Abstract
Innovations and challenges for lung separation or isolation have evolved during the last few years. In this chapter, we present the up-to-date, robust evidence available during the previous five years supporting the positions of the different devices, techniques, and tricks for their use in adult and pediatric patients undergoing various thoracic surgical interventions. Additionally, we presented an update on lung isolation in patients with airway difficulty and the suggested training level to master these techniques.
Abbreviations
BB
Bronchial Blocker
CT
Computerized Tomography
DLT
Double-Lumen endobronchial Tube
ETT
Endotracheal Tube
FOB
Fiber Optic Bronchoscope
MPR
Multi-Planar Reconstruction
RCT
Randomized Controlled Trial
TD-C
Transverse “outer” Diameter of the Cricoid cartilage
VL
Video Laryngoscope
1
Introduction
Thoracic anesthesia has evolved during the last few years because of innovations and challenges in modern thoracic and pulmonology procedures. This chapter presents current novel lung isolation options, clinical tricks, and training required to manage adult and pediatric patients and those with difficult airway.
2
Lungs’ separation vs. isolation
“Lung isolation” refers to complete anatomical shielding, mainly required to protect the healthy lung from contamination of pus, blood, or lavage fluids from the diseased lung, while “lung separation” describes surgical lung collapse to facilitate surgical access.
3
Double-lumen endobronchial tube (DLTs)
In different national and regional surveys, the double-lumen endobronchial tube (DLT) has been found to be used more frequently for lung separation or isolation tool than bronchial blockers (BB) [ ] because of the familiarity of anesthesiologists with their use and their lower cost compared with the BB. However, lately the use of BBs has been increasing in populations with anatomically smaller airways or multiple comorbidities [ ].
DLTs have a larger outer diameter, greater stiffness, and a pre-shaped angle. Their use has been associated with hoarseness, sore throat, mucosal, dental, and vocal cord injury, and injuries of the laryngeal cartilage or tracheobronchial tree [ , ].
There are trends in using more flexible brands, smaller sizes of the DLTs than the diameters of the targeted bronchus [ ], lower cuffs’ inflation pressures, video laryngoscopes (VLs) for DLT insertion, and DLTs with an embedded.
3.1
Techniques to minimize DLT-related complications
3.1.1
Systemic dexamethasone, topicalization of the DLT, and peripheral nerve block
Prophylactic use of dexamethasone 0.2 mg/kg [ ] and spraying the DLT with benzydamine hydrochloride [ ] can reduce the incidence of postoperative sore throat and hoarseness secondary to DLT intubation. Ultrasound-guided internal superior laryngeal nerve block reduces DLT-related sore throat [ ].
3.1.2
Sequential DLT rotation
Sequential rotation of a DLT over 180° facilitates its passage through the glottis and reduces the incidence of postoperative sore throat and vocal cord injuries [ ].
3.2
Selecting the appropriate size of DLT
Several anesthesiologists prefer using a small DLT (35F or 37F) because it is easy to place, fits all patients, and is not associated with an increased incidence of airway injury [ ]. Others prefer using a larger DLT (size of 39F and 41F) because a small DLT may require a high inflating bronchial cuff pressure to achieve lung isolation, render airway injury, increase the incidence of dislodgment, less effective bronchial suctioning, and increase airway resistance. There is no randomized clinical trial (RCT) that supports using either a small or a large DLT, the appropriate DLT size for each patient is thus based on either tracheal [ ] or left-main bronchial diameter [ Table 1 ] measured by computerized tomography ( CT ) scans or on the patient’s height and sex.
