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The Endotracheal Tube (ETT) and the Laryngeal Mask Airway (LMA) for General Anesthesia

Author:

I am a board-certified anesthesiologist in Lake Tahoe, California. I write from the perspective of both a doctor and a patient.

General anesthesia induces unconsciousness, which usually requires airway support.

General anesthesia induces unconsciousness, which usually requires airway support.

Airway Management during General Anesthesia

Providing oxygen during general anesthesia is the most essential requirement of anesthesia providers. General anesthesia means that unconsciousness is induced to block awareness and the senses. It is possible to breathe spontaneously and maintain your own airway during general anesthesia, but most people cannot do so adequately once unconscious with anesthesia.

The anesthesiolgist, therefore, must provide airway support and assistance. An endotracheal tube, placed into the windpipe, has been the most widely used device for this function. The laryngeal mask airway, described below, is a newer and less invasive method of securing the airway and delivering oxygen and gas anesthesia during a "general."

The decision of which to use is determined by many factors that have to be evaluated on a case-by-case basis.

What Do We Mean When We Use the Term "Airway"?

When we talk about your airway, we mean the passageway that air uses when you breathe on its way to your lungs.

  • mouth
  • nose
  • pharynx- palate, back of the tongue, uvula
  • larynx
  • neck
  • submental tissue

Endotracheal Tube in Sterile Packaging

The far end is placed into the windpipe through the vocal cords. The clear cuff is inflated by using a syringe on the blue pilot balloon. The other end of the tube protrudes from the mouth and has a connector that attaches to the ventilator.

The far end is placed into the windpipe through the vocal cords. The clear cuff is inflated by using a syringe on the blue pilot balloon. The other end of the tube protrudes from the mouth and has a connector that attaches to the ventilator.

how-does-anesthesia-affect-the-body

Endotracheal Intubation with an ET Tube

The standard method of securing the airway during general anesthesia has been intubation with an endotracheal tube. Once placed, the endotracheal tube (ET tube or ETT) reliably provides a pathway from an outside source of oxygen to the windpipe and lungs.

The Airway Assessment

The anesthesiologist begins to assess your airway in the preoperative evaluation. While he or she is talking to you, several points are noted about your mouth, head and neck. There are actually 11 points that are potential indicators of the ease or difficulty with which you can be intubated.

Placing the Endotracheal Tube

Breathing tubes are placed in unconscious patients (with special exceptions) to ensure and assist breathing. The end result of this essential function is delivery of oxygen to all the tissues of the body and elimination of carbon dioxide from the body. Once an ET tube is in place, a patient can breathe on their own, or have a ventilator (respirator) breathe for them.

During general anesthesia, a patient is rendered unconscious via IV medications in adults and anesthesia gases in small children after an adequate amount of oxygen has been given through a mask. Once "asleep," the breathing tube can be placed.

  • The head is gently extended back
  • The mouth is opened carefully
  • A special lighted scope, called a laryngoscope is inserted along the tongue to the back of the throat.
  • The lower jaw is lifted up and out to expose the vocal cords
  • The ET tube is placed between the vocal cords into the trachea (windpipe)
  • The ET tube's cuff is inflated
  • Position of the ET tube is checked by at least 2 different methods
  • The tube is secured with tape (usually) to the face

Complications and Side Effects of Intubation

  • Failed Intubation resulting in brain damage or death
  • Chipped or broken tooth (more common)
  • Sore throat (most common due to sensitivity of lining of throat)
  • Lacerations to lining of lips, mouth, pharynx or throat
  • Hoarse voice - temporary or permanent damage to vocal cords
  • Exacerbation of asthma in susceptible people
  • Increased blood pressure due to nervous system effects
  • Increased or decreased heart rate due to nervous system effects
  • Risk of spinal cord injury in patients at risk (broken neck, rheumatoid arthritis with neck involvement, severe deformity with cord compromise, etc).

Benefits of Endotracheal Intubation

  • Definitively secure airway
  • Easier to use and adjust ventilator and breathing parameters
  • Deeper levels of anesthesia possible
  • Better protection from aspiration and aspiration pneumonia

Intubation Complications: Potential Issues

Complications of intubation with an endotracheal tube range from the very minor to life-threatening. Luckily, the more serious the complications, the more unlikely it is to occur.

The biggest and most serious risk during intubation is failure to intubate. Anesthesiologists learn during their training to identify and prepare for the possibility that certain people will have what we call a "difficult airway." There are about 11 indicators that could point to a difficult airway. These range from characteristics of the mouth—like limited opening or high palate—to the obese neck with thick tissue that obstructs view of the internal structures.

