Exchanging an endotracheal tube (ETT) in the high-risk patient is challenging and may lead to life- threatening complications. Adjunct laryngoscopy allows a pre-exchange examination to assess the airway anatomy and may assist with both airway visualization and clearing the pathway for ETT exchange.1 Limited visualization because of the indwelling ETT, secretions, edema, cervical spine appliances, orogastric feeding tubes, and restricted positioning capabilities may restrict the usefulness of laryngoscopy, especially conventional direct laryngoscopy (DL).2
Video laryngoscopy (VL) technology offers improved visualization and intubation success in many difficult airway situations.2–6 The overall success of airway assessment in the high-risk difficult airway patient and the safety of ETT exchange may benefit by incorporating VL technology.2,7–9 One analysis found that in patients who had “no view” by conventional laryngoscopy (DL) during pre-exchange airway assessment, 94% were afforded a full or near-full glottic view with subsequent use of VL technology. Furthermore, improved visualization during the airway exchange catheter (AEC)-assisted ETT exchange resulted in a first-pass success rate of 96% and VL served as its own rescue device when accidental removal of the AEC occurred during the exchange.2 The primary hypothesis tested whether VL + AEC-assisted ETT exchange is more efficient (fewer attempts) and decreases risk (fewer complications) when compared with a group of historical controls who underwent DL + AEC-assisted ETT exchange. A secondary hypothesis tested was whether VL-assisted pre-exchange airway assessment will offer improved periglottic visualization in patients with a “poor view” on DL-based airway assessment.
An ongoing intensive care unit (ICU)-based ETT exchange database (2001–2014) was reviewed. Beginning with the availability of VL in late 2006, a nonrandomized study comparing VL + AEC-assisted ETT exchange with DL + AEC-assisted ETT exchange (historical control group) underwent IRB approval (2007) with a waiver of consent for the procedure during a 90-month period (2006–2014). Exchange procedures took place in 1 of the 5 ICU locations or the postanesthesia care unit in a tertiary care, 800-bed, level I trauma center and were reviewed retrospectively. Elective operating room ETT exchanges were excluded.
In preparation for the exchange procedure, a review of the medical record, discussion with the ICU staff, and physical assessment of both the patient and their airway were undertaken. A board-certified anesthesiologist from the Department of Anesthesiology alone (32%) or with anesthesia resident assistance (68%) performed all ETT exchanges. All patients were administered 100% oxygen and positioned, if applicable, to optimize airway management, for example, ramping. Pre-existing ICU IV sedatives and analgesics were continued or supplemented as needed. Neuromuscular-blocking drugs were administered for the ETT exchange in 65% of patients at the discretion of the airway team.
The historical control group patients each underwent a DL-based pre-exchange airway assessment followed by a DL + AEC-assisted ETT exchange. The laryngoscopy grading system was based on the modified Cormack-Lehane system of the unintubated glottic view (Table 1). All study patients first underwent a screening DL (MacIntosh size 3 or 4) to assess the ability to view the periglottic anatomy. A poor view (grade III, IV) prompted a VL-based airway assessment, and the VL view was graded (Table 1). A VL + AEC-assisted ETT exchange was then performed using either the GlideScope-GVL (reusable blade, 2006–2009) or the GlideScope Cobalt (disposable blade, 2009–2014) (Verathon Medical, Bothell, WA). The McGrath Video Laryngoscope (Aircraft Medical, Edinburgh, Scotland) was incorporated as a rescue if mouth opening was limited.10
Details of the ETT exchange procedure were collected from the preprinted airway management procedure form that is completed by the airway team for the medical record. A duplicate copy is used for billing and departmental quality assurance. Patient age and gender, height and weight, reason for the exchange and the number of attempts made, complications, and rescue device intervention were recorded. Significant patient injury and complications were detailed by discussion with the airway and ICU teams and review of the medical record. Information was transferred to the ongoing Quality Assurance ETT exchange computer database. The data collection was analyzed to isolate those patients with a poor view on pre-exchange (DL) laryngoscopy and who subsequently underwent a DL + AEC-assisted ETT exchange. These cases served as the historical control group (n = 337). Double-lumen tube (DLT) exchange, inability to place the AEC for the exchange, positional exchanges of the ETT (e.g., nasal-to-oral), an inability to place the VL device into the patient’s oral cavity, and when a clinical decision was made not to proceed with the exchange procedure (after the pre-exchange assessment) were exclusions from analysis for both the historical and the study groups. After acquisition of VL technology and primarily based on improved airway visualization, encouraging results were noted during preliminary deployment for ETT exchange, thus prompting interest in this research analysis. Endpoints included success rate, complication rate, number of attempts, and number of rescue interventions.
