Second sight for anesthesiologists

Anesthesiologists have to get by and around a lot of things in order to put a breathing tube into a surgery patient. Kai Matthes thinks that using a pair of endoscopes could make the job easier. (National Cancer Institute)

Intubating the patient is a critical step in any surgery where general anesthesia is being used. But as any anesthesiologist will tell you, intubating a child is very different from an adult, largely because there is less space available in which to maneuver the breathing (aka endotracheal) tube.

There’s also less space in which to see. To place a breathing tube properly and keep the airway open, an anesthesiologist needs to see the patient’s vocal chords and the opening of his or her windpipe. Typically, the doctor uses a laryngoscope to see into the throat, but sometimes tumors, congenital anomalies, inflammation, or other obstructions block the view.

The next tool of choice would be a fiber optic endoscope – essentially a long, thin, tubular video camera – to peer within the throat. Sometimes, however, even the fiber optic scope can’t get a full view, and on occasion the scope and tube can get in each other’s way, making the anesthesiologist’s job harder and the procedure riskier.

But here’s a thought: If one scope can’t do the trick, what about two? Kai Matthes in Children’s Department of Anesthesia thinks that if he and other anesthesiologists could use two scopes at once, they could see everything they need to in a child’s throat, making the whole process of placing a breathing tube easier in patients where obstructions are anticipated or discovered.

“Ideally, we’d like to use a single scope that’s both flexible and stiff with a high resolution camera,” says Matthes. “And it should have a channel that we can use to suck out any saliva or other secretions blocking the view. But we’re limited in our choice of scopes by the size of the breathing tube, which in turn is limited by the size of the child.”

Knowing that no single scope fits all his criteria, he instead has developed a coupling system that joins two commercially available scopes of different sizes together, one next to the other:

  • A large diameter scope – he envisions using a gastric endoscope typically used for looking down the esophagus – would sit at the back of the throat, giving the anesthesiologist a view of the vocal chords and the top of the windpipe.
  • A smaller scope would serve the dual purpose of helping the anesthesiologist see past the vocal chords into the windpipe and act as a guide wire for the breathing tube as the anesthesiologist slides it into the airway.
An early prototype of a DEVRI dual endoscope system. Not only do the scopes give doctors a total view of the back of the throat, but the small scope also acts as a guide wire for the breathing tube.

Matthes thinks the dual endoscope approach – which he calls DERVI (for Dual Endoscope RendezVous Intubation) – could help circumvent many of the challenges to using fiber optic endoscopes for intubating children. “By using two scopes and displaying the video from both on a screen in a picture-in-picture layout, we can see both the vocal chords and windpipe continuously, as well as any obstructions, making the whole procedure safer,” he says. “Also, gastric endoscopes usually have large suction channels to help keep the view clear.”

He is currently working with Children’s chief of cardiac bioengineering, Pierre DuPont, to prototype the coupling system, thanks to a grant from the hospital’s Innovation Acceleration Program (IAP). “Once we can connect the two scopes and work out the mechanism for placing the breathing tube, we can try the DERVI technique in a simulation and, if it works, carry out a pilot study in patients,” he says.

Because it works with commercially available scopes, the costs of adopting the DERVI technique should be low, good news for doctors looking to use two eyes instead of one when keeping a child’s airway open.

[Ed. note: Matthes will give a presentation on the DERVI technique at the IAP’s Innovation Day, February 14, 2012, 1:00 – 5:00 pm. For more information, including registration information, visit the IAP website.]