Endobronchial intubation to achieve one lung ventillation has absolute and relative indications.
Lung isolation to prevent spillage of pus or blood from an infected or bleeding source is an absolute indication for OLV. Massive atelectasis, sepsis, and pneumonia can result from contralateral contamination, which may be life-threatening. Bronchopleural or bronchocutaneous fistulae are low resistance pathways for the tidal volume delivered with PPV and alveolar ventilation will suffer without OLV. Additionally, large unilateral bullae or cysts are an indication for contralateral OLV as conventional two lung strategy can lead to rupture. With unilateral bronchopleural lavage, effective lung separation is required to avoid spillage of fluid from the lavaged lung to the nondependent, ventilated lung.1 Lastly, VATS procedures, for the most part, require OLV to facilitate exposure and are becoming the most common indication for lung isolation.
Relative indications for OLV generally involve cases where surgical exposure is considered high or low priority. For instance, pneumonectomy is commonly done using OLV. Upper lobectomy and thoracic aortic aneurysm repair are technically challenging procedures and often facilitated with lung isolation. Middle and lower lobectomy are considered less demanding of OLV. Esophageal procedures are also considered to be relative indications for isolation.
Methods of endobronchial intubation to perform lung isolation are manifold:
Double Lumen Tubes
Double-Lumen Endobronchial Tubes: The DLT is the most commonly used device to achieve lung separation today. Essentially two single-lumen tubes bonded together, one side is longer in order to reach a main-stem bronchus while the second, shorter lumen remains in the trachea. DLTs come in two varieties, right and left. The former has a slotted endobronchial cuff to facilitate ventilation of the right upper lobe while the latter does not have this adaptation. The Carlens tube had a carinal hook and was the first DLT available. It was used by pulmonologists for split function spirometry testing. The Robertshaw DLT was developed subsequently and it lacks a carinal hook. This tube design has advantages of having D-shaped, large-diameter lumens that allow passage of a suction catheter, offer low resistance to gas flow, and have fixed curvature to facilitate placement. The DLTs we use today are of the Robertshaw variety.
The most important advance in checking positioning of the DLT was the introduction of the pediatric flexible fiberoptic bronchoscope. It has been shown that when a DLT is thought to be positioned properly by auscultation alone, 48% of DLTs are malpositioned.
Numerous complications are possible when using DLTs. The most common one is malposition. If a left-sided DLT is advanced into the right mainstem bronchus, the RUL will not be ventilated and peristent hypoxemia can develop. Second, the DLT may be advanced down a mainstem bronchus so that the tracheal lumen lies below the carina. This will cause absent or diminished breath sounds over the contralateral side. The problem is corrected by pulling the tube back a few centimeters. Third, the bronchial lumen may not be advanced into a mainstem bronchus; inflation of the bronchial cuff will lead to inability of gas to flow from the tracheal lumen into the lungs. Fourth, if the bronchial lumen of a right sided Robertshaw DLT is not positioned to allow ventilation of the RUL, hypoxemia is probably inevitable. The mean distance from the carina to the RUL takeoff is 2.3 +/- 0.7 cm in men and 2.1 +/- 0.7 cm in women. Fifth, the LUL orifice may be obstructed by a left-sided DLT placed too far distally. The mean distance from the LUL orifice and the carina is 5.4 +/- 0.7 cm in men and 5.0 +/- 0.7 cm in women. Additionally, the bronchial cuff may herniate over the carina and occlude the contralateral mainstem bronchus with malposition or excessive cuff inflation. Finally, it is possible to cause tracheal or bronchial lacerations or even frank rupture with excessive force or use of improperly sized tubes. Excessive inflation of the bronchial cuff has also been associated with bronchial rupture. It rarely requires more than 2-3 mL of air to adequately seal a bronchus. The bronchial cuff should always be deflated prior to repositioning the patient.
Bronchial Blockers: A endobronchial blocker can be placed into the mainstem bronchus of choice using a bronchoscope. A cuff can then be inflated, effectively isolating that lung. A conventional single-lumen ETT can then be placed by routine means. This is usually the technique of choice for OLV in patients under age 12 since DLTs are not available for this patient population. Unfortunately, blockers can be fickle and can easily move out of position into the trachea, ruining lung separation
Advantages of Bronchial Blockers
Bronchial blockers can be advantageous in patients in whom intubation with a double lumen tube is difficult or impossible (easier to place, can ventilate while placing). They allow for isolation of particular segments of the lung. They are technically simple. They can be used in pediatric patients. They work with existing single lumen tubes and thus do not require tube exchange at the end of surgery
The Uniblocker is the most simple (essentiall a small bougie with a balloon at the end). The Arndt has a wire loop and the Cohen a wheel
Disadvantages include high cost and unreliable lung isolation
Advantages of Bronchial Blocker
- Technically simple
- Use in difficult / pediatric airways (small size, allow for ventilation during placement)
- Can isolate individual segments
- Work with SLTs (no tube exchange required)
(see also Miller Table 59-9)
Fogarty Catheter / Univent Tube
Arterial Embolectomy (Fogarty) Catheter and Univent Tube: A Fogarty catheter can be placed under direct vision using a bronchoscope into the mainstem bronchus of choice. A conventional ETT can then be placed alongside the catheter by traditional means. The Univent tube is a single lumen ETT with a moveable endobronchial blocker embedded in the wall of the tube. After intubation of the trachea, the blocker can be advanced into position with aid of a bronchoscope in the lumen of the ETT. The advantage of the Univent tube is that there is no need to change the tube at the end of a procedure, unlike a DLT (important if the patient has history of difficult intubation or if significant fluid shifts are anticipated). The biggest disadvantage of the Univent is that adequate positioning of the blocker portion can be difficult to maintain.
OLV in the Patient with a Tracheostomy: A separately inserted bronchial blocker, either within or alongside a single-lumen ETT that has been placed through the tracheostomy usually permits lung isolation. Sometimes passing a Fogarty catheter through the tracheostomy into a mainstem bronchus is easier because of the shorter distances involved, however.