The current analyses are based on a sample of 328 patients (VL + AEC) with comparisons being made with a historical cohort of 337 patients (DL + AEC). All relevant entries in the STROBE checklist have been addressed in the manuscript. The Student t test was used to evaluate group differences in quantitative variables, and the contingency χ2 test was used for categorical variables. The exact McNemar test for paired proportions was used to compare the best DL and VL views. The success rate based on the number of attempts (first, second, third+) is presented with the 95% confidence limits for the binomial proportion. Relative risk calculations represent the risk of various complications between groups (DL versus VL). The asymptotic confidence limits were estimated using the PROC FREQ procedure in SAS with the BINOMIAL or RELRISK options specified, as appropriate. All analyses were performed using SAS version 9.2 (SAS Institute, Inc., Cary, NC). A value of P <0.05 was considered statistically significant.
Five hundred seventy-five patients were evaluated for VL-AEC exchange. Those with adequate DL glottic view (grades I/II, n = 91) on their pre-exchange airway evaluation were excluded from VL assessment leaving 484 cases with a poor view (grades III + IV). To assure uniformity of the ETT exchange case mix, after exclusions of selected cases, 328 cases were appropriate for analysis (Table 2). Demographic and difficult airway risk factors were similar between the historical control and the study groups (Table 3). Exchanges were performed primarily for (1) ETT compromise (cuff leak, kinking, luminal narrowing, pilot balloon dysfunction); and (2) changing the ETT size or type, for example, upsizing for bronchoscopy, pulmonary toilet, or difficult weaning (Table 3).
Despite optimal positioning, suctioning, and pharmacological preparation of the patient, the vast majority (83.7%) of the DL-screened patients had, at best, a grade III or, at worst, grade IV view on laryngoscopy, thus demonstrating the relative suboptimal performance of DL in this high-risk population (Table 4). The plethora of risk factors increasing airway difficulty such as obesity, cervical spine immobilization, trauma service patients, and aggressive fluid resuscitation leading to head/neck edema afflicted many patients, thus limiting “line of sight” of DL (Table 3). VL technology offered a markedly improved degree of glottic visualization (Table 4). A full or near-full view (grade I, II) was achieved in 288 of the 328 (87.8%) cases.
Nineteen patients were excluded from analysis because of an inability to place both the DL and the VL devices (trismus, halo-vest, mandibular wiring, or other anatomical constraints; Table 2). Successful DL blade insertion was possible in 5 of the 19 patients, but no view was obtained. The McGrath VL was used successfully in 9 patients who had failed GlideScope placement. The McGrath VL’s disarticulating blade handle assembly afforded blade placement followed by handle reattachment and offered grade I/II views in 8 cases and grade III in another.10 Fourteen cases were disqualified from the AEC exchange group (Table 2) comparison based on inaction by the airway team. Severe periglottic swelling (n = 10) or no view (n = 4) on VL assessment prompted aborting the ETT exchange entirely.
ETT Exchange Procedure
The first-pass success rate for ETT exchange was markedly different between the 2 study groups (67.7% DL versus 91.5% VL, P = 0.0001; Table 5). The improved glottic visualization increased the first-pass success rate of reintubation and decreased the incidence of complications (Table 5). Quality control comparison of the study group with the historical control revealed no trends over time within groups (Figs. 1 and 2). The DL group had several significant, occasionally life-threatening complications that far outpaced the VL group (Table 6). It appears that the restricted glottic visualization offered by DL may have contributed to an increase in the incidence of hypoxemia, esophageal intubation, bradycardia, cardiac arrest, and the need to use rescue alternatives. The incidence of mild and severe hypoxemia was at least 1.5-fold and 4.2-fold higher, respectively, in the DL + AEC group. Likewise, improved airway visualization likely influenced the marked reduction in ETT misplacement into the esophagus because of AEC coiling (folding over of the thin-walled AEC because of excessive force applied by the operator onto the advancing ETT), the AEC exiting the trachea, or poor visualization.
Difficult reintubation lead to multiple intubation attempts, resulting in hypoxia-driven bradycardia in 5 of the 6 DL-AEC cardiac arrest cases (in 1 case ventricular tachycardia occurred secondary to a tension pneumothorax [PTX] related to high-pressure “jet” oxygen delivery). Thickened mucous, blood, or secretions led to acute ETT luminal obstruction and hindered ventilation and oxygenation just before or immediately after the ETT exchange, leading to an additional 5 cardiac arrests (DL 3, VL 2). Furthermore, 1 case of “near-arrest” (severe desaturation, bradycardia, tension PTX) was related to high-pressure jet oxygen delivery via the AEC during DL-AEC exchange that required needle decompression and closed thoracostomy. The use of other accessory methods to resecure the airway (VL 1, laryngeal mask airway 4, bougie 2, cricothyrotomy 1, or bronchoscopy 10) was heavily weighted toward the DL + AEC group (Table 6). ETT exchanges managed by VL had a very low incidence of using additional airway equipment because VL served as its own rescue device barring 2 laryngeal mask airway rescues (Table 6). Thirty-five cases excluded from data analysis for the inability to pass the AEC were managed by VL-assisted exchange (34 of 35 successful on first attempt).
