Overview of Sellick Maneuver
Aspiration pneumonitis and pneumonia, or lung infections from breathing in foreign material, can be serious issues related to anesthesia during a medical procedure. In fact, they have been recognized as the most significant cause of death among all types of pneumonia. Reports indicate that as many as 15% of all legal claims related to anesthesia in the United States are due to aspiration, or breathing in foreign material. Also, in a study from the UK, aspiration was found to have the highest death rate out of all the reported issues related to the airway during anesthesia. The only airway issue reported more frequently was difficulty with intubation, which is the process of inserting a tube in the patient’s airway for them to breathe during anesthesia.
In 1961, a method was introduced by Sellick to reduce the risk of patients breathing in stomach contents while preparing for intubation. This technique, often referred to as the “Sellick Maneuver” or cricoid pressure, has since become a standard practice. It’s a unique feature of a process known as rapid sequence intubation, which involves quickly getting oxygen to the patient and inserting the breathing tube.
The cricoid pressure technique works mainly by applying pressure to the back part of the cricoid cartilage, a ring-like structure located beneath the cricothyroid cartilage at the C6 level of your neck. Sellick stated that this pressure technique blocks the esophagus (the tube connecting your throat to your stomach) at level C5. However, newer studies with advanced imaging technologies have suggested that the most likely target is what we call the post-cricoid hypopharynx, a region in your throat that includes part of the upper esophageal sphincter, a ring of muscle that helps keep the entry to your stomach closed when you’re not swallowing or vomiting.
Anatomy and Physiology of Sellick Maneuver
The cricoid cartilage is a rigid band that can be felt in the throat, positioned below the cricothyroid membrane which is a thin sheet in the neck. Imagining it as a signet ring, the band of the ring would be towards the front and the seal is at the back, which is the wider part and known as the lamina. This cartilage is aligned with the sixth bone in the neck spine (C6), similar to where the carotid tubercle, a small bump in the neck, is. It was found in one study involving patients extending their necks that this cartilage sat a bit higher, between the fifth and sixth neck spinal bones.
The inside of the cricoid cartilage can come in several shapes, including oval, rounded rectangle, or pear-shaped. Sellick, a researcher, originally thought that this cartilage was directly against the esophagus (food pipe) and that a backward push would block the esophagus to prevent any stomach contents from entering. He discovered that pressures within the stomach of up to 40 mmHg (a unit of pressure) could be stopped by applying pressure on the cricoid cartilage. However, this pressure doesn’t usually exceed 25 mmHg in most situations except in certain conditions like obesity, trauma, or other diseases.
However, experts now think the cricoid pressure targets the hypopharynx, the bottom part of the throat, as the esophagus starts below the cricoid ring. The cricopharyngeal muscle, a key part of this pressure system, is attached around the back and sides of the lower border of the cricoid ring. There are additional structures like the tendinous band and arytenoid muscles that keep the cricoid ring and hypopharynx connected. When cricoid pressure is applied, the musculature collapses turning kidney-shaped, which helps prevent regurgitation, or backward flow. The bulgy nature of the tissues around the windpipe and food pipe below the cricoid ring accounts for why the hypopharynx gets blocked off.
However, this technique appears to work even when the esophagus and the cricoid cartilage are not perfectly aligned and have moved aside. The hypopharynx remains the target. Other methods to seal off the esophagus, such as through the spaces beside the larynx (voice box) and trachea (windpipe), have been tried, but cricoid pressure is still found to be the more successful option.
Why do People Need Sellick Maneuver
Cricoid pressure is a technique used on patients at a higher risk of food or liquid entering their airways (also known as aspiration). It’s typically applied for people who may have eaten recently, are suffering from slow stomach emptying (gastroparesis), pregnancy, feelings of nausea, recent cases of vomiting, hiatal hernia, or a weakened esophageal sphincter (the muscle that stops stomach acid from flowing back up). This method is also used on those with increased belly pressure, those under the influence of alcohol, patients with neurological or upper respiratory reflexes issues.
Often, cricoid pressure is applied in emergency situations or during attempts to insert a tube into a patient’s airway (intubation). This procedure is particularly useful for patients with higher risk factors according