| Method | Size of Lef-side DLT |
|---|---|
| LMB Diameter in CT scan ( modified from Chow et al.) [ ] | |
| <11 mm | 35 Fr |
| 11–11.9 mm | 37 Fr |
| 12–12.9 mm | 39 Fr |
| >13 mm | 41 Fr |
| Transverse Diameter by Ultrasound and CT Multi-Planar Reconstruction (modified from Zhang et al.) [ ] | |
| The “average” transverse “outer” diameter (TD) of the cricoid cartilage (TD-C) measured by ultrasound | |
| <15.88 mm | 32 Fr |
| 15.88–16.80 mm | 35 Fr |
| 16.75–17.81 mm | 37 Fr |
| >17.80 mm | 39 Fr |
| Computed tomography (CT) measured the patient’s TD trachea in multi-planar reconstruction (MPR) | |
| <15.74 mm | 32 Fr |
| 15.74–16.65 mm | 35 Fr |
| 16.56–17.68 mm | 37 Fr |
| >17.65 mm | 39 Fr |
| Predictive Formulas for the Optimum Left-side DLT Depth | |
| Brodsky et al. [ ] | |
| The average insertion depth for male and female patients 170 cm tall was 29 cm, and for each 10 cm increase or decrease in height, the average placement depth was increased or decreased by 1 cm. | |
| Chow et al . [ ] | |
| Depth of insertion (cm) = 0.75 x clavicular-to-carinal distance of trachea (cm) + 0.112 x height (cm) + 6 with R(2) | |
| Liu et al. [ ] | |
| Marking the distance between the LDLT from the black line on the endobronchial lumen to the mouth side to the calculated distance between the vocal cord and carina using chest computed tomography (CT) | |
| El Dawlatly et al. [ ] | |
| 0.25 x body height (0.916) | |
Hannallah et al. [ ] developed a formula to predict the left bronchial diameter on the posteroanterior (PA) chest x-ray in men: diameter (mm) = 0.032 x age (year) + 0.072 x height (cm) −2.043.
Zhang et al. [ ] demonstrated that the proper size of a DLT can be derived by measuring the “average” transverse “outer” diameter of the cricoid cartilage (TD-C). This can be done by ultrasound using a linear 5–10 MHz probe that is placed perpendicularly to the neck just above the sternoclavicular junction in transverse section or also by CT [ Table 1 ].
3.3
Predicting DLT insertion depth
Optimally, the DLT endobronchial cuff should be placed just below the carina to decrease the incidence of obstructing the trachea, right upper lobar bronchus, and contralateral main bronchus. Several formulae suggested to predict the optimal DLT depth positioning have been validated [ Table 1 ]; however, a flexible fiber optic bronchoscope (FOB) remains mandatory to confirm the correct DLT insertion depth [ ].
3.4
Correct placement
Clinical evaluation confirming DLT placement and lung isolation by auscultation and observing chest movement is constantly inferior to FOB. FOB is the gold standard to confirm the correct DLT placement after intubation and after patient positioning (to exclude displacement). Concerns about a reusable FOB include infection risks, associated airway trauma, and equipment availability and cost [ ].
A systematic review and meta-analysis of 16 studies demonstrated that the total cost per use of a reusable and single-use FOB was £249 and £220 sterling, respectively in 2020. However, the cost of using the former per patient was £511 sterling due to infection treatment costs [ ].
The use of ultrasound has gained popularity because it allows safer and quicker confirmation of DLT positioning. A meta-analysis of 8 studies, including 771 patients, concluded that ultrasound had a similar sensitivity to clinical evaluation but higher specificity (0.61 vs. 0.35) and accuracy (78.6% 64.1%) [ ]. Ultrasound performance might be very close to FOB in identifying the correct position of the DLT and/or the need for re-adjustment [ ].
3.5
Flexible and softened DLTs
Silicone DLTs are softer and more flexible than the standard polyvinyl chloride (PVC) DLTs. Their use is associated with a lower incidence of postoperative sore throat, according to an RCT [ ]. A second RCT did not demonstrate similar results; however, silicone DLTs were easier and faster to place over the FOB and were associated with less airway trauma [ ].
