Video-Assisted Laryngoscopy

Undifferentiated Airway

It is unclear whether the use of VAL improves intubation success in routine (not difficult) airway management in the hands of experienced airway practitioners. Compared with DL, the laryngeal view is improved when using VAL. The improved view may be attributed to a magnified video view, the anterior curvature of the laryngoscope blade, visual axis extension, or a reduced need to align a direct visual axis. Although DL is associated with failure when a laryngeal view cannot be achieved, VAL frequently overcomes the obstacle of an inadequate laryngeal view. However, the improved laryngeal view does not necessarily translate to increased intubation success. As the success rate for DL in normal airways is very high, it remains to be determined whether or not the use of VAL would further improve intubation success compared with DL in routine airway management.

When managing normal airways, VAL tends to be a slower intubation technique. There may be several reasons why practitioners require more time until successful intubation when using a VAL, including visual attention in two different places, difficult ETT passage, or lack of experience with a newer technique. However, whether longer intubation times associated with VAL cause an increased incidence of oxygen desaturation or intubation failure has never been confirmed.

The management of the routine airway by anesthesiologists has raised interesting questions, and many argue that VAL may not be helpful for the routine airway based on the evidence reviewed above. However, most of these studies investigated the role of acute-angle VLs for routine airway management. In contrast, VAL with standard laryngoscope blade designs offers the benefits of two worlds: the familiarity of the use and simplicity of ETT passage combined with the availability of a video image if needed in an unanticipated DA. Interestingly, a recent systematic review highlights that VAL reduces intubation failure across study cohorts.

In summary, VAL improves the laryngeal view for routine airway management and likely reduces intubation failure, but large studies confirming improved success rates for routine airway management in experienced practitioners’ hands are lacking.

Novice Practitioner

VAL offers benefits for practitioners who have less experience with airway management. Compared with DL, intubation success rates are higher with VAL in novice practitioners’ hands. ^, This benefit is achieved with both video-assisted standard and nonstandard laryngoscope blades. Additionally, instructor-guided laryngoscopy using a video device also appears to accelerate DL skills.

A long-standing concern regarding VAL is that its routine use for any potentially DA scenario might impair DL skills. Indeed, using VAL as the first choice for airway rescue as well as for patients with predicted difficult intubation will lessen the exposure to difficult DL over time. Nevertheless, the use of VAL can also be part of the solution: regular training using video-assisted devices that feature standard blades allows a trainee laryngoscopist to perform the laryngoscopy under direct vision while an instructor looking at the screen can use that information to teach DL skills. As such, it has become common practice for many instructors to use standard blade VAL when working with novice laryngoscopists.

A number of experts believe that VAL is easier to learn than other intubation techniques. To date, however, competence with various techniques has not been studied rigorously. Many trials with VAL are difficult to interpret because it is unclear if practitioners in the studies had adequate competence with each particular device. On the other hand, it is useful to understand if the early adoption of a technique can maintain or improve existing success rates with conventional DL. In a longitudinal observational trial Cortellazzi and colleagues determined the number of intubation attempts required to achieve more than 90% reliability of first-attempt intubation success with a CL grade 1 view with the GlideScope. They observed that 76 intubations were necessary for this level of proficiency. These findings are novel because they suggest that competency with VAL may require as much training as needed to become proficient with DL; others found that 57 DL attempts are necessary to achieve intubation success rates greater than 90%.

In summary, novices have higher intubation success with VAL compared with DL, but the learning curve for either technique appears not to be different as both techniques require about the same number of procedures before proficiency is achieved. Furthermore, experience with one VAL technique may not translate to similar performance with another VAL technique.

Predicted Difficult Intubation

Patients with predictors of difficult laryngoscopy likely realize more benefit when VAL is utilized. Although the majority of related trials were not powered to effectively compare success rates, a few demonstrated a reduction in intubation difficulty scale (IDS) scores with better views when VAL was used. ^, Only a handful of clinical studies so far have defined “intubation success” as the primary end point in comparing VAL with DL; in a randomized crossover study intubation success rates were higher with the Pentax-AWS than with DL in patients under simulated difficult intubation conditions created by manual in-line stabilization. Others observed an increased success rate of tracheal intubation in patients with higher Mallampati scores when VAL was studied in a large randomized controlled trial. Another randomized controlled trial explored VAL success in a large group of practitioners while applying broader inclusion criteria for DA. These authors demonstrated higher intubation success on the first attempt with a video-assisted direct laryngoscope compared with DL. Together, the available data suggest that VAL indeed improves intubation success in patients with predicted DA, and the most recent American Society of Anesthesiologists (ASA) Guidelines for Management of the Difficult Airway reflect this evidence. Nevertheless, additional well-designed trials are needed to understand whether the same is true for different intubation environments and other VAL devices.

