Every anesthesiologist should be able to isolate and collapse a lung when requested to do so. The methods currently used to accomplish this are blockade with a bronchial blocker (BB) or by endobronchial intubation with a double-cuffed, double-lumen tube (DLT). A BB is advanced alongside or through an endotracheal tube (ETT) into the bronchus of the lung, and when the blocker’s balloon is inflated, lung tissue distal to the obstruction will collapse. Since a BB can be used once an ETT is in place, it is a good option for a patient with a “difficult airway” and in pediatric patients too small for the smallest DLT. However, for most patients a DLT offers many more advantages than a BB (Table 22-1). This chapter will discuss the use of DLTs for separation of the lungs.

Table 22-1
Advantages of DLTs

The first rubber DLTs (1950s) were difficult to position. The introduction of the plastic DLTs (1980s) coupled with the intraoperative use of fiberoptic bronchoscopes (FOBs) improved the safety and reliability of DLT placement, although the potential for airway trauma still exists (Table 22-2) (1).

Table 22-2
Risk Factors for Airway Rupture with DLTs

Clinical Signs for Placement of DLT

This chapter will focus on the use of clinical signs for DLT placement. Why not just use a FOB from the start? I believe it is essential to be familiar with other methods. A clean, functioning FOB may not always be available, especially during an emergency. Should the case then be delayed or cancelled? Many pediatric FOBs are too large for small DLTs. Blood or mucus can obstruct the endoscopist’s ability to identify the carina or visualize the blue bronchial cuff. A FOB remains an extremely useful adjunct for confirmation of DLT placement, especially for residents in training and for clinicians who use a DLT infrequently. As one gains experience with clinical DLT placement there is less need for absolute reliance on a FOB (2).

The clear plastic material of disposable DLTs allows observation of moisture during ventilation and/or the presence of secretions or blood in either lumen. The blue bronchial cuff is easily visualized with a FOB. The high volume/low pressure bronchial cuffs reduce the danger of ischemic pressure damage to airway, and the large lumens allow easy passage of a FOB or suction catheter with less resistance to gas flow during one-lung ventilation (OLV) (3).

Selection of DLT

A right- or a left-DLT can be used for either a right or a left thoracic procedure (4), but the “margin of safety” is greater with a left-DLT (5). Human airways are asymmetric; the right bronchus is very short (average 2.3 cm in males, average 2.1 cm in females) compared to the left bronchus (average 5.4 cm in males, average 5.0 cm in females). There is a greater risk of malposition with a right-DLT. As many as 10% of normal adults have a carinal or even tracheal origin of their right upper-lobe bronchus, so correct placement of a right-DLT is even more difficult in these patients. Therefore, unless contraindicated, a left-DLT should always be chosen. A right-DLT is indicated when a left-DLT cannot be used, as with obstruction of the proximal left-main bronchus or when placement would interfere with the planned surgical procedure (Table 22-3).

Table 22-3
Indications for Right DLTs

It is important to select the largest DLT that can be atraumatically introduced into the left bronchus (6). A large DLT cannot be advanced as far as a thinner one so there is less chance of left upper-lobe obstruction when a larger tube is used. In addition, the bronchial cuff requires less air to seal the airway reducing the risk of trauma from overinflation. Larger internal lumens offer less resistance to airflow during OLV so less auto-PEEP develops (Table 22-4).

Although some select DLT size based on patient height and gender—tall men get larger tubes, small women get smaller tubes—this method is relatively inaccurate since bronchial diameter is not proportional to height or gender (7). Prior to intubation left bronchial width or tracheal width should be measured from the patient’s chest radiograph or chest CT scan. Although average tracheal diameter varies (average 20.6 mm, range 16.0 to 29.0 mm for men, average 17.0 mm, range 13.0 to 22.0 mm for women), the diameter of the left bronchus is directly proportional (~70%) to tracheal diameter (8). Therefore, if tracheal width is known then left bronchial width can be estimated and an appropriate (large) DLT selected (Table 22-5) (9).

Design of DLTs

Plastic DLTs are molded (“memory” of the plastic) to conform to the shape of the airway. The tube is straight for most of its length (for the trachea) and then the distal endobronchial portion curves to the left. Since the distal end of the tube is inserted into the patient’s mouth under direct vision and the bronchial cuff is seldom torn; it is the fragile tracheal cuff that is damaged by the upper teeth if the glottis is anterior and laryngoscopy is attempted with an unbent tube directly from its package. The tube has to be bent into a “hockey stick” shape prior to laryngoscopy to avoid tearing the tracheal cuff. A Miller blade obstructs the view needed for DLT placement; a MacIntosh blade should always be used (10). Special adjuncts like the Bullard or Glidescope laryngoscopes and the Airtraq will help if a difficult airway is encountered.