Thermal softening of the PVC DLT can give the PVC DLT the same characteristics as the silicone DLTs’. The optimal temperature to facilitate FOB-guided placement while minimizing airway damage and avoiding thermal lesions is 40 ± 1 °C [ ]. It can significantly reduce the incidence of sore throat and vocal cord injuries but does not decrease the incidence of postoperative hoarseness [ ]. It is unclear if thermal softening might negatively impact the integrity of DLT tracheal and bronchial cuffs.
4
DLT with an embedded camera
A visualized DLT (VDLT) with an embedded video camera allows real-time visualization during DLT intubation and easily allows for corrective maneuvers in case of displacement, especially if access to the patient’s head is limited during the robotic surgery [ ].
VDLT reduces intubation time and the need for FOB to validate correct placement and is associated with fewer intraoperative misplacements [ ].
A propensity score-matched cohort analysis of 1780 patients demonstrated a lower incidence of hypoxemia using VDTL than the conventional DLT (3.6% vs. 6.5%). Still, it remains unclear whether this difference could be attributed to tube malposition or the patient’s comorbidities [ ].
The video-assisted endotracheal tube (ETT) can be combined with a BB, offering a continuous view of the BB placement and resulting in a shorter time to verify correct placement and lower peak airway pressures than VDLT or BB alone [ ].
VDLT is more expensive than conventional DLT. Cost-effectiveness studies pointed out a reduced need and costs both for the use of a single-use FOB use and the reusable FOB’s purchase, use, sterilization, and maintenance related costs [ , ].
5
Direct vs. video laryngoscopes for placements of DLT or BB
Using VLs with un-adjustable pre-shaped curves to place the bulky and rigid DLT may result in intubation difficulties.
A recent meta-analysis of 14 studies and 1310 patients comparing direct laryngoscopy with a Macintosh blade vs. VL found no difference regarding DLT intubation time but a higher first-pass successful intubation rate and a lower incidence of upper airway injury with the use of VL [ ].
5.1
Comparisons of different video laryngoscopes
Generally, DLT intubation is faster with the use of the channeled VLs with a conduit than non-channeled models [ ]. On the other hand, there is no difference in overall successful intubation, correct placement, or airway injury, regardless of the type of VL used [ ].
Table 2 summarizes the findings of the recent studies that compare direct laryngoscopes and different types of VLs for DLT intubation in terms of time to intubation, first-pass successful intubation, correct DLT placement, need for DLT adjustment after patient positioning, upper and lower airway injury, and postoperative sore throat.
| Video laryngoscope group | Reference | Study type | Intubation method | Number of patients | Airway | Objects | Outcomes |
|---|---|---|---|---|---|---|---|
| GlideScope® | Huang el al . (2020) [ ] | RCT | GlideScope® | 30 | Normal airway | Time to intubate(TTI), first-pass success (FPS) rate, numerical rating scales (NRS),Cormack-Lehane degrees (C/L), Intubation complications | The use of GlideScope® was associated with a longer time to intubate by 23 s(p = 0.003)T the Macintosh FPS rate was higher (p = 0.028). GlideScope® and C-MAC VL were associated with lower C/L degree and higher NIRS of DLT (p < 0.001). Comparable rates of complications related to intubation |
| C-MAC®(D) | 30 | ||||||
| Macintosh laryngoscope | 30 | ||||||
| Risse et al. (2020) [ ] | RCT | GlideScope® | 34 | Normal airway | TTI, other outcomes, complications related to intubation | The use of GlideScope® was associated with a longer time to intubate by 19 s (p = 0.044). In the GlideScope® group, bronchoscopic control revealed more frequent incorrect DTL positions (p = 0.041), endoscopic examinations revealed a higher rate of red-blooded vocal cords, vocal cord hematoma, and hemorrhage (p < 0.05). | |
| Macintosh laryngoscope | 31 | ||||||
