Conference Lectures

LUNG ISOLATION TECHNIQUES
Dr. Rajeev Ranjan, senior consultant, MedantaTheMedicity,                 Gurgaon, India
INTRODUCTION
Lung isolation techniques refer to mechanical separation of the two lungs to allow ventilation of only one lung, while the other lung is compressed by the surgeon or allowed to passively deflate.
INDICATIONS
 For better surgical area exposure as in minimally invasive cardiac, thoracic, mediastinal, descending aortic,esophagealor chest wall.
Lung isolation is also used to protect the lung from soiling by the contralateral lung (bronchopleural fistula, pulmonary hemorrhage).
To provide differential patterns of lung ventilation in cases of unilateral reperfusion injury (after lung transplantation or pulmonary thromboendarterectomy) or in unilateral lung trauma and positive end expiratory pressure ventilation1
ANATOMY OF TRACEOBRONCHUS:
The trachea is nearly but not quite cylindrical, flattened posteriorly. In cross-section, it is D-shaped, with incomplete cartilaginous rings anteriorly and laterally, and a straight membranous wall posteriorly. The trachea is, on average 15 cm long and is chondromembranous. This structure starts from the inferior part of the larynx (cricoid cartilage) in the neck, opposite the 6th cervical vertebra, to the intervertebral disc between T4-5 vertebrae in the thorax, where it divides at the carina into the right and left bronchi.(yale radiology). The trachea is having C shaped cartilages which isdeficient posteriorly.


The average diameter in a normal trachea is 22 mm in men and 19 mm in women.In men, the coronal diameter ranges from 13 to 25 mm and the sagittal diameterranges from 13 to 27 mm. In women, the average coronal diameter is 10–21 mmand the sagittal diameter is 10–23 mm.2-3The cricoid cartilage is the narrowest part of the trachea with an average diameterof 17 mm in men and 13 mm in women. The trachea bifurcates at the carina intothe right and left mainstem bronchus. An important fact is that the tracheal lumennarrows slightly as it progresses towards the carina. The tracheal bifurcation islocated at the level of the sternal angle anteriorly and the 5th thoracic vertebra posteriorly.
In men, the distance from the tracheal carina to the take-off of the right upper lobebronchus is an average of 2.0 cm, whereas it is approximately 1.5 cm in women. The diameter of the right mainstem bronchus is an average of 17.5 mm in men and 14 mm in women. The trifurcation of the right upper lobe bronchus consists of the apical, anterior, and posterior division. This is a very important landmark to identify while performing fiberoptic bronchoscopy in order to distinguish the right from the left mainstem bronchus.4
The distance from the tracheal carina to the bifurcation of the left upper and left lower lobe is approximately 5.0 cm in men and 4.5 cm in women.

OPTIONS FOR LUNG ISOLATION

1. Double Lumen Technology (Left and Right-Sided double lumen
endotracheal tubes)
2. Bronchial Blocking Technology. This involves blockade by the brochialblockers of a mainstem bronchus to allow lung collapse distal to the occlusion.
Double lumen technology.
The first DLT was designed by Carlens’ in the 1950s which was having a carinal hook. In the 1960s Robertshaw modified this design, by introducing DLTs without carinal hooks, larger lumens and left and right DLTs.
Lung isolation is most commonly achieved with a double lumen tube (DLT). TheDLT is a bifurcated tube with both an endotracheal and an endobronchial lumenand can be used to achieve isolation of either right or the left lung.10
All DLTs share the following characteristics:
1. A longer bronchial lumen that enters either the right or left main bronchus and another shorter tracheal lumen that remains in the lower trachea.
2. A preformed curve that allows preferential entry into either bronchus.
3. A bronchial cuff.
4. A tracheal cuff.
Ventilation can be delivered to only one lung by clamping either the bronchial or tracheal lumen with both cuffs inflated; opening the port on the appropriate connector allows the ipsilateral lung to collapse.
Left and right sided DLTs are available to pass into the left and right bronchus respectively. This is due to the difference in anatomy between the two main bronchi. Left DLTs are used more frequently than right DLTs.
In an article describing their clinical experience of Left DLTs in 1170 patients, Brodsky and Lemmens13 prefer a L DLT for both right- and left-sided procedures. This is because that the right bronchus is much shorter than the left bronchus so there is a greater risk of upper-lobe obstruction with a right D

Table 1: comparative diameter of SLT & DLT


Single lumen tubes

Double lumen tubes

Internal diameter(mm)

external diameter(mm)

French size(Fr)

External diameter(mm)

Bronchial Internal diameter(mm)

FOB size(mm)

