Abstract
For many thoracic operations lung separation to enable collapse of the operated lung is either necessary or useful for successful surgery. Lung separation may also be required in other settings for management of pulmonary bleeding, infection or complicated lung ventilation. Lung separation requires knowledge, skill and attention to detail. New technology including videolaryngoscopy, tracheal tubes incorporating distal cameras and improvements in bronchial blocker technology have added to the anaesthetist’s armamentarium. This chapter describes the indications, techniques and complications of lung separation of relevance to generalist and specialist anaesthestists.
Introduction
The modern practice of thoracic surgery depends on the anaesthetist’s ability to collapse and selectively ventilate the lungs. Selective lung collapse facilitates surgical exposure, while anatomical isolation protects the non-operated lung from contamination. Lung isolation and selective collapse are achieved with either a bronchial blocker (BB) or a double-lumen tube (DLT).
Bronchial Blocker (BB)
Lung tissue distal to an obstructed conducting airway will collapse. Modern BBs are thin semi-rigid plastic catheters with a high-volume low-pressure balloon at their distal tip. When inflated the balloon obstructs the airway. Many BBs have an inner channel that can be opened to hasten lung deflation. The channel can be used to suction the lung and for application of continuous positive airway pressure (CPAP).
A BB is introduced under visual guidance using a flexible optical bronchoscope (FOB) alongside or through a tracheal tube (TT), tracheostomy tube or supraglottic airway, into a bronchus. The ETView VivaSight SL (Ambu, Copenhagen, Denmark) is a new TT with an integrated high-resolution imaging camera. Using a BB with this tube does not require an additional endoscope. A three-way connector allows both the BB and FOB to be advanced simultaneously without interrupting ventilation (Figure 27.1).
Figure 27.1 A bronchial blocker (BB) is introduced into the airway either alongside or within the lumen of a standard tracheal tube or supraglottic airway. A special three-port connector allows advancement of both the BB and a paediatric flexible optical bronchoscope (FOB) without interfering with ventilation. The FOB allows direct visualisation of BB placement.
A variety of independent BBs are available (Figure 27.2).
The Fuji Uniblocker (Teleflex, Wayne, PA, USA) has an angulated distal tip. Digital rotation at the catheter’s proximal end directs the tip into either bronchus.
The Cohen Flexitip Endobronchial Blocker (Cook Critical Care, Bloomington, IN, USA) uses a rotational wheel at the operator’s end to mechanically manoeuvre the distal tip into position.
The Arndt Endobronchial Blocker (Cook Critical Care) has a wire loop in its central channel. The loop is snared over an FOB, which is then advanced into a bronchus. The loop with the BB is slid over the bronchoscope directly into the bronchus. Once in position, the FOB is removed and the wire is withdrawn into the catheter’s lumen.
The EZ-Blocker (AnaesthetIQ BV, Rotterdam, the Netherlands) has a distal end that splits into two 4-cm-long extensions, each with its own balloon. The extensions are symmetrical, with one balloon dyed blue and the other yellow for identification. The EZ-Blocker is advanced into the trachea under FOB control until the Y engages the carina preventing further advancement. Either balloon can then be inflated as required. When correctly positioned each extension will be in a main-stem bronchus, so either lung can be collapsed. An EZ-Blocker can be placed ‘blindly’ if necessary.
A unique approach to bronchial blockade is the Papworth BiVent Tube (P3 Medical Limited, Bristol, UK). It is a single-cuffed DLT with a bifurcated distal end to ‘blindly’ engage the carina with each lumen opening into one main bronchus. A BB can be advanced down either lumen into the desired bronchus for rapid lung isolation without the need for FOB guidance.
Double-Lumen Tube (DLT)
A DLT consists of two tubes of unequal length moulded together (Figure 27.3). The shorter tube ends in the trachea and the longer tube ends in a main-stem bronchus. There is a cuff above the opening of the shorter ‘tracheal lumen’ and a second cuff above the distal opening on the ‘bronchial lumen’. Proximally the two tubes have their own connectors to attach to a dual lumen catheter mount (Figure 27.3). Adult sizes are 41 Fr, 39 Fr, 37 Fr and 35 Fr.