| McGrath MAC | Bakshi et al. (2019) [ ] | RCT | McGrath MAC | 37 | Normal airway | TTI, conditions related to intubation, complications of intubation | Time to successful intubation was comparable. Use of McGrath MAC VL was associated with more frequent CL grade I (p = 0.007), reduced need for ELM (p = 0.013), and fewer complications (p = 0.013). |
| Macintosh laryngoscope | 36 | ||||||
| Yoo et al. (2018) [ ] a | RCT | McGrath MAC | 22 | Simulated difficult airways | TTI, conditions related to intubation, need for external laryngeal manipulation (ELM), other outcomes, complications related to intubation | Time to successful intubation was comparable. Use of The McGrath VL was associated with lower C/L grade (p < 0.001), decreased need for ELM (p < 0.001), and resulted in a lower overall intubation difficulty scale score (p < 0.001) in patients with in-line stabilization. | |
| Macintosh laryngoscope | 22 | ||||||
| C-MAC D-blade VL | Kim et al. (2022) [ ] | RCT | C-MAC D-blade VL | 47 | Normal airway | TTI, conditions related to intubation | Time to successful intubation was comparable. Use of C-MAC D-blade VL was associated with lower C/L degree(p = 0.00), better glottic opening (p = 0.00) a and lower intubation difficulty scale score(p = 0.03) |
| McCoy laryngoscope | 43 | ||||||
| Mathew et al. (2022) [ ] | RCT | C-MAC D-blade VL | 36 | Normal airway | time to visualization of the glottis, TTI, conditions related to intubation, complications related to intubation | C-MAC D-blade VL was associated with faster visualization of the glottis by 2.71s (p = 0.01). Time to intubation was comparable. In the C-MAC D-blade VL group, patients were better laryngoscopic grade (p = 0.007), lower intubation difficulty scores (p = 0.046), and needed less ELM (P = 0.0430) | |
| Macintosh laryngoscope | 37 | ||||||
| Airtraq DL™ | Mounika et al. (2022) [ ] a | RCT | Airtraq DL™ | 25 | Simulated difficult airways | TTI, conditions related to intubation, incidence of complications, other outcomes | The use of Airtraq DL ™ was associated with a shorter time to intubate by 7,48 s (p = 0.003), better C/L grading (p ≤ 0.001), a lesser requirement of maneuvers (p = 0.02) and lower IDS (p = 0.003) |
| Macintosh laryngoscope | 25 | ||||||
| Feng et al. (2020) [ ] | RCT | Airtraq DL™ | 31 | Normal airway | the EC50 of remifentanil for inhibiting cardiovascular responses to DLT intubation, time to intubate, intubation conditions | Intubation by Aitraq was longer by 9s (p = 0.001). Aitraq provided more C/L grade views (29/31 vs 17/31, p = 0.002). | |
| Macintosh laryngoscope | 31 | ||||||
| El Tahan et al. (2018) [ ] a | RCT | Airtraq DL™ | 35 | Easy and difficult airway | time to successful DLT intubation, intubation conditions, complications related to intubation, other outcomes | The use of Airtraq was associated with a shorter time to successful intubation by 36,6 s(p = 0,021) and a lower score for difficult intubations (p = 0.023) compared with Glidescope and the shorter time of laryngoscopy Compared with the other three devices tested (p = 0.003) | |
| GlideScope® | 34 | ||||||
| KVL | 32 | ||||||
| Macintosh laryngoscope | 32 | ||||||
| Ajimi et al. (2018) [ ] | RCT | Airtraq DL™ | 30 | Normal airway | TTI, complications at intubation, other outcomes | The use of Airtraq DLTM was associated with a shorter time to intubate by 4,1s (p = 0.005) | |
| AWS-200 | 30 | ||||||
| Video stylet | Gu et al. (2023) [ ] | RCT | Rigid Video Stylet (RVS) | 61 | Normal airway | TTI, first-attempt success rate, complications related to intubation | The use of RVS was associated with a shorter time to intubate by 8,8s (p < 0.001) and a lower FPS rate (p = 0.048) |
| Macintosh laryngoscope | 63 | ||||||
| Chang et al. (2018) [ ] | RCT | Lighted stylet | 32 | Normal airway | TTI, other outcomes, postoperative complications related to intubation | The use of the Lighted style was associated with reduced intubation time by 15 s (p < 0.001) and easier advancement of DTL toward the glottis (p > 0.001) | |
| GlideScope® | 31 |
6
The world of bronchial blockers
6.1
Which blocker is better?