The most serious consequence of inability to intubate is oxygen deprivation. Once the patient is asleep, there is a limited time frame to resume oxygen delivery. If unable to provide oxygen and ventilation, brain damage and possibly, death can result. This is a catastrophic event in anesthesia for everyone involved.

Other serious complications tend to also occur in specific patients for specific surgeries (e.g., increased internal pressure on the brain, dangerously high blood pressure, etc.).

Most adverse effects are not life-threatening. Sore throat is the most common side effect and can be expected to occur most of the time. Chipped or broken teeth are the most common complication (unexpected, but possible event). The laryngoscope has a metal tongue-depressor like blade that sometimes can contact the teeth. Pressure may be put on the upper front teeth if there is limited space inside the mouth or if the intubation is proving to be difficult. Often, teeth can be damaged if the patient bites down on the tube or bite block while waking up.

The Laryngeal Mask Airway

The soft rubber end is placed through the mouth, into the back of the throat. Air is added to the clear pilot balloon to inflate the mask for a secure fit. The hollow tube is connected to the oxygen supply and anesthesia machine.

The soft rubber end is placed through the mouth, into the back of the throat. Air is added to the clear pilot balloon to inflate the mask for a secure fit. The hollow tube is connected to the oxygen supply and anesthesia machine.

Close-up of the Underside of the LMA

This is a close-up photo showing the aperture for oxygen. The opening sits over the windpipe and allows oxygen to be delivered to the lungs.

This is a close-up photo showing the aperture for oxygen. The opening sits over the windpipe and allows oxygen to be delivered to the lungs.

The LMA is an Alternative to the Breathing Tube

The laryngeal mask airway (LMA) is an alternative to the ET tube that can sometimes be used. There are some factors that preclude use of the LMA (discussed below).

An LMA is a soft, inflatable plastic or rubber device that is essentially an oxygen mask that goes inside the mouth to deep in the throat. There is a hole in the device that sits over the opening to the windpipe. This opening is above the vocal cords and glottis (a natural flap over the windpipe), so we call it a supra-glottic device. It does NOT enter the windpipe like the endotracheal tube.

The opening on the mask leads to a wide tube that extends out of the mouth to be connected to the oxygen (and anesthesia gas) supply.

Because it does not go between the vocal cords, and because it is made of soft, flexible rubber, the LMA is less irritating to the airway than an endotracheal tube. Patients will still often report a sore throat after LMA use, but it tends to be less bothersome and of shorter duration than with a tube.

LMA Contraindications - When an LMA Can't Be Used

The LMA is a great alternative to the ET tube when it can be used. There are several reasons when the LMA cannot be used, however.

Certain patients and surgeries are not recommended or cannot be done with an LMA. These include:

  • Emergency surgeries where the patient has not fasted
  • Laparoscopic surgery
  • Chest surgery
  • Neuro and cardiac surgery where ventilation MUST be controlled
  • Lengthy surgery
  • Airway surgery
  • History of GERD/severe reflux
  • Obese patients
  • Patients with abnormal anatomy of the head, airway or neck
  • Patients with airway masses or obstructions

Potential Benefits of LMA

  • Less invasive/irritating, with less severe postoperative sore throat
  • No muscle relaxant/paralysis needed
  • Patient can breathe on his own
  • Less coughing and agitation on awakening from anesthesia

Breathing Tube (ETT) vs. LMA: How do We Choose

The LMA does have limitations to its use, as discussed. Because it is a supra-glottic (above the glottis) device, it does nothing to isolate the opening to the trachea (windpipe) from the opening to the esophagus (food pipe). This means that anything that could cause stomach contents to come up the esophagus put the patient at risk of getting those contents into the lungs.

Risk of aspiration is considered high or too high for certain patients and LMA use is not safe and an endotracheal tube must be utilized.

This category of contraindications includes people with moderate to severe reflux, those who have eaten within 6-8 hours, those who are obese, diabetics whose stomachs don't empty properly, pregnant women and others.

In addition, there are many surgical considerations that indicate an LMA can't be used for various reasons

  • lengthy surgeries (the LMA tends to lose function after a few hours)
  • surgeries in the prone position (if a patient is face-down and the LMA dislodges, it is difficult or impossible to replace it, causing a dangerous situation.
  • certain types of surgeries (e.g. laparoscopic surgery requires high pressure in the abdomen which makes ventilation with an LMA difficult)
  • surgery in which the breathing must be carefully controlled (brain, heart and chest/lung surgery)
  • surgery in the nose and mouth (any bleeding can drip into the back of the throat and potentially irritate the vocal cords or lungs)

Placement of LMA: This video helps visualize where the LMA sits in the back of the throat.