PTX after exchange occurred in 7 in 665 cases and was identified by postintubation radiograph (4 cases, asymptomatic; 1 case, desaturation with ↑inspiratory pressures) or by hemodynamic/oxygenation deterioration (2 tension PTX). The incidence of PTX was higher in complicated exchanges: 2+ attempts (6 of 7 PTX), >10 L IV fluid resuscitation within 48 hours (5 of 7 PTX), positive end-expiratory pressure 8+ (6 of 7 PTX), trauma service (5 of 7 PTX), and attempted high-pressure jet oxygen delivery via the AEC contributed to 2 PTX (1 tension). Three of the 7 PTX were pre-existing (small yet visible on computed tomography scan or chest radiograph) and asymptomatic. Of note, only 2 of the 7 PTX cases (0.3%) could be plausibly explained by AEC “trauma” as a contributing or causative factor.
ETT exchange in the critically ill ICU patient with a difficult airway is challenging and presents formidable risks. In such patients, pre-exchange airway assessment is an opportunity to garner valuable clinical information to assist with exchange strategy or alternatively allow corrective maneuvers for a “cuff leak” emanating from an unrecognized herniated ETT cuff/tip (partial/complete extubation). Laryngoscopy, a valuable adjunct to the AEC, facilitates ETT advancement by opening a pathway to the trachea. DL offers suboptimal and unreliable visual assessment of the difficult airway. In contrast, VL offers a marked improvement in viewing capabilities during the pre-exchange airway assessment. When compared with a historical sampling of ICU patients with difficult airways who underwent ETT exchange using a DL-AEC approach, the combination of VL-AEC markedly improved the first-pass success rate while reducing the incidence of airway and hemodynamic alterations and the need for rescue interventions. In our study, VL also frequently served as its own rescue device when management difficulties arose.
Current literature regarding ETT exchange is relatively sparse, despite the profound patient safety implications2,7–9,11 Airway management schema support the idea of maintaining continuous access to the airway for ETT exchange.11–14 Although AEC-guided exchange is a simple concept, it poses potentially great danger even if used cautiously by experienced personnel.11,13–21 McLean et al.11 recently reported that AEC-assisted ETT exchange (operating room) failed in 13.8% of cases overall, and this rate was further exaggerated for DLT exchange. Unfortunately, the exchange method was not described although the literature suggests VL may be advantageous in DLT cases.11,22–24
The overall success of VL and its ease or difficulty may be directly impacted by one’s ability to visualize the airway. Adequate periglottic visualization has expanded the airway team’s knowledge and appreciation of previously less well-recognized factors that may hinder ETT advancement: a narrow glottic opening, periglottic swelling or injury, bevel impingement on airway tissues, accidental AEC dislodgement, or AEC bowing/coiling may singly or in combination thwart tracheal reintubation efforts. Each may herald airway injury, delay oxygenation, interrupt ventilation, and contribute to airway and hemodynamic complications.2,11
The historical group of DL + AEC cases was selected specifically for their poor view that was assessed on pre-exchange laryngoscopy and reflects that patient safety issues are more likely when visualization is suboptimal. Poor glottic visualization during ETT exchange begets multiple attempts, which escalate airway and hemodynamic complications and reliance on backup rescue devices, as is the case for emergency tracheal intubation.25 Using VL technology appears to reduce adverse events by affording more timely and efficient ETT exchange. This approach is consistent with the recommendation of the American Society of Anesthesiologists Task Force to limit laryngoscopic attempts.12,25
In instances when the ETT advancement is difficult, periglottic visualization is even more beneficial. The operator may determine whether the ETT tip is obstructed by airway tissues, glottic narrowing, airway trauma or swelling, or AEC coiling/bowing. The ability to continuously observe the presence of AEC within the airway as well as its depth imparts additional safety implications. Because of the curve of the AEC around the oral-to-pharyngeal axis, the AEC typically runs along the posterior pharyngeal wall mucosa, then angles anteriorly to traverse the posterior glottic opening (Fig. 3) and stretches the glottis posteriorly, causing a concomitant deformation of the arytenoids from a round configuration to ellipsoidal (“racetrack or paper clip shape”; Fig. 4, A and B). Medial repositioning of the arytenoids may contribute to bevel impingement. This glottic reshaping may be further amplified by the downward force applied to the AEC when the ETT is being advanced toward the vocal cords. Bevel impingement has been noted during bronchoscopic intubation (arytenoid and vocal cords) but may afflict any “Seldinger” technique that delivers an ETT transglottically.26–29 Familiarization with caveats for reducing ETT tip impingement may enhance timely advancement (Table 7). Smaller diameter AEC models, for example, 11 F and 14 F, paired with a relatively large-diameter ETT, for example, 8.0, led to a sizable AEC-ETT gap and increased the likelihood of impingement and ETT tip wobble.27 Careful consideration should be given to pairing the ETT and airway conduit to minimize the gap.27Table 8 outlines the cross-sectional area of various conduits commonly paired with an ETT, for example, 7.0 ETT = 38.5 mm2, 8.0 ETT = 50.2 mm2 (Figs. 5 and 6).