After placement of a right-sided chest tube, the 16-year-old female trauma patient is brought to the operating room and ASA standard monitors are placed. A chest radiograph confirmed re-expansion of the right lung and a tracheal width of 15 mm was noted. Clinical examination reveals a Mallampati class I airway with normal neck anatomy, and cervical spine that has been cleared by radiologic and clinical exams. A rapid sequence induction is performed and direct laryngoscopy with a Mac 3 blade reveals a grade I view of the glottic opening.

Placement of DLTs

The DLT can be advanced into the trachea once laryngoscopy has established a view of the glottic opening. Initially, the tube should be held vertically at the “12 noon” position. Once the distal tip of the DLT is past the vocal cords the stylet in the bronchial lumen should be withdrawn. The tube should be rotated 90 to 180 degrees counter-clockwise until the distal tip is directed towards the left before advancing it further down the trachea.

With bulky rubber DLTs the conventional teaching was to advance the tube until moderate resistance to further advancement was encountered. With thinner plastic DLTs, especially if a small tube is selected, resistance as an end-point will result in the tube being inserted too deeply into the bronchus where it can obstruct the left-upper lobe bronchus (11). The depth of placement of left-DLTs for both men and women is highly correlated with patient height (12), and is easily expressed as DLT_cm = 12 + 0.1 (Height cm) (13).

Once in the bronchus, both the bronchial and tracheal cuffs should be inflated. If an appropriate (large) left-DLT has been selected, the bronchial cuff should require <3 mL air to seal the airway. If >3 mL of air is needed, the cuff is most likely in the trachea and the tube should be advanced further into the bronchus. The exception is the patient with a very large airway since a 41-Fr is the largest size DLT available and for some the left-bronchus may be large enough to accommodate a larger DLT. The volume of air needed in the bronchial cuff to seal the airway and the tension in its pilot balloon should be noted. If the DLT is subsequently displaced, the pilot balloon will soften. At this point both lungs should be ventilated.

The 16 year-old trauma patient now has a 35 Fr Mallinckrodt left-DLT inserted into her trachea and advanced to 27 cm. The tracheal and bronchial cuffs are inflated and the patient is ventilated through both the tracheal and bronchial lumens. The chest is auscultated and bilateral breath sounds are detected. However, when a FOB is advanced through the tracheal lumen, blood and secretions obscure the view. Despite multiple attempts, you are unable to confirm proper placement of the DLT using direct visualization with FOB.

Troubleshooting and Confirming Proper Position Using Clinical Signs Assess with Both Tracheal and Broncheal Lumens Open

A capnograph will demonstrate a wave-form and the appearance of end-tidal-CO₂. If both lumens are open to lung tissue water vapor should be visible in both lumens, bilateral chest wall excursion should occur, and bilateral breath sounds should be heard (Fig. 22-1A). If water vapor is seen in only one lumen (with both cuffs inflated) it is usually the bronchial lumen, and it often signals that the bronchial lumen has unintentionally entered the right-bronchus. It is also possible, although unlikely, that the tube is so deep into the left bronchus that the tracheal cuff is at the carina obstructing any ventilation of the right-bronchus.

Assess with Tracheal (Right) Lumen Closed

The next step is to clamp the tracheal (right) lumen while ventilating the left (bronchial) lumen (14). Breath sounds should be heard only over the (intubated) left lung (Fig. 22-1B). If breath sounds are present only over the right lung the DLT is in the right-bronchus (Fig. 22-1C). When this occurs, both cuffs should be deflated and the tube withdrawn several centimeters until its tip is above the carina. While bending and turning the patient’s head and neck to the right shoulder with the chin pointed to the left, the tube is re-rotated to the left and re-advanced (15). This maneuver usually redirects the tube into the left-bronchus. If the head-turn maneuver is unsuccessful after several attempts, a FOB should be inserted down the bronchial lumen, the left bronchus identified, and the FOB is used as a stylet to advance the DLT into the left-bronchus.

If while ventilating only the left lumen, breath sounds are heard bilaterally (with both cuffs inflated) the DLT is either not deep enough into the left bronchus (bronchial cuff not sealing the bronchus, Fig. 22-1D) or the tube is in correct position but the bronchial cuff has an inadequate amount of air to seal the bronchus.

Assess with Bronchial (Left) Lumen Closed

Once the DLT is in the left-bronchus, the left lumen should be clamped and the patient should be ventilated through the tracheal lumen. Breath sounds should now be heard only over the right lung (Fig. 22-1E).