Potential Complications of LMA Insertion and Use

The biggest problem with LMA use is that sometimes it just doesn't fit or seal properly to adequately deliver oxygen. In this case, it can be removed and replaced with an endotracheal tube.

Because the esophagus and trachea are not separated (the openings are not isolated like they are with the endotracheal tube that blocks the trachea), there is a risk of aspiration in susceptible individuals. This can lead to problems with oxygen levels, damage to the lungs and a dangerous pneumonia.

Sore throats still occur with LMA, as mentioned.

Nerve damage has been reported with LMA use. This is a current area of study and more information should be forthcoming. It does not seem to be a common enough problem to advise against using an LMA.

Choosing an endotracheal tube or laryngeal mask airway

 ET TubeLMA

Spontaneous Ventilation

sometimes

usually

Controlled Ventilation

usually

sometimes

Prevents aspiration

mostly

minimally

Airway irritation

more

less

Choice for morbidly obese

yes

no

Good for lengthy surgery

yes

no

Choice for Surgery on Airway Structures (tonsils, nose, mouth)

yes

no

Choice for laparoscopy

yes

no

Choice for surgery in prone position

yes

no

Requires Visualization of Vocal Cords

yes

no

This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Comments

Michelle tolle on July 16, 2019:

In 2016 I had first a vagal nerve stimulator implanted for my epilepsy and then a month later I had a tonsillectomy with a sinuplasty done at the both surgeries I experienced a lot of problems with my talking my ENT doctor said I had paralysis on the left side of my vocal cords due to the intubation but that it would clear up is now 2019 it did not clear up as a matter of fact as the years go by it gets even worse sometimes I can't talk at all and sometimes I choke on everything I eat or drink will this ever get better is there anything they can do to fix it I was told that the wrong size intubation tube had been used and that's what tore my vocal cords in the first place both times in a row by the same anesthesiologist is there anything I can do about this and make things better

mandy on February 08, 2017:

My son is 10 years old with an infected tooth. He needs a baby tooth extracted under general anesthesia but I was told he would not be intubated. He does have acid reflux, post nasal drip, and he has seasonal nosebleeds that can last long. His lack of ability to open his mouth really wide makes me worry. I dont know whats safer intubation or no intubation for a baby tooth extraction

Mrs40sHistoryBuff on June 16, 2016:

Well, after briefly rereading my comments above, I noticed that, once again, "spell guess" has left its mark! I typed "upvote" and IT decided I surely must have meant "invite" instead! I thought I had caught all its devious word alterations before posting, but it would seem I got a little rushed at the end. Apologies for any confusion!

Mrs40sHistoryBuff on June 13, 2016:

I am a retired/disabled CST (Certified Surgical Technologist, and another lady behind the gown, cap, and mask in the O.R., for all the non-medical folks) and I read your Hub with great interest. Obviously I have had many opportunities to be in contact with anesthesiologists and associated staff members, but not just professionally. I did enjoy most of my contacts with members of your esteemed profession, but like all of us, there are always the odd exceptions!)

I have also had experiences on the other side of the OR bed, having been through about a dozen surgical procedures on my own body, including two right rotator cuff repairs, two knee surgeries, two spine surgeries for spinal stenosis and spondylolisthesis, facet disease erosion at four levels bilaterally, the last one including a fusion with hardware; an ablation for A-Fib of six years running and of unknown etiology, and several other procedures I'm not going to bore everyone else with, but I never had an untoward experience with my anesthesia. Not even when the results of the procedures didn't always go as well as could be.

Many times, I had the opportunity and privilege to select my own anesthesia provider, which I considered a significant benefit, as it just added to the number of caregivers in which I could have complete confidence!

I just got done reading your Hub, and found it to be completely understandable even on layman's level, which I have to sort of "gear down for" given my own level of education, and 15 years of experience in different facilities and services through time I spent (back in much better days) as a Traveler.

I think even if I had never been to the Community College Associates Degree program which prepared me for the work I dearly loved (and miss terribly) it would have been easy for me to understand it. Definitely an invite and a follow from me!

My best regards, as I am known professionally,

Shari Davenport, CST

kenny on May 12, 2016:

Thank u TahoeDoc. I learn a lot from you. Really appreciated. Keep going !!

Thanks

ARainey on November 02, 2015:

This hub was one of the most thorough hubs I've seen on hubpages. Strong work.

