If you’ve ever wondered why the little hole near the tip of an endotracheal tube is called the Murphy Eye, or who Macintosh was, or even who performed the first intubation, this quick trip through the history of endotracheal tubes and laryngoscopy is for you. Here are five things to know about the invention, indications and use of an endotracheal tube.
1. Endotracheal tube history
There is debate surrounding the details of the first endotracheal tubes. In 1543, Vesalius reported intubating an animal, the first documented case of a tracheal intubation [1].
Fast-forward to 1778 when Dr. Charles Kite is credited with developing the first endotracheal tube. In his “Essay on the Recovery of the Apparently Dead,” Kite describes a colleague’s tube saying “Mr. Savigny’s is, ‘an elastic tube, about 12 inches in length, to one end of which is fixed a piece of ivory, so constructed, that it may be blown through either by the mouth, or a pair of bellows adjusted to it; and to the other end, an addition of ivory also, of such a form as to enter and fill up a nostril [2].’”
It wasn’t until 1895 that we have a record of the first direct laryngoscopy. The procedure was designed by Alfred Kirstein who called his device an “autoscope.” It looked very much like the current Miller blades used by paramedics today.
Kirstein was motivated by a patient’s death caused when one of Kirstein’s colleagues misplaced an endoscope. This early version of the laryngoscope used sunlight to illuminate the vocal cords. Kirstein would stand behind his seated patient and, after placing the patient’s head in the “sniffing position,” he was able to directly visualize his patient’s larynx including vocal cords. This technique was soon used to place an endotracheal tube into the trachea [3, 4].
The laryngoscope continued to evolve. In 1921, Dr. Robert Macintosh developed his laryngoscope blade. The original blade is the number 3 blade still in use today [4].
Dr. Francis Murphy was a passionate believer in the idea that oxygen should be available when patients are undergoing anesthesia. In 1941, he proposed that an “ideal” endotracheal tube would be one that was both flexible and stiff enough to maintain its shape. It would also have features that keep it from easily being blocked.
The Murphy Eye was designed to allow continued ventilation in the event the distal end of the tube becomes occluded or otherwise obstructed by the carina, mucous or anything else that happened to get stuck in the distal end of the tube [5].
By the 1960s, endotracheal tubes were made of polyvinylchloride plastic. Inflatable cuffs were added to help keep stomach contents out of the lungs and allow for higher airway pressures [6].
2. Endotracheal intubation indications
Dr. Chris Nickson from the Life in the Fast Lane blog supports the use of an ABCDE mnemonic to help evaluate the decision to intubate. Most health care providers are familiar with the ABCs of patient assessment. This mnemonic builds on that and applies it to intubation decision making.
- Airway: Is the airway open and patent? Does the patient have a gag reflex?
- Breathing: Is the patient in respiratory failure?
- Circulation: Is the patient hypoxic?
- Disability: Is the patient unresponsive to pain?
- Exposure: What’s is the patient’s temperature?
- Other: Is airway management needed for safe transport?
There are various algorithms and checklists that help EMS providers decide whether or not to intubate. I think it’s important to note that if you are able to ventilate the patient, but they are not maintaining their airway on their own, non-invasive positive pressure ventilation is an acceptable option. Patients do not die from a failure to intubate; they die from a failure to oxygenate.
Still, inserting an endotracheal tube into the trachea remains a critical component in the standard of care in airway management. Successfully intubating the trachea usually keeps stomach contents from entering the lungs, causing damage and leading to infection.
3. Endotracheal intubation alternatives
Many experienced EMS providers will remember alternatives to an endotracheal tube that had names like esophageal obturator airway, pharyngeal tracheal lumen, Combitube and more recently the i-gel and King LT-D. Today, we have so many quality options for airway management that intubating a patient in cardiac arrest has been brought into question.
There is some evidence that the ideal crash airway isn’t an endotracheal tube, but one of the blind insertion or non-visualized airway devices. They’re easier and faster to use and they don’t require the clinical leader to become distracted from managing the patient while attempting to intubate.
4. Securing the endotracheal tube
These days, most EMS providers secure endotracheal tubes with a commercial device that uses a clamping mechanism of some sort to secure the tube and a strap to wrap around the back of the head/neck. These devices are widely available and are very effective and often include a bite block that is designed to keep the patient from biting down on the endotracheal tube.
If for some reason a commercial device isn’t an option, the endotracheal tube is typically secured using a cloth tape. There are several other options for securing endotracheal tubes that range from using a surgical mask to (my favorite) looping an NG tube through the nasal passageway and out through the oropharynx and buddy taping the ends to the endotracheal tube.
5. Endotracheal tube monitoring
Failing to confirm the proper placement of an endotracheal tube can lead to airway disaster. Anyone who intubates knows whether or not they saw the tube pass through the vocal cords. This observation, however, is NOT an objective method to confirm and monitor placement.
Continuous waveform capnography is considered the minimum standard for anyone intubating patients. There are plenty of examples where physicians and paramedics failed to recognize tube displacement and it resulted in death or serious injury to a patient. In situations where waveform capnography is inconclusive, the American College of Emergency Physicians suggests that ultrasound or radiography be used.
Intubation training
Many aspiring paramedic students see attaining the ability to intubate as a rite of passage. From the 1500s until today, techniques for placing a tube into the trachea have continuously evolved. Today, video laryngoscopy is pervasive and is in some places becoming the standard of care. In the next decade or so, we’re likely to have access to fully or partially robotic intubation, like this robotic device that uses infrared cameras to navigate itself into the trachea.
Read next: Improve endotracheal intubation with First and TEN approach
References
1. Ezri T1, E. S. (2005, December). PubMed.gov. Retrieved from National Center for Biotechnology Information: https://www.ncbi.nlm.nih.gov/pubmed/16400793
2. Charles Kite, J. C. (1778). An Essay on the Recovery of the Apparently Dead. Google Books. Retrieved from https://play.google.com/books/reader?id=WimT_r9aPDYC&printsec=frontcover&output=reader&hl=en&pg=GBS.PP3
3. Barash, C. S. (2009). Clinical Anesthesia 6th Edition. Philadelphia: Lippincott Williams & Wilkins. Retrieved from https://books.google.com/books?id=-YI9P2DLe9UC&lpg=PA7&ots=cj5eh9EcO1&dq=kirstein%20autoscope&pg=PA7#v=onepage&q&f=false
4. Burkle, Z. B. (2004). The Journal of the American Society of Anesthesiologists. Retrieved from Anesthesiology: http://anesthesiology.pubs.asahq.org/article.aspx?articleid=1943194
5. Wood Library-Museum. (n.d.). Murphy Endotracheal Tube. Retrieved from The Wood Library-Museum: https://www.woodlibrarymuseum.org/museum/item/530/murphy-endotracheal-tube
6. Frank Borschke, M. F. (2015, February ). The History of Endotracheal Intubation. Retrieved from Michigan College of Emergency Physicians: https://www.mcep.org/imis15/mcepdocs/Newsletters/Guest%20Editorial%20Jan-Feb%2015.pdf
This article was originally posted May 12, 2017. It has been updated.
