Newsletter

June 2002 Newsletter:

CON:

Jerome M. Klafta, MD
Associate Professor, Clinical
Associate Chair for Education
Dept. of Anesthesia and Critical Care
University of Chicago

Bronchial Blockers Offer Certain Advantages for Lung Separation

Many practitioners consider placement of a double-lumen tube (DLT) the technique of choice for providing lung separation and/or one-lung ventilation in the practice of thoracic anesthesia and critical care. Modern bronchial blocker (BB) systems designed specifically for this use offer certain advantages over DLTs.

One of the challenges in using DLTs is selecting the appropriate size, a topic about which my co-author in this pro/con debate has published considerably. The appropriate size DLT may be defined as the largest tube that will fit in the mainstem bronchus with only a small air leak detectable when the cuff is inflated (1). A DLT that is too large will not fit in the mainstem bronchus or will do so traumatically, and a DLT that is too small may tend to migrate distally or fail to provide an airtight or watertight seal when its cuff is inflated with the appropriate volume of air (i.e., less than the cuff's resting volume, typically 2-3 cc for most DLTs) (2). Unfortunately, a patient's gender and height have fairly weak predictive value for selection of DLT size (3,4), and an uncomplicated, efficient, and thoroughly reliable method for choosing the right size remains to be found. Because lung separation with a BB is achieved when its balloon is inflated to the point at which it just seals the targeted bronchus, size selection of an independent BB is not an issue. Univent tubes do come in different sizes to accommodate the upper airway and trachea, but Univent size is less clinically important for most adult patients.

Another difficulty associated with the placement of a DLT is frequent tears of the tracheal cuff on a patient's teeth, even when direct laryngoscopy reveals an adequate view of the vocal cords. The incidence of this difficulty has not been recorded, but it is a problem with which almost every occasional as well as everyday thoracic anesthesiologist is familiar. This difficulty can delay or preclude successful placement and incur additional cost for wasted DLTs.

Just as DLTs have undergone design modifications, so have BBs. The Univent tube was introduced in 1982 and underwent modifications in 2001 (www.univenttube.com). The new Torque Control Blocker (TCB) Univent tube boasts a more flexible shaft which is easier to direct into the target bronchus and a softer, more compliant blocker. The manufacturer's claims have not yet been substantiated with data, however. The latest and perhaps most significant addition to the lung separation armamentarium is the Arndt wire-guided endobronchial blocker from Cook Critical Care (5). Introduced in 1999, this system minimizes many of the traditional difficulties associated with the use of Univent tubes and Fogarty catheters used as independent BBs. The patient's lungs can be ventilated while the blocker is fiberoptically positioned through a multiport airway adapter. The nylon guide loop at the blocker's tip couples it to the fiberoptic bronchoscope to facilitate precise placement. The wire-guided blocker has a small lumen in its shaft through which gas may be suctioned or oxygen insufflated.
DLTs offer the flexibility of switching ventilation from one lung to the other lung (for bilateral procedures) or to two-lung ventilation simply by clamping or unclamping lumens. Additional flexibility comes from the ability to suction blood or secretions easily from either lung. These advantages of a DLT cannot be disputed. However, independent BBs offer a different type of flexibility. They may be placed in a patient who is already intubated with a single-lumen tube (SLT) because of the need for mechanical ventilatory support, for example, or because of a difficult airway (5,6). Similarly, a patient who must remain intubated postoperatively need not be subjected to the risk of a tube change or the disadvantages of leaving the DLT in place. All that needs to be done at the end of the procedure is for the BB to be removed leaving the SLT in place. If a Univent tube was used for lung separation, its blocker can be fully retracted and the Univent can function as a SLT.

The flexibility to provide selective lobar blockade in a patient who cannot tolerate the exclusion of an entire lung's ventilation is another advantage of a BB. In a study of 30 patients undergoing pulmonary resections requiring one-lung ventilation, the Univent tube was used to selectively block the operative lobe or lobes (7). Selective lobar collapse plus 5 cm H20 of continuous positive airway pressure resulted in PaO2 values similar to those obtained during two-lung ventilation. The ease with which the BB can be positioned into lobar bronchi may be even greater with the Arndt endobronchial blocker since this BB is specifically designed to be fiberoptically guided.

Patients with tracheostomies who require lung separation may also be best managed with an independent bronchial blocker, particularly if the diameter of the tracheostomy stoma is too small to accommodate an otherwise appropriately sized DLT or Univent tube (8). Finally, the ability to rescue ill-fitting right-sided and left-sided DLTs with a BB has been described (9,10). These creative solutions to problems encountered with the use of DLTs highlight the fact that these two methods of lung separation are, in fact, complementary in certain clinical situations.

In summary, a DLT is a reasonable selection for most patients requiring lung separation. In some situations, however, there are clear advantages to the use of BBs. A convincing study demonstrating superiority of DLTs over newer BBs has yet to be performed. It is unreasonable to expect that anesthesiologists use BBs in situations in which the advantages are clear if they do not gain sufficient experience in using BBs in less critical situations. Just as using an LMA as a rescue device requires experience gained in routine cases, BBs should be used routinely to become a familiar part of the thoracic anesthesiologist's "toolbox."

References

  1. Hannallah MS, Benumof JL, Ruttimann UE. The relationship between left mainstem bronchial diameter and patient size. J Cardiothorac Vasc Anesth 1995; 9:119-21
  2. Hannallah MS, Benumof JL, Bachenheimer LC, Mundt DJ. The resting volume and compliance characteristics of the bronchial cuff of left polyvinyl chloride double-lumen endobronchial tubes. Anesth Analg 1993; 77:1222-6
  3. Brodsky JB, Macario A, Mark JBD. Tracheal diameter predicts double-lumen tube size: a method for selecting left double-lumen tubes. Anesth Analg 1996; 82:861-4
  4. Slinger P. Choosing the appropriate double-lumen tube: a glimmer of science comes to a dark art. (editorial) J Cardiothorac Vasc Anesth 1995; 9:117-18
  5. Arndt GA, Buchika S, Kranner PW, et al. Wire-guided endobronchial blockade in a patient with a limited mouth opening. Can J Anaesth 1999; 46:87-9
  6. Klafta JM, Ovassapian A. Lung separation and the difficult airway. Probl Anesth. 2001; 13(1): 69-77
  7. Campos JH. Effects on oxygenation during selective lobar versus total lung collapse with or without continuous positive airway pressure. Anesth Analg 1997; 85:583-6
  8. Tobias JD. Variations on one-lung ventilation. J Clin Anesth 2001; 13:35-9
  9. Nino M, Body, SC, Hartigan PM. The use of a bronchial blocker to rescue an ill-fitting double-lumen endotracheal tube. Anesth Analg 2000;91:1370-1
  10. Capedeville M, Hall D, Koch CG. Practical use of a bronchial blocker in combination with a double-lumen endotracheal tube. Anesth Analg 1998;87:1239-41

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