TahoeDoc (author) from Lake Tahoe, California on December 01, 2013:

Hi there. We often preferentially choose an LMA for people with reactive airways since the ETT seems to cause more irritation of the airways than the LMA. Also, sometimes we prefer the LMA for the reason that we can avoid giving muscle relaxants/paralytics and can give less anesthesia in general with an LMA. Fewer drugs may mean fewer drug related complications so that has to be balanced with any potential advantage of the ETT.

The decision of whether to use an LMA or ETT is dependent on many factors. Sometimes an LMA will have advantages over an ETT and sometimes it will be the other way around.

Unknown on November 27, 2013:

Hi , i have question here regarding lma and ett. Since ett has better advantages than lma in general , so any condition we prefer use lma than ett ?

TahoeDoc (author) from Lake Tahoe, California on September 18, 2012:

Lisa, that was so very thoughtful of you to come back to let me know. I'm glad everything went well! My child had surgery under general anesthesia when he was 19 months old, so I know it's one of those days that you dread, know is going to be unpleasant and you just have to get through. So, congrats! on getting through.

And, again, thanks for taking the time to give the update and the compliment!

Lisa on September 18, 2012:

Many Thanks again. The surgery was yesterday and went as well as could be. The anesthesiologist and the resident anesthesiologist who was there with her both came out to talk with me before the surgery, and I was even permitted into the OR to stay with my son until he started to go under general anesthetic. They handled things beautifully for us, allowing him to sit while we had the mask to his face, with a toy in his hand, and me right there, and then as he started to goto sleep, we gently lay him back. They used a small nasal tube, as he had dental surgery. The anesthesiologist explained that there was a 1/20,000 chance that he could have respiratory problems from the tube, and to see if his breath was raspy afterwards, and if he had trouble breathing later that night to come into emergency. But so far he has been pretty good. Just a little raspy but I'm sure part of healing now. He had no nosebleed afterwards, which we were glad about too. It was such a help to read your site and have your reassurances at times when we weren't able to ask our questions to anyone else. Thank you sincerely. Kind Regards, Lisa

TahoeDoc (author) from Lake Tahoe, California on July 28, 2012:

Hi Lisa. Actuallly, LMAs can be used for babies and small children. Not for dental surgery, however (if you are the same Lisa whose child is having dental extractions).

Intubating babies and toddlers is usually very routine and easy. If the palate is a problem, they will likely be able to tell this before putting the baby to sleep. Just mention it to the anesthesiologist before surgery (no guarantee that the nurse or dental surgeon will tell them).

A children's hospital is the perfect setting to ensure the safety of your child. Pediatric anesthesiologists are trained and experienced to care for, monitor, prevent or treat any events that come up. Most pediatric anesthetics are uneventful, however- that's how we like them too.

I know this is stressful for you, just get through it and look forward to it becoming a distant memory for both of you.

Lisa on July 28, 2012:

Hello,

I assume that a LMA would never be recommended for a 1 year old, even one who had never had spit-up? My son's only thrown up 3 times in his life, including spit-up, but from the risks of aspiration, it sounds like no chances would be taken with a baby. How common is failure to intubate though for a baby? And in the hands of an experienced anesthesiologist at a children's hospital, how concerned should I be about my 15 month old being at risk for low oxygen for any period of time? We know already that he has a very high palate. Thank you so much for taking the time and for your care!

TahoeDoc (author) from Lake Tahoe, California on May 24, 2012:

Thank you, mwilliams, for reading and commenting. There is a lot that goes into a "routine" anesthetic. The improvements in not only airway management, but pharmacy and monitoring have made general anesthesia much safer!

mwilliams66 from Left Coast, USA on May 23, 2012:

I have had 11 surgeries and the only question I had (regarding anesthesia) was whether to undergo a local or a general. You have provided valuable information that will certainly create additional questions for anesthesiologists. Your use of photos, tables and video has created a very easily understood hub. Voted up, useful and interesting.

TahoeDoc (author) from Lake Tahoe, California on May 22, 2012:

Thanks! I realize this won't mean much to a lot of people who haven't had surgery or faced these issues, but I get enough questions about this on my other hubs, that it seemed worth a separate article.

So, I appreciate you reading and commenting!

Amy Gillie from Indiana on May 22, 2012:

I like how you compared the methods in text and in an easy to read table. I've learned so much from reading this. Voted up!

Nettlemere from Burnley, Lancashire, UK on May 22, 2012:

Very thorough and authoritative hub and useful table at the end.