglottic visualization provides valuable feedback for observing appropriate distal AEC advancement as well as proximal migration out of the trachea.5

As previously discussed, the risk for barotrauma from oxygen delivery via the AEC can be mitigated by allowing proper egress of the gas. Application of an oxygen source on the proximal end of the AEC can also lead to distal or proximal catheter migration. Interrupting oxygen delivery is necessary to remove or place the ETT on the AEC and requires reapplying the available adapter. Each additional step adds time to the process and increases the difficulty of the exchange.

An alternative approach for the delivery of supplemental oxygen would be passing the AEC via an enclosed system (ETT with a bronchoscopic Bodai adapter, Sontek Medical) with an attached oxygen reservoir bag. Again, this is a useful adjunct, but the author (TCM) has found it to be cumbersome unless practiced and rehearsed. It is, however, a viable low-pressure oxygen delivery method that requires the least number of steps compared with the other oxygen delivery methods.

Published data reporting the incidence of barotrauma or tracheobronchial wall perforation is sparse, but this complication can be catastophic.31,32 McLean’s group reported an overall PTX rate of 1.5% (8/527) with AEC use for ETT exchange, citing difficult intubations or exchanges in 6 of the patients.4 They also found a 4.1% risk for PTX in the patients with a failed exchange.4 While this complication rate was not statistically significant compared with successful AEC-assisted exchanges, the overall number of cases was low and possibly limited this comparison. They were also unable to determine the relationship between catheter characteristics (such as type and size of the Cook AEC) and incidence of PTX.

The Hartford Hospital database had a total of 24 cases of PTX over a period of 23 years (1.1%). Detailed analysis of these cases revealed that PTX was more likely with the following patient characteristics and clinical situations:

• patients undergoing massive resuscitation
• ventilator with PEEP ≥10
• trauma patients
• double-lumen ETT in place
• high-pressure jet oxygen delivery via the AEC.

Seven of the 24 PTX cases were preexisting and asymptomatic on pre-exchange radiographic studies. Of note, 9 of the 24 PTX cases had the ETT exchange completed without an AEC (inability to advance through the ETT) but were considered difficult intubations. A total of 6 cases of life-threatening cardiovascular collapse (2 PTX, 4 TPTX) were thought to be caused by high-pressure jet ventilation. Direct AEC tip trauma to the tracheobronchial tree was thought to contribute directly to 3 cases, 2 of which were TPTX. Overall, the incidence of serious injury from direct AEC tip trauma was only 0.17% (3/1,737).

Although these are serious consequences, the AEC has demonstrated an excellent track record of maintaining continuous airway access without complication in the vast majority of patients. Conversely, we have shown that there is an increase in patient morbidity and life-threatening consequences when exchange is attempted without an AEC.

Simple steps can be taken to minimize the risks associated with AEC use. Appreciation of the AEC tip depth (optimal being mid-tracheal), hence its visible black markings on the outside wall, is imperative not only during its initial advancement but throughout the entire exchange procedure (Figure 17). Thus, one person should be assigned to maintain its proper depth throughout the ETT exchange. The exchange is a team event and should be executed following a brief assignment of tasks to be completed by individuals at the bedside (laryngoscopist, AEC holder, ETT remover/advancer, etc).

Following the pre-exchange laryngoscopy to evaluate both the airway and ETT position, a lubricated AEC can be advanced via the indwelling ETT with the goal of matching the depth of the AEC to the depth of the ETT. Distinct black depth markings on the AEC can easily be matched to those on the ETT.

If positive-pressure or jet ventilation is administered through the AEC, extreme vigilance must be exercised. The provider should only use as much pressure as needed to obtain minimal satisfactory tidal volumes as assessed by chest movement. Additionally, a low respiratory rate (6-8 breaths per minute) is an absolute requisite to allow for a prolonged expiratory phase and egress of pressure. Expiration may also be improved by using a chin lift–jaw thrust, head extension, and possibly an oral airway.

Again, our anesthesia intensivists no longer incorporate and do not recommend using high-pressure jet ventilation via an AEC due to the high risk for barotrauma. The rationale is that its use by even highly experienced personnel has led to serious complications, hence we cannot support its use by less experienced airway colleagues.

Finally, misplacement of the AEC and trauma to the oropharynx or vocal cords can be minimized with use of DL or VAL to improve ETT passage and periglotticvisualization. Significant and life-threatening complications may occur, but these outcomes fortunately are uncommon if the AEC is managed appropriately.

In conclusion, the airway management of ICU patients requires advanced planning with a thorough evaluation of the patient and clinical situation. Vigilance in understanding the exchange procedure’s indications and weighing the risks versus benefits is of paramount importance. Unless truly urgent or emergent in nature—for example, complete luminal occlusion—a thorough pre-exchange airway evaluation should be performed to not only assist in planning the exchange strategy but potentially to uncover unrecognized life-threatening airway maladies. Occasionally, the exchange request may be denied in a high-risk patient where the choice of a surgical airway is more appropriate. When the decision is made to proceed with ETT exchange, a team approach to this procedure has distinct advantages regarding patient preparation and proper positioning, as well as implementing a strategy for both the procedure and backup methods for airway rescue.

A number of important insights to help readers minimize the risk of ETT exchange in critically ill patients are presented. These recommendations are based on the available literature, quality improvement projects, fundamental airway management principles, and a tincture of subjective opinion and experience.

ETT Exchange Recommendations

1. ETT exchange, particularly in the critically ill ICU patient, carries significant risk and the difficult airway is unpredictable.
2. ETT exchange is best managed by an experienced airway team, each person with a predetermined role.
3. A variety of methods and techniques exist to assist with ETT exchange, most of which can be used with an AEC.
4. A pre-exchange airway assessment is valuable for developing a plan and disclosing unrecognized airway problems, such as a cuff leak from partial or complete tracheal extubation.
5. Maintaining continuous airway access with an AEC is recommended and improves first-pass success rates with lower airway and hemodynamic complications.
6. Laryngoscopy, in any form, improves exchange efficiency and reduces complications by opening a pathway for ETT advancement and allowing visualization of potential problems.
7. Periglottic visualization with VAL further improves first-pass success and reduces airway and hemodynamic complications, especially in patients with Cormack-Lehane grade 3 and 4 views on DL assessment.
8. Minimizing the gap between the ETT and the AEC improves ETT exchange efficiency and reduces complications (Mind the Gap; Watch the Gap).
9. Exchange inefficiency and complications appear inversely related to AEC diameter, with the large AEC (19 Fr) sporting the best safety record, particularly when paired with laryngoscopy.
10. VAL improves first-pass success and reduces complications when using the smaller 11 Fr AEC.
11. Overall risk for tracheobronchial wall injury with AEC use is low and can be minimized by avoiding high-pressure jet ventilation and excessive distal placement of the AEC tip.
12. AEC use can be increased with practitioner education as well as ensuring that all AEC varieties are immediately available at the point of care.
13. Denying the request for an exchange or pursuing a surgical airway alternative may be prudent and warranted in the high-risk patient if the clinical situation is appropriate.
14. The airway team should have ready access to the equipment recommendations put forth by the ASA Guidelines.

References

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