If the DLT is still not in satisfactory position (with both cuffs inflated), ventilation through only the right (tracheal) lumen will be difficult or impossible because of very high resistance. The tracheal lumen’s orifice will be obstructed by the inflated tracheal cuff (above) and the inflated bronchial cuff (below). In this situation only the bronchial cuff should be deflated while ventilation through the tracheal lumen continues.

If the DLT is not deep enough bilateral breath sounds will immediately be present (Fig. 22-1F). If the tube is too deep breath sounds will be heard only over the left-lung (Fig. 22-1G).

Assessing Peak Inspiratory Pressures

While ventilating both lungs the peak inspiratory pressure should be noted. The bronchial lumen should be clamped and only the right lung ventilated, then the tracheal lumen should be clamped and the left lung is ventilated. If both lungs are relatively equal in volume, that is, in the absence of a pleural effusion, large mass or previous pulmonary resection, sequential ventilation of each lung should produce almost identical peak inspiratory pressures and end-tidal CO₂ waveforms.

If ventilation of the left lung (with a left-DLT) produces significantly higher peak pressures than with identical tidal volume ventilation to the right, the endobronchial lumen is probably partially obstructing the left-upper lobe bronchus and the tube should be withdrawn in 0.5 cm increments. If ventilation through the tracheal lumen (left-DLT) produces higher pressures than ventilation to the left, the bronchial cuff is probably herniating into the carina partially obstructing ventilation into the right bronchus. In this situation the tube is advanced in 0.5 cm increments until the peak pressures and waveforms become similar.

Reconfirm Position of DLT after Patient Repositioning

Once the patient is turned to the lateral position it is mandatory to reconfirm DLT position. A DLT is never advanced deeper into the airway but is frequently pulled out. The very first thing to do after turning the patient is to feel the tension in the bronchial cuff’s pilot balloon. If it is no longer as tense as when it was with the patient supine, the cuff is no longer completely in the bronchus. Do not add more air to the bronchial cuff, rather, both cuffs should be deflated and the tube should be advanced in 0.5 to 1.0 cm increments into the airway. The bronchial cuff should be re-inflated with the same volume of air that was initially used when the patient was supine; the pilot balloon should once again be tense.

Use of a FOB initially with the patient supine only serves to identify which bronchus has been intubated. Tube position changes with turning, so once the patient is in position for surgery a FOB should then be used to confirm DLT position. The FOB should be advanced down the tracheal lumen; the right-main bronchus should be open and a rim of blue from the bronchial cuff should be visible just below the carina in the appropriate (left) bronchus (16). If the bronchial cuff is fully visible, the tube can be advanced further into the bronchus. If the bronchial cuff is not visible the tube can be slowly withdrawn under direct FOB vision until a rim of blue is seen. Although seldom performed, the FOB should also be advanced down the bronchial lumen to demonstrate a patent upper-lobe bronchus.

Using clinical signs alone (Table 22-6), more than 98% of the left-DLTs functioned with appropriate lung collapse and satisfactory oxygenation during OLV (17).

References

1. Fitzmaurice BG, Brodsky JB. Airway rupture from double-lumen tubes. J Cardiothorac Vasc Anesth 1999;13:322–329.

2. Brodsky JB, Macario A, Cannon WB, et al. “Blind” placement of plastic double-lumen tubes. Anaesth Intens Care 1995;23:583–586.

3. Burton NA, Watson DC, Brodsky JB, et al. Advantages of a new polyvinyl chloride double-lumen tube in thoracic surgery. Ann Thorac Surg 1983;36:78–84.

4. Campos JH, Massa C. Is there a better right-sided tube for one-lung ventilation? A comparison of the right-sided double lumen tube with the single-lumen tube with right-sided enclosed bronchial blocker. Anesth Analg 1998;86:696–700.

5. Benumof JL, Partridge BL, Salvatierra C. Margin of safety in positioning modern double-lumen endotracheal tubes. Anesthesiology 1987;67:729–738.

6. Hannallah M, Benumof JL, Silverman PM, et al. Evaluation of an approach to choosing a left double-lumen tube size based on chest computed tomographic scan measurement of left mainstem bronchial diameter. J Cardiothor Vasc Anesth 1997;11:168–171.

7. Brodsky JB, Mackey S, Cannon WB. Selecting the correct size left double-lumen tube. J Cardiothorac Vasc Anesth 1997;11:924–925.

8. Brodsky JB, Malott K, Angst M, et al. The relationship between tracheal width and left bronchial width: implications for left-sided double-lumen tube selection. J Cardiothorac Vasc Anesth 2001;15:216–217.