Inflating only the tracheal cuff enables positive pressure ventilation to both lungs. Inflating both cuffs enables both lungs to be ventilated separately: clamping one of the lumens of the catheter mount will stop ventilation to that lung, while ventilation can continue to the other lung. If the catheter mount tubing to the non-ventilated lung is then detached that lung will collapse.
Figure 27.3 Double-lumen tubes (DLTs) consist of two tubes of unequal length moulded together. The shorter tube ends in the trachea and the longer tube in a main bronchus. There is a proximal cuff on the tracheal portion and a distal cuff on the bronchial lumen. Inflating the tracheal cuff allows positive pressure ventilation to both lungs. When both the bronchial and tracheal cuffs are inflated, the lungs can be ventilated together or separately. Selectively clamping the lumen to either lung at a connector at the proximal end of the DLT enables separation and collapse of that lung, while ventilation continues through the unclamped lumen to the other lung.
DLTs are constructed of clear plastic, which enables observation of condensation, blood or purulent material coming from the lungs. Suction catheters or a paediatric FOB can be passed down either lumen. The bronchial cuff is usually dyed blue for easy visual identification.
Human airway anatomy is asymmetric. The left main bronchus is longer (average 5.4 cm males, 5.0 cm females) than the right main bronchus (average 2.3 cm males, 2.1 cm females). In as many as 10% of adults the right upper-lobe bronchus originates at the carina or even in the trachea. DLTs are designed for intubation of either the left or the right bronchus. Either tube can be used to isolate either lung, but a left DLT is usually preferred. A left DLT has a greater ‘margin of safety’ since there is less chance of it obstructing the ipsilateral upper-lobe bronchus. Right DLTs have an additional slot in the bronchial lumen wall to reduce the risk of obstructing the upper-lobe orifice. Right DLTs are used when placement of a left DLT is impractical or unsafe.
Selecting a DLT based on height and gender has a poor correlation with actual airway size. The width of the left bronchus and/or trachea can be measured from the patient’s chest radiograph or CT scan. Left main bronchial width can be accurately estimated from tracheal width using the formula:
If the dimensions of the DLT and left bronchus are known an appropriate size left DLT can be chosen for that patient.
A large DLT is preferred for several reasons:
There is less resistance to airflow during one-lung ventilation through a larger lumen and less chance of developing auto-PEEP (positive end-expiratory pressure) and air trapping in patients with chronic obstructive pulmonary disease.
A larger lumen more easily accommodates an FOB or suction catheter.
Larger DLTs cannot be advanced as far into the airway as smaller tubes, reducing the chance of malpositioning.
The bronchial cuff of a large DLT requires less air to seal the bronchus, which in turn may reduce the risk of trauma from overinflation.
A DLT can be placed by clinical examination and auscultation, followed by bronchoscopy to confirm or adjust position. Alternatively, a DLT can be directly guided into the intended bronchus using an FOB. The VivaSight DL DLT (Ambu, Copenhagen, Denmark) has an integrated high-resolution camera which enables faster insertion and initial positioning and reduces or eliminates the need for an FOB. It provides continuous visual monitoring throughout the procedure, so malposition and dislocation are easily detected by real-time high-resolution video images transmitted to a monitor.
Familiarity with the clinical signs for DLT placement is important since a clean, functioning FOB may not always be available. An FOB may also be too large for smaller DLTs, and blood or mucus in the airway can interfere with the ability to identify the carina or the blue bronchial cuff.
Since a left DLT is used most often, the steps for left DLT placement are described.
Following successful laryngoscopy, the blue bronchial cuff is passed just past the vocal cords. Before advancing the tube further the stylet in the bronchial lumen is withdrawn. The DLT is then rotated 90°–120° anticlockwise until its tip is directed towards the left and advanced down the airway. The former recommendation was to advance a DLT until moderate resistance was encountered. With thin plastic DLTs this practice will often result in the tube being inserted too deeply. For both men and women, the depth of placement for a left DLT is highly correlated with height, and can be expressed by the formula:
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