Unanticipated Difficult Intubation

Case reports have confirmed that VAL can be used to rescue an intubation that has failed with DL. In a large, two-center database evaluation of 71,570 perioperative intubations VAL rescued failed DL in 94% (224/239) of cases. In a study of another VAL technique 99% (268/270) of intubations were successfully rescued after practitioners failed to achieve an adequate laryngeal view with DL. These studies provide strong evidence because these rescue successes reflect the use of different VLs by a large number of practitioners in diverse patient populations. Compared to other techniques used to rescue failed DL, VAL is associated with a higher rescue success rate than other commonly employed techniques. It underscores the particular benefit of having VAL available for the unanticipated DA at every site that may encounter such patients. Furthermore, as repeated DL attempts are associated with morbidity and mortality, ^, the use of VAL as the next step after failed DL may help to further improve intubation safety for affected patients, as reflected in the most recent guidelines. Nevertheless, other airway management techniques (e.g., flexible scope intubation [FSI]) retain an important role for airway rescue when primary techniques have failed. Therefore experts agree that practitioners always should use the airway devices with which they feel most comfortable and have the highest proficiency.

Video-Assisted Laryngoscopy for Awake Airway Management

Awake VAL has been evaluated in direct comparison to awake FSI in the scenario of potential DA. Findings demonstrated similar performance with both techniques; however, the validity of the findings is somewhat limited because patients were sedated rather than “awake,” patients were excluded when presenting with neck pathologies, and the study design allowed post-randomization exclusion. In another study of awake nasal intubation with flexible bronchoscopy versus VAL both techniques also performed similarly. In this study patients in both interventional groups were sedated with the goal of avoiding recall of the procedure. As such, findings from both studies may not apply to the true “awake” intubation. Nevertheless, one study demonstrated lower sedation requirements for awake VAL than FSI. Despite these limitations, awake VAL may be a technique that can be acquired and maintained more easily than flexible bronchoscopy and may change the practice of awake intubation in the future. Accordingly, the Difficult Airway Society’s recent guidelines on awake tracheal intubation include VAL as an acceptable approach.

This technique, however, likely requires some careful practice and prior experience with VAL. Because the vallecula may be quite sensitive, adequate topicalization and/or patient sedation may be necessary before inserting a laryngoscope in this location. Furthermore, the practitioner should be careful not to apply too much suspension pressure on this location because it is poorly tolerated. Lastly, ETT passage may require careful attention. A rigid stylet may be used within the ETT for unchanneled devices, while channeled devices should be carefully manipulated such that the ETT passes gently into the trachea without traumatizing laryngeal or tracheal structures.

Video-Assisted Laryngoscopy Outside of the Operating Room

Early investigations in various clinical environments outside of the operating room (OR) suggest a potential benefit when VAL is used. These environments are challenged with both DA scenarios and practitioners who perform tracheal intubation less frequently than their colleagues in the ORs. In critical care and emergency medicine environments VAL is associated with a higher intubation success rate in patients with a broad selection of indicators. Confirming these observations, one randomized controlled trial recently found higher intubation success with VAL compared with DL in critically ill patients. In contrast, in the emergency medicine environment one randomized trial found no difference between VAL and DL. In fact, intubation time was longer and survival worse in a subgroup of head-injured patients when VAL was applied; however, only limited conclusions can be drawn from the above studies because they involved select patient populations and a small number of practitioners. Two large randomized trials also failed to confirm the benefit of VAL over DL in the ICU. ^, In the larger study patients in the VAL arm suffered more hypoxemia and more frequent severe life-threatening complications. These comparative trials all have study limitations as patient inclusion, practitioner experience, and intubation technique are difficult to optimize in these study settings. Nonetheless, the assimilation of current data continues to suggest that VAL does not yet demonstrate improved patient outcomes outside of the OR.

In obstetric patients VAL has been used for emergency airway management, potential difficult intubations, and rescuing failure of DL. This distinctive airway management setting is typically challenged by its remote location from other ORs, a patient population prone to having a DA, and, often, a need for tracheal intubation under the most pressing circumstances (i.e., for emergent crash cesarean section). Therefore it has been recommended that VAL be available for all obstetric general anesthetics. This unique environment is discussed in further detail in Chapter 37 .

Finally, in prehospital emergency medicine VAL is associated with a reduction in the number of intubation attempts and a shorter laryngoscopy time than DL. ^, However, most studies so far have had a retrospective design; therefore the interpretation of the results requires some caution. Likewise, four prospective randomized trials have failed to demonstrate any benefit of VAL compared with DL, and intubation success was worse. Nevertheless, as above, the interpretation of these results is limited: in one of the studies practitioners received little training in the instrument studied, the Airtraq, which so far is not well established in this practice environment. The failure of the GlideScope and AWS to perform well in this environment, however, was surprising and was attributed to difficulties with ETT passage despite an adequate laryngeal view or contamination of the lens from oral substances. Nevertheless, prospective randomized studies are difficult to perform in this clinical environment. Finally, the practice environments of these trials (Europe and Asia) may not reflect clinical practice in other regions of the world with vastly different emergency medical systems.

In summary, VAL is becoming more accepted in clinical practice environments outside of the OR, but studies have not yet ubiquitously confirmed the benefits of this technique. Observational data suggest benefits when using VAL, but so far, the results of prospective randomized trials have been mixed. More prospective randomized controlled trials are needed to determine the potential superiority of VAL over DL in any of these practice environments.