9. Brodsky JB, Macario A, Mark JBD. Tracheal diameter predicts double-lumen tube size: a method for selecting left double-lumen tubes. Anesth Analg 1996;82:861–864.

10. Gaeta RR, Brodsky JB. A new laryngoscopy blade to facilitate double-lumen tube placement. J Cardiothorac Vasc Anesth 1991;5:418–419.

11. Brodsky JB, Shulman MS, Mark JBD. Malposition of left-sided double-lumen endobronchial tubes. Anesthesiology 1985;62:667–669.

12. Brodsky JB, Benumof JL, Ehrenwerth J. Depth of placement of left double-lumen endobronchial tubes. Anesth Analg 1991;73:570–572.

13. Takita K, Morimoto Y, Kemmotsu O. The height-based formula for prediction of left-sided double-lumen tracheal tube depth. J Cardiothorac Vasc Anesth 2003;17:412–413.

14. Brodsky JB, Mark JBD. A simple technique for accurate placement of double-lumen endobronchial tubes. Anesth Review 1983;10:26–30.

15. Neustein SM, Cohen E, Kirschner PA. Intraoperative left endobronchial tube positioning. J Cardiothorac Vasc Anesth 1991;5:101–102.

16. Slinger PD. Fiberoptic bronchoscopic positioning of double-lumen tubes. J Cardiothorac Anesth 1989;3:486–496.

17. Brodsky JB, Lemmens HJ. Left double-lumen tubes: clinical experience with 1,170 patients. J Cardiothorac Vasc Anesth 2003;17:289–298.

Laryngeal Mask Airway

Brian Egan, MD • Reuben L. Eng, MD

1) Overview

    a) The LMA is a supraglottic airway device that consists of a tube connected to an inflatable cuff; this cuff is inserted into the pharynx to permit ventilation of a patient under general anesthesia.

    b) It was invented by British anesthesiologist Archie Brain and introduced to clinical practice in Britain in 1983 and the United States in 1991.

    c) Today, the LMA remains one of the most commonly used supraglottic airway devices.

    d) Function of the LMA

  i) The LMA cuffed mask seals off the laryngeal inlet from the gastrointestinal inlet (Fig. 23-1).

  ii) The tip of the mask sits in the hypopharynx, at the level of the upper esophageal sphincter (UES), with the lateral aspects of the mask spreading into the pharynx, and the superior component displacing the base of the tongue forward.

  iii) The glottic opening and epiglottis sit within the “bowl” formed by this chamber; spontaneous ventilation (SV) or positive pressure ventilation (PPV) is effectively channeled via the bowl and into the respiratory tract (1).

2) Advantages of LMAs

    a) A supraglottic airway offers several advantages over an endotracheal tube (ETT) or mask ventilation, including

  i) Minimal hemodynamic changes with placement due to decreased stimulation with LMA placement

  ii) Low risk of dental/perioral trauma

  iii) First-pass success rates of up to 89%, and successful use in up to 98% of patients appropriately selected for LMA use (2)

  iv) Minimal airway reactivity upon placement, assuming appropriate anesthetic depth

  v) Low incidence of postoperative sore throat

  vi) Compared to a mask general anesthetic, the LMA frees the anesthesiologist’s hands from having to hold a mask

  vii) Minimizes coughing/pharyngeal irritation on emergence

  viii) Avoids tracheal intubation in special patient populations (e.g., singers)

1) Disadvantages of LMAs

    a) PPV is limited to peak airway pressures of 20 cm H₂O with the Classic LMA, and 30 cm H₂O with the ProSeal and Supreme LMAs.

  i) This limitation is due to the fact that the pressure at the lower esophageal sphincter (LES) is approximately 20 cm H₂O.

  ii) Ventilation with airway pressures >20 cm H₂O carries the risk of gastric insufflation.

    b) Although the aspiration risk is reported as <0.02% (3), the airway is not completely protected from aspiration of gastric contents.

  i) Patients at high risk of aspiration (e.g., obese, pregnant, gastroesophageal reflux disease, full stomach) may not be good candidates for LMA.

    c) Adequate function of the LMA is dependent on appropriate position in the hypopharynx.

  i) It is susceptible to displacement with changes in patient position and/or manipulation of the head and neck.

    d) Reported rare, but severe, neurovascular complications due to trauma secondary to LMA use include

  i) Lingual nerve injury (4)

  ii) Recurrent laryngeal nerve injury (5)

  iii) Hypoglossal nerve injury (6)

  iv) Tongue cyanosis (7)

Related posts:

Postoperative Nausea and Vomiting Chronic Obstructive Pulmonary Disease Malignant Hyperthermia Local Anesthetics Pulmonary Artery Catheter Adult Cardiac Surgery

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