EMS-Delivered Airways, Part II

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Many EMS providers use devices like the King Laryngeal Tube or Sheridan Combitube as primary or rescue airways (if tracheal intubation fails). The pharyngeal balloons on the King LT or Combitube make them very secure to dislodgement. They are also blindly inserted and require relatively little training.

Mastering the ins and outs of the Combitube and the King LT airway devices

Many EMS providers use devices like the King Laryngeal Tube (LT) or Sheridan Combitube as primary or rescue airways (if tracheal intubation fails). The pharyngeal balloons on the King LT or Combitube make them very secure to dislodgement, unlike other airway devices like tracheal tubes or LMAs. They are also blindly inserted and require relatively little training.

In the UK and parts of Europe, the LMA has become a commonly used pre-hospital airway, but this is generally not the case in the US.  The LMA Supreme incorporates a fixed curvature for simple insertion, along with a gastric decompression port, making it an ideal LMA for field use. Some EMS agencies in the States are using it as a rescue device, though I am not aware of any using it primarily.

The King LT has largely replaced the Combitube in many EMS systems and the US military for many reasons: a simpler design, single inflation port (and syringe), smaller overall size, easier insertion, and lower potential for unrecognized esophageal ventilation.

The King LT comes in two models; the LTS-D and the LT-D.  The LTS has a gastric channel, while the LT-D doesn’t.

Combitube – 2 lumens, 2 balloons (combitube.org):
1) Twin-lumen device with two balloons: Balloon #1 (beige) seals pharynx, balloon #2 (white) seals esophagus. 2) Lumen #1 (blue  proximal connector) goes to ventilation holes between balloons, while lumen #2 (clear proximal connector) runs completely through to dital tip. 3) Excellent seal pressures, trachea fully isolated from esophagus.

The ventilation holes on a King LT and Combitube are positioned over the laryngeal inlet in a location similar to where a LMA mask sits.  The King and Combitube devices seal the proximal esophagus and the base of the tongue with two balloons. With an LMA the mask tip wedges into the upper esophagus and the remainder of the mask seals the laryngeal inlet. None of these devices can be used in a patient with an intact gag response and none do well with vomitus filling the airway, as they all will channel the vomitus directly into the larynx.  Accordingly, it is very important that providers be careful about ventilation volumes and pressures.  Recommended ventilation volumes in emergency airways are 6-7 cc/kg, delivered over 1-2 seconds, using pressures less than 20 mm Hg.  If the patient regurgitates around the distal tip of any of the devices, aspiration is almost guaranteed.  If the vomitus is thick or contains large food chunks, it may occlude the ventilation holes entirely, rendering them completely ineffective.  If during a resuscitation the patient’s mental status improves, it is important to recognize this early and administer a muscle relaxant to prevent vomiting (assuming the airway is left in place). 

Esophageal (above) vs tracheal placement (below) of Combitube showing proper ventilation lumen:
1) Combitube enters esophagus in >95% of cases (top): ventillation through lumen #1 (blue connector) via supraglottic holes between balloons. 2) Combitube in trachea (bottom): ventillation through lumen #2 (clear connector) via open lumen at distal tip in trachea.

Both the King LT and Combitube are intended to have their distal tip placed in the esophagus.  With the King LT the pharyngeal balloon and esophagus balloon are inflated through a single inflation port and pilot balloon, while the Combitube has two ports and pilot balloons. There has been one case report where over-inflation of the esophageal balloon collapsed the trachea (from behind), preventing ventilation even though the tip of the device was in the esophagus.  The protocol for ventilation with the Combitube is to try to ventilate with lumen 1 (blue lumen), try lumen 2 (transparent) lumen, in case the tip went into trachea directly, and if these both fail, advance the device slightly, because the pharyngeal balloon might be down-folding the epiglottis.  With the King LT, the device is inserted as deep as possible (after picking the correct size), the balloons inflated, and then the device is gently withdrawn until ventilation is achieved.  Tracheal insertion with the King LT can occur, though it is much less likely than with the Combitube, since the device is much shorter and more flexible. If this happens, ventilation will not be possible until the device is withdrawn.

The King LTS-D is a single use suprablottic airway that uses two cuffs to create a supraglottic ventilation seal but has only one ventilation port and a single valve and pilot balloon. Recommended sizes: #3, 4-5ft; #4, 4-5 ft; #5, >6 ft.
1) Place device around tongue (either midline or lateral approach) until gastric access lumen is at teeth or gum line. 2) Inflate according to size of device (range 45-90 ml) and test for optimal ventilation while withdrawing device adn gently bagging. After easy ventilation is achieved, check cuff pressure and adjust to approximately 60 cm H2O.

Transitioning from a King LT or Combitube to intubation usually means removing the device.  There is no method for intubating through a Combitube.  The recommendation from the manufacturer is to take the pharyngeal balloon all the way down (deflate it), leave the esophageal balloon in place as a seal, and intubate around the device.  This is often impossible to do because of space restrictions and problems inserting a tracheal tube around the bulky Combitube.  With the King LT there is a lumen that runs through the main ventilation lumen and comes out between the two balloons, assuming the holes are optimally positioned over the larynx.  It is possible with a thin fiberscope to pass through this lumen into the trachea, and either place a wire or Aintree catheter, and then intubate over one of these devices.  In practice, the lumen through the King is really small, very tight for either a bougie or fiberscope, and it’s really tricky to enter the larynx, pass another object into the trachea, and then railroad a tracheal tube over this second device.  Unless an ED physician is very familiar with the King LT, flexible fiberoptics and the Aintree catheter and the patient is completely stable with the King LT, I would not recommend trying this.  

In a cardiac arrest situation, I would focus on resumption of cardiac activity before switching out the prehospital airway, assuming the airway is functional (good breath sounds, end-tidal CO2, etc.).  If there is vomitus in either the King LT or Combitube when EMS delivers the patient, suction the gastric port quickly, remove all the air out of balloons (there are two pilot balloons on the Combitube, a shared pilot balloon on the King), and pull the device.  Before tossing it in the trash, make s
ure intubation with a tracheal tube can be accomplished.

It is helpful to know how long the airway was in place prior to arrival.  Lingual edema due to prolonged placement and over-inflation of the pharyngeal balloons has been described with both the King LT and Combitube.  Some trauma institutions with long EMS transport times have chosen to switch out these devices in an OR setting instead of the ED.  While this is not considered standard of care, I would inspect the tongue to see if it is enlarged, purple and rock hard; if so, a difficult airway after removal should be expected. 

Dr. Levitan teaches emergency medicine at Jefferson Medical College and at the Univ. of Maryland and helps run a monthly airway management course involving specially prepared cadavers: jeffline.jefferson.edu/jeffcme/Airway

Images reproduced from Levitan RM, Airway Cam Pocket Guide to Intubation, 2nd Ed., Airway Cam Tech.Inc., Wayne PA, 2007; Used with permission.

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