Our study reveals important new information about the effectiveness of combined techniques (VL + FOB and VL + TCI™) compared to other advanced intubation techniques (awake FOB, and asleep FOB) when managing difficult intubations in a real-world setting.
We found significant differences in first pass success, failure of primary technique, speed, ease of use, and patient injury between the advanced airway techniques studied.
First attempt intubation success
Combined techniques (VL + FOB and VL + TCI™) achieved the highest first intubation success rate of (88.7%) This was significantly higher than FOB awake (74.2%, P < 0.001). and higher than FOB asleep (80.7%, P = 0.06) In subgroup analysis of combined techniques, VL + TCI™ had the highest rate of first attempt intubation success of all techniques studied (90.2%). This was significantly higher than FOB awake (74.2%, P = 0.002) and higher than both VL + FOB (86.4%, P = 0.63) and FOB asleep (80.7%, P = 0.06).
The rate of first attempt intubation success rate found for VL + FOB in this study is consistent with those found by Mazzinarri et. al. 10 and Lenhardt et.al. 13 This first attempt intubation success rate found for VL + TCI™ is consistent with that found by Shah et.al 11 in their case series of rescue intubations.
First attempt intubation success is important as multiple attempts are known to increase both major complications and mortality. A recent large muti-centered study demonstrated a significant increase in ICU mortality after just one attempt failure in the critically ill.20
In subgroup analysis of combined techniques, use of a TCI™ as a dynamic stylet had a higher rate of first pass success than when a FOB was used as a dynamic stylet. This is interesting as both TCI™ and FOB possess flexible shafts and articulating tips which are important for dynamic tracheal access. 10 One important difference is that a FOB requires both the right and left hand for operation, while the TCI™ requires only the right hand. Use of a FOB as a dynamic stylet necessitates a second operator handles the VL during the procedure. The TCI™ can be operated entirely with the right hand allowing a single operator to manage the intubation with VL with the left hand and TCI™ in the right. This enables a single operator to manage the entire intubation by themself. The need to coordinate two operators for VL + FOB adds complexity and may reduce performance and effectiveness of VL + FOB in comparison to VL + TCI™. Further studies are needed to understand the role single vs double operator execution plays in first attempt success.
Failure to intubate with the primary technique
Combined techniques as a group had the lowest rate of “failure to intubate with the primary technique” at (1.8%) followed by FOB asleep (4.6% P = 0.11) and FOB awake (9.2% P = 0.002). In subgroup analysis, the failure rate for VL + TCI™ was the lowest (1%) of all techniques studied. The failure rate for VL + FOB was 3%. These failure rates are consistent with those found by Mazzinari et. al. 10 for VL + FOB and Shah et. al. 11 for VL + TCI™.
The failure rates of FOB asleep and FOB awake are notably higher than those found in the literature. This study was performed at a teaching institution which may account for a higher rate of failure despite removing advanced intubations performed for educational purposes. Our criteria for failure was: “three or more attempts using the same device” as this is a known point of risk inflection. It may be more stringent than other studies 1 It is important to note that most studies of FOB do not define failure by number of attempts but simply by abandonment of the procedure. El-Boghdadly et. al. did report that 4.2% of patients required greater than 1 attempt. The duration of a single attempt is not reported.21 As FOB awake does not require the interruption of breathing, an single attempt may not be limited by desaturation but only by the ability of the operator and/or the patient to tolerate the attempt.
The overall performance and ‘in room to intubated time’ of combined techniques compared to awake FOB or asleep FOB is of particular interest as FOB has long been considered the “gold standard” for managing difficult intubations with reported success rates of up to 99%. 17 22 While risk with multiple attempts is well established, risk related to aggregate time attempting to intubate with FOB awake has not been studied. One can only wonder if the 99% success rate of FOB reported in the literature comes at the cost of multiple and/or lengthy attempts. Persistence with a single technique is a known risk factor for airway disasters. 16
“In room to intubated” time: Combined technique as a group (either VL + TCI™ or VL + FOB) was found to have a significantly shorter “in room to intubated” time (13.0 min) than either awake FOB or FOB asleep (15.1 mins and 21.2 min, P = 0.002.) In subgroup analysis VL + TCI™ was found to have a significantly shorter in room to intubated time” (12.1 min) than FOB asleep (15.1 min, P < 0.001) and FOB awake (21.2 min, P < 0.001). VL + TCI™ was found to have a shorter “in room to intubated” time (12.1 mins) than VL + FOB (14.3 mins, P = 0.12) This is important as operating room time is an expensive and limited resource. Joseph et.al. studied ‘in room to intubated’ time differences in different awake and asleep intubation techniques and found significant increases in time associated with awake vs asleep: FOB 22 To the best of our knowledge, ‘in room to intubated times’ for VL + FOB, and VL + TCI™ have not been studied. The causes of these increased times cannot be determined by our study. Possibilities include: (1) increased time due to intrinsic complexity of equipment needed to set up and execute each technique, (2) management and coordination of extra personnel in room for those techniques requiring 2 sets of educated hands, (3) aggregate time spent in active intubation attempts.