AEC coiling, although unusual and typically restricted to the smaller caliber 11 F AEC, may lead to misplacement into the esophageal intubation, intubation delay, and loss of the airway. The bowing tendency of an AEC, likely a precursor of coiling from a reduced vector of force, appears inversely related to its diameter but will be directly related to the degree and vector of force applied during ETT advancement (Fig. 7). Although AEC coiling may completely interrupt ETT advancement, bowing exaggerates the angle of entry the ETT follows as it enters the larynx and contributes to entrapment of the ETT tip on the periglottic tissues. VL visualization has enlightened the airway team to these morbidity forerunners. Use of the smaller caliber AEC may be unavoidable because of a pre-existing small-caliber ETT, luminal kinking or narrowing, or a DLT exchange. To bolster the AEC and increase its “firmness” while reducing the “gap,” a second AEC (Aintree, Cook Medical, Inc.) may be placed over the 11 F and 14 F models (Aintree bronchoscope duet for laryngeal mask airway intubation)26 (Fig. 8). Conversely, a designated “DLT” AEC (increased length, softened tip, increased rigidity, AEC-EF, Cook Medical, Inc.) may reduce bowing, deter coiling, and ease ETT advancement.
A pre-exchange airway assessment may garner useful information for augmenting the execution of the exchange procedure as well as strengthen diagnostic prowess when, for example, asked to exchange the ETT for a cuff leak. This data review suggests the pre-exchange airway assessment was responsible for identifying a substantial number of patients (n = 171) with ETT cuff/tip herniation at or above the glottis as the etiology of the cuff leak. The patient safety implications of detecting the unrecognized, proximally displaced, herniated ETT are poignant factors lending support to performing such an assessment. “Blind” advancement of an AEC into a displaced ETT (unrecognized completely extubation) and the administration of a neuromuscular-blocking drug could lead to catastrophic patient injury.
ETT exchange is a risky procedure, and the fundamentals of airway management must be practiced. Advanced planning, proper positioning, patient preparation coupled with a strategy for both the procedure, and its rescue are requisite. Patient safety will be complimented by incorporating advanced laryngoscopic devices when combined with advanced operator skill, judgment, and patient selection.
The limitations of this study include several potential biases: the retrospective nature of the analysis, the comparison with a historical cohort selected specifically to represent a “difficult airway patient,” and the concern of any single-center data analysis. Moreover, data collected from procedure notes may be plagued by confounding variables such as the underreporting of complications, the quality of the laryngoscopic view obtained, and the actual number of laryngoscopic attempts performed. Additional studies are encouraged to confirm or refute our findings.
In conclusion, ETT exchange in the critically ill ICU patient is risk-laden and poses life-threatening consequences. The findings of this review support using VL-assisted AEC-based ETT exchange in the known or suspected difficult airway patient. Marked improvement in periglottic visualization led to a higher first-pass success rate and a reduction in airway and hemodynamic critical events when compared with DL-AEC exchange. VL serves admirably as a rescue device when the use of the AEC is limited or the exchange procedure goes awry. Continuous observation of the airway and the AEC position and depth are key elements for improving patient safety. A pre-exchange airway assessment appears to be a valuable procedure for both planning the exchange and uncovering other unrecognized airway maladies, for example, unrecognized partial or complete self-extubation. Although the AEC is not without its detractors nor is it risk-free,11,13,14,16,18,20,21,30–33 it serves as an integral role in maintaining continuous airway access in the high-risk patient.12 The potential advantages of continuous glottic visualization during high-risk ETT exchange are outlined in Table 9.2
Name: Thomas C. Mort, MD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: Thomas C. Mort has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.
Name: Barbara H. Braffett, PhD.
Contribution: This author researched the data, performed analysis, and contributed to writing the manuscript.
Attestation: Barbara H. Braffett approved the final manuscript, which represents original work.
This manuscript was handled by: Avery Tung, MD.
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