No solid evidence supports using one BB over the other. Most meta-analyses compared DLTs and BBs rather than different BB types.
A meta-analysis including 495 patients from 6 RCTs [ ] demonstrated faster placement, less frequent displacement, and a greater incidence of throat soreness when using the left-side DLTs instead of the EZ blocker. Other than that, both tools had a comparative surgeons-rated quality of lung collapse and a similar incidence of carinal trauma and post-extubation hoarseness. The vast differences in diameters between the EZ blockers and DLTs would impact the speed of lung deflation, in favor of DLTs [ ].
6.2
Features, technical tips, and concerns
Rispoli et al. [ ] compared the design features of the commonly commercially available blockers [ Table 3 ].
| Bronchial Blocker | Size (Fr) | Length (cm) | Cuff Shape | Cuff Pressure | Cuff volume (ml) | Cuff Auto-inflation | Recommended ETT size (mm) | Internal diameter (mm) | |
|---|---|---|---|---|---|---|---|---|---|
| Spherical cuff | Elliptical cuff | ||||||||
| Fogarty (Edwards) b | 4 | 40 to 80 | High | 1.7 | 4.0 | ||||
| 5 | 80 | High | 3.0 | 4.5 | |||||
| 7 | 80 | High | 5.0 | 6.0 | |||||
| Arndt (Cook) b | 5 | 50 | + | Low | 0.5 to 2 | 4.5 to 5.5 | 0.7 | ||
| 7 | 65 | + | Low | 2 to 6 | 6.0 to 7.5 | 1.4 | |||
| 9 | 78 | + | Unavailable since 2010 | Low | 4 to 8 | 7.5 to 8.0 | 1.4 | ||
| Cohen (Cook) b | 9 | 65 | + | Low | 6 to 9 | 7.5 to 8.0 | 1.6 | ||
| Low | |||||||||
| Endobronchial blocker (Tappa Medical) a | 5 | 45 ± 5 | + | Low | 2.0 | + | 4.5 to 5.5 | 1.0 ± 0.2 | |
| 7 | 55 ± 5 | + | Low | 3.0 | + | 6.0 to 7.0 | 1.6 ± 0.3 | ||
| 9 | 55 ± 5 | + | Low | 4.5 | + | 7.5 to 8.5 | 2.5 ± 0.3 | ||
| Coopdech (Daiken Medical) b | 9 (=3.0 mm) | 60 | Small spindle-shaped | Low | 4.6 | + | 7.5 to 8.0 | ||
| 9 (=3.0 mm) | 60 | Rectangular round- shaped | Low | 7.5 | + | 7.5 to 8.0 | 1.2 | ||
| Fuggiano blocker (Fuji) | 9 | 66.5 | + | Low | 5.0 | 7.5 to 8.0 | 2 | ||
| Uniblocker (Fuii) b | 5 | 32.5 | + | Low | 3.0 | 4.5 to 5.5 | No inner channel | ||
| 9 | 50 | + | Low | 8.0 | 7.5 to 8.0 | 2 | |||
| EZ-Blocker (Teleflex) b | 7 | 75 | + | Low | Left side: 6.7 ± 1.16 Right side: 8.0 ± 1.1 | 7.0 | 2.33 mm for the main catheter 1.17 mm for each limb | ||
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