Further study of what factors account for the increased ‘in room to intubated’ time is important. Minutes spent setting up equipment or preparing the patient is expensive in terms of OR time but should not increase risk to the patient. Minutes spent in prolonged single attempts or multiple intubation attempts may cause harm. Complex and cumbersome intubation equipment increases the mental task load of providers as is evidenced by the increase in training numbers and continued practice to maintain complex FOB intubation skills. Increased mental task load is known to decrease performance and increase time need to complete a task, and may result in an increased risk of harm in the context of intubation. 18 23 FOBs are complex and known to require specialized training and skills to set up and operate.24 22 This complexity may require a second set of educated hands in order to set up and execute the procedure. The aggregate time spent in intubation attempts is unknown for any of the techniques studied however the ‘in room to intubation time’ was found to be significantly correlated to the number of intubation attempts made with the primary technique. (See table 3.)
Variable
|
1: N = 749
|
2: N = 132
|
≥ 3: N = 51
|
P-value
|
Minutes from in room to intubated - Mean (SD)
|
15 (11)
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21 (12)
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30 (16)
|
< 0.001*j
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Median (IQR)
|
14 (10, 18)
|
19 (13, 24)
|
27 (20, 39)
|
-
|
Range
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(1, 211)
|
(0, 84)
|
(8, 96)
|
-
|
j Jonckheere-Terpstra test.
*indicates statistical significance.
Table 3. Minutes from in room to intubated by number of attempts.
Multiple attempts take time, it seems reasonable to assume that this accounts for a portion of the ‘in room to intubated’ time differences observed in our study.
Operator reported ease of intubation. Combined techniques were rated as ‘easy’ significantly more often (72%) than FOB awake (38.2%, P < 0.001) and more often than FOB asleep (62.9%, P = 0.12). In subgroup analysis, VL + TCI™ was rated as ‘easy’ significantly more often (83.3%, P < 0.001) than all other techniques studied. This is important as “difficult” implies an increased mental task load during the procedure which can lead to decreased operator performance and may lead to an increased risk of harm.
Operator reported trauma. Combined techniques as a group were reported as “atraumatic” more often (91.1%) than either FOB asleep (89.4%, P = 0.91) or FOB awake (75.8%, P < 0.001). VL + TCI™ was rated as “atraumatic “at a higher rate (96.1%,) than any other technique studied; VL + FOB (83.3%, P < 0.009), FOB asleep (89.4%, P = 0.10), and FOB awake (75.8%, P < 0.001). These differences are interesting in that all techniques essentially use a dynamically controllable stylet for tracheal access. Multiple intubation attempts are known to increase the risk of patient harm.
We speculate that the higher first pass rates and lower failure rates found within the two combined techniques may be the result of effectively separating the role of visualization and the role of tracheal access into two separate devices: VL for visualization and a dynamic stylet for precision tracheal access. If we focus of the descriptions of the role of FOB in combined technique in the literature, over time one can see less interest in the FOB’s visualization capabilities and more interest in its’ navigational capabilities. The first reported combined technique series published by Sgalambro et.al. 3 described using DL in combination with a FOB. The role of DL was simply as a blade to clear the airway for the passage of a FOB which provided both visualization and precision tracheal access combined in one device. The DL had little or no role in visualization. Lenhardt et.al.’s 13 study combined VL and FOB using VL for visualization and FOB for both navigation and visualization. In Mazzinari et.al. 10 study, the role of the FOB had atrophied to simply to that of a dynamic stylet without the use of its optical capability. Shah et.al. 11 published a series in which VL was combined with the TCI™, a purpose-built articulating introducer with no intrinsic visual capabilities. With the introduction of the VL for visualization and diminishing importance of a dynamic stylet's optical capabilities, reported first-pass success in anticipated difficult intubations has trended upward. Lenhardt et.al. 13 reported an 87% first attempt success rate (VL and FOB visualization), Mazzinari et.al. 10 91% (VL only visualization, FOB simply a dynamic stylet), and Shah et.al. 10 94% (VL only visualization, TCI™ purpose built dynamic stylet). This is an observation only. These studies were not designed for comparability. Studies designed to test this hypostasis properly would be of interest.
In our study, combined techniques as a group outperformed both FOB awake and FOB asleep in all endpoints measured. In subgroup analysis VL + TCI™ outperformed all other techniques studied. The main limitations to widespread dissemination of combined technique are; cost, immediate availability and the need for two operators for execution.24 10 All of these drawbacks are associated with the FOB which is being cross-purposed as a dynamic stylet. In many cases, the FOB optical capabilities are not utilized, and that very feature may negatively affect the effectiveness of the combined technique in terms of ease of use, and cost. Further study is needed to understand this point
The TCITMis a novel and innovative articulating introducer without intrinsic optical capabilities. The capability and effectiveness of the TCI™ in combination with VL found in this study supports the need for further investigation to gain a greater understanding of the capabilities and effectiveness of different combined techniques, such as VL + FOB and VL + TCI™, in a wider variety of settings.
Limitations
This study has several important limitations mainly related to the single-center, retrospective design. First, this study is not controlled for technique selection bias, provider experience with a technique, availability of equipment, patient specific physiology, or patient anatomical features that might influence technique choice and outcomes. Second, this is a single-center study and caution must be exercised in generalizing these results widely. Third, Table 1 demonstrates significant differences in difficult intubation risk factors between groups. These differences might influence the performance or different techniques in our study. Fourth, this study includes only operating room intubations performed by anesthesia providers. Performance in other environments may vary.
Despite these limitations we believe this data provides important new insights into the performance of different advanced intubation techniques in the natural workflow of a large teaching hospital’s surgical system.
Further studies, in diverse settings are needed to understand if the superior performance of combined techniques found in this study are generalizable to other systems and settings.