6.5

8.9

26

8.7

3.2

2.4

7.0

9.5

28

9.3

3.4

2.4

8.0

10.8

32

10.7

3.5

2.4

8.5

11.4

35

11.7

4.3

>3.5

9.0

12.1

37

12.3

4.5

>3.5

9.5

12.8

39

13.0

4.9

>3.5

10

13.5

41

13.7

5.4

>3.5

 

 LEFT SIDED DOUBLE LUMEN TUBE
1.  A properly sized DLT is one in which the main body of the tube passes without resistance through the glottis and advances easily within the trachea, and in which the bronchial component passes into the intended bronchus without difficulty.10
2. The bronchial cuff should be able to seal properly just after adequately inflation. DLT is chosen on the basis of: (A) patient height and gender.(table 2)
Table: 2


Sex

Height(cm)

Size(Fr)

female

< 160

35

Female

>160

37

Male

<170

39

Male

>170

41

 

(B) On the basis of tracheal diameter inCXR.
A later study by Brodksyet al8suggested a more accurate method for selecting Left DLTs based on the tracheal diameter. They found a significant correlation between tracheal size and bronchial diameter. Using a ratio of left bronchial diameter to tracheal diameter of 0.68, the bronchial width could thus be calculated from the measured tracheal width. They devised a guide to choose the correct Left DLT by measuring the tracheal width at the level of the clavicles on a pre-op
P-A CXR.(table 3)
Table 3 -- Guidelines for Choice of Left DLTs


Measured tracheal width(mm)

Predicted left bronchus width(mm)

DLT size

Outside diameter(mm)

Inside diameter(mm)

>/=18

>/=12.2

41 Fr

14-15

10.6

>/=16

>/=10.9

39 Fr

13-14

10.1

>/=15

>/=10.2

37Fr

13-14

10.0

</=14

</=9.5

35Fr

12-13

9.5

METHODS OF PLACEMENT OF LEFT-SIDED DLT 1,6,7
There are 2 recognised methods for placement of the left sided DLT
1. Blind Method:
A left DLT is passed by direct laryngoscopy beyond the vocal cords with a stylet in place(endobronchial lumen), the stylet is then withdrawn and the tube rotated 90° counterclockwise and advanced until slight resistance is felt, which usually indicates that the endobronchial lumen of the DLT has entered the bronchus adequately.

Figure: The blind method technique for placing a left-sided DLT
A: The DLT is passed with direct laryngoscopy beyond the vocal cords.B: The DLT is rotated 90 degrees to the left.C: The DLT is advanced until moderate resistance is felt, indicating that the endobronchiallumen of the DLT has entered the bronchus
(in general 27 cm marks the level of the teeth). SAJAA 2008; 14(1): 22-26

Fibreoptic-Directed Method:
The  left DLT is passed just beyond the vocal cords by direct laryngoscopy. Once the endobronchial tipof the DLT has passed the vocal cords, the fibrescope is passed down the endobronchial lumen, and the tip of the DLT is then guided over the fibrescopeinto the left main bronchus.

 

Figure 6: The FOB guidance technique for placing a left-sided DLT
A: The DLT is passed with direct laryngoscopy beyond the vocal cords.B: The fibreoptic bronchoscope is advanced through the endobronchiallumen.The tracheal carina and left mainstem bronchusare visualised.C: The DLT is rotated 90 degrees to the left and, with the aid of the fibreoptic bronchoscope, the tube is advanced into the leftmainstembronchus.SAJAA 2008; 14(1): 22-26

 

Auscultation followed by fibreoptic bronchoscopy are current methods to confirm DLT placement. Full inflation of both the endotracheal and endobronchial cuffs arerequired to achieve a good seal.No leaks should be present with a maximum of 3ml air in endobronchial cuff.
It is crucial to recheck the position of the tube once the patient is re-positioned as it is often found that the turning the patient lateral results in apparent movement of the tube more proximal into the trachea. Auscultation alone is unreliable for proper DLT placement.
The use of fibreoptic bronchoscopy has several benefits, which include, being able to confirm and correct malpositioned tubes, detect airway injuries, suction and jet ventilate through the available ports.
However, fibreoptic bronchoscopy can only be beneficial in experienced hands. In a study involving anaesthetists with limited experience in lung isolation techniques, it was found that although fibreoptic bronchoscopy was used to place the devices, malpositions were not recognised in up to 38% of cases. Possible reasons for this were lack of skill with fibreoptic bronchoscopy and lack of the recognition of the airway anatomy.
RIGHT-SIDED DOUBLE LUMEN ENDOTRACHEAL TUBES1,6,7
Although the left-sided DLT is used for lung isolation in most cases due to the greater margin of safety it provides, the right sided DLT is recommended in certain situations.
Recommendations for a Right-Sided DLT:
- Distorted anatomy at the entrance of left mainstem bronchus by an
intrabronchial or external compression.
- Compression at the entrance of the left mainstem bronchus due to a
descending thoracic aortic aneurysm.
- Left –sidedpneumonectomy.
- Left-sided single-lung transplantation.
- Left-sided sleeve resection.
- Any contra-indication to place a left-sided DLT.
The Right Sided DLT is placed under fibre-optic guidance, the optimal position
being, one that provides good alignment between the opening slot of the
endobronchial lumen and the right upper lobe bronchus and distally a clear view
of the bronchus intermedius and the right lower lobe bronchus seen from the
endobronchial lumen. The fibre-optic view through the endotracheal lumen would show a clear view of the left mainstem bronchus, and the edge of the fully inflated endobronchial cuff below the tracheal carina in the right bronchus. A rotational movement might aid alignment of the slot of the tube with the right upper lobe bronchus.
COMPLICATIONS OF DOUBLE LUMEN TUBE PLACEMENT5
Malposition:
Causes of malposition include, an overinflated cuff, extension of head and neck in the lateral decubitus position and surgical manipulation of the bronchus. Fibreoptic bronchoscopy is the recommended method to correct intra-operative malpositions.
Airway Trauma:
Airway trauma can present as an unexpectedpostoperative hoarseness and sore throat to unexpected air leak, subcutaneous emphysema, massive airway bleeding into the lumen of the DLT, or protrusion of the endobronchial or endotracheal cuffs into the surgical field. In these instances, bronchoscopy and surgical repair is indicated.

 

BRONCHIAL BLOCKERS
Bronchial blocker was introduced by Magill in1936. Later on a number of modifications led to the development of present day blockers.
These devices can be used independently by passing it within the lumen of conventional single lumen tube, these are;
• Arndt wire- guided endobrochial blocker
• Cohen tip-deflecting endobronchial blocker
• Fuji Uniblocker
• Fogarty venous embolectomy catheter
Sometimes incorporated within a modified single lumen tube:
• torque control blocker (Univent)

 

For standard adult 9Fr blockers, an ETT >/= 7.0mm ID can be used with a bronchoscope <4.0mm in diameter. Larger bronchoscopes will require an ETT >7.5mmID.
Bronclial blockers are equally competent device for lung isolation and preferred over DLT in situations like:
Specific indications for Bronchial blockers7
- difficult airways                  
- limited mouth opening
- Nasotracheal intubation         
- awakeorotracheal intubation
- selective lobar blockade       
- already intubated patient requiring lung isolation
- potential for mechanical ventilation in the post op period
CPAP can be applied through several bronchial blockers, as well. Additionally, bronchial blockers can provide selective blockade of a specific lobe. This is particularly useful in the patient with an isolated air leak, hemorrhage, or infection in one lobe, thereby allowing ventilation of more lung units.

THE ARNDT®BLOCKER9,10
The Arndt®Blocker, a wire-guided endobronchial blocker is an independent
blocker that is passed through an existing SLT. The spherical shaped blocker is used for right sided mainstem bronchial intubation whilst the elliptical shaped blocker is for intubation of the left mainstem bronchus. For ease of insertion through the endotracheal tube, the blocker and the fibre-optic bronchoscope are lubricated.
The placement of the Arndt Blocker involves placing the endobronchial blocker through the endotracheal tube and using the fibre-optic bronchoscope and wire guide to direct the blocker into a mainstem bronchus. The fibreoptic bronchoscope has to be advanced distally enough so that the Arndt®blocker so that enters the bronchus while it is being advanced. When the deflated cuff is beyond the entrance of the bronchus, the scope is withdrawn, and the cuff fully inflated with 4-8ml of air under fibre-optic view to obtain total bronchial blockade.                                                       
Optimal position of the Arndt blocker in the left or right bronchus is achieved when the proximal edge of the fully inflated cuff is approximately 5-10mm below the trachea carina.
Placement of the blocker into the right mainstem bronchus can be performed without the wire loop under fibre-optic visualisation.
It is important to remove the wire loop to avoid inclusion in the stapling line of the bronchus.

COHEN®ENDOBRONCHIAL BLOCKER9,10
Used for tip-deflecting, wire-guided endobronchial blockade of the left or right lungfor procedures which require one-lung ventilation. Balloon is low-pressure, high volume. A manually torqued device with a high-traction silicon grip on the introducer shaft for precise placement into the desired airway.
The unique deflecting tip provides a wide range of adjustments to precisely direct the blocker under bronchoscopic guidance. An indicator arrow on the turning wheel shows which direction the tip deflects, ensuring fail-safe access to the desired lung.
Optimal placement in the left mainstem bronchus is when blocker balloon’s outer surface is seen with fibreoptic bronchoscope at least 5mm below the trachea carina inside the left mainstem bronchus.

FUJI UNIBLOCKER®
The FUJI uniblocker, once lubricated is passed through the single lumen
endotracheal tube. Its distal end is angulated to facilitate insertion under fibreoptic guidance into the desired main-stem bronchus. Optimal position of the fully  inflated cuff(4-8ml of air), as seen with fibre-optic bronchoscope is at least 5-10mm below the tracheal carina inside left main-stem bronchus and at least 5mm below the tracheal carina on the right main-stem bronchus.

FOGARTY EMBOLECTOMY CATHETER AS BRONCHIAL BLOCKER9
The Fogarty embolectomy catheter, a device used in vascular surgery can also be used to provide lung isolation. The occlusion balloon of the Fogarty catheter is considered to high pressure, low volume, requires 0.5-10ml of air to achieve bronchial occlusion. The catheter also has a stylet which can be used to mould the distal end of the catheter prior to insertion.
Although the Fogarty catheter can provide reliable lung isolation especially as a rescue device when passed through a DLT that cannot be properly positioned, it has several disadvantages. It is designed to be a vascular device, not a bronchial blocker, it has no channel for suction or jet ventilation, an air leak from the breathing circuit is common.

 

TORQUE CONTROL BLOCKER (UNIVENT) 9
This brochial blocker is enclosed into a single lumen endotracheal tube-the original Univent®. Within the Univent®unit there is a channel enclosing a moveable brochial blocker that can be used to block the left, right or any specific bronchi. Before use, both the bronchial blocker and the endotrachial cuff are lubricated for ease of insertion. The enclosed bronchial blocker is retracted into the standard lumen of the tube. Once conventional tracheal intubation is performed, a fibreoptic bronchoscope is passed and the enclosed bronchial blocker is directed into the bronchus to be isolated. Advantages of this device is its use to achieve lung isolation in patients with difficult airways.

COMPLICATIONS RELATED TO BRONCHIAL BLOCKERS5
• Inclusion of the bronchial blocker or the distal wire loop of the Arndt Blocker into the stapling line: the device should be pulled back a few centimetres before the stapling.
• movement of the bronchial blocker from the bronchus into the trachea which can lead to failure to ventilate and hypoxia.

CONCLUSION
Anaesthesiologists are frequently requested to provide lung isolation. Lung isolation is indicated most commonly, for surgical exposure, to protect a contralateral lung from contamination by bleeding or pus and to provide differential lung ventilation. There are multiple lung isolation devices available, each with advantages and disadvantages. It is the responsibility of the anaesthesiologists to have knowledge of the tracheobronchial anatomy with recognition of the anatomy on pre-operative chest radiograph, be familiar with the available lung isolation devices and be skilled in performing fibre-optic bronchoscopy. These factors have proved to increase the chance of successful lung isolation.
REFERENCES
1. Campos JH. Current techniques for peri-operative lung isolation in adults.
Anaesthesiology 2002;97:1295-1301
2. Boiselle PM. Imaging of the large airways. Clin Chest Med 2008;29 181-193
3. Seymour AH. The relationship between the diameters of the adult cricoids
ring and main tracheobronchial tree: a cadaver study to investigate the basis
for double-lumen tube selection.JCardiothoracVascAnaesth 2003;17:299-
301
4. Campos JH. Update on tracheobronchial anatomy and flexible fibreoptic
bronchoscopy in thoracic anaesthesia.CurrOpin Anaesthesiology 2009;22:4-
10
5. Ronald D. Miller et al Miller’s Anaesthesia 7th Edition 1833-1841
6. Brodsky JB, Lemmens HJ. Left Double Lumen Tubes: Clinical Experience
with 1,170 patients. J CardiothoracVascAnesth. 2003 Jun;17(3):289-98
7. Campos JH. Update on lung separation techniques: Double-lumen tubes and
bronchial blockers. ConferenciasMagistrales. Vol 34.Supl. 1 Abril-Junio
2011 pp S270-S277
8. Brodsky JB, Macario A. Mark JBD. Tracheal diameter Predicts Double-Lumen
Tube Size: A Method for selecting Left Double Lumen Tubes. AnesthAnalg
1996;82:861-4
9. Campos JH. An Update on Bronchial Blockers During Lung Separation
Techniques in Adults.AnesthAnalg 2003;97:1266-74
10. Cook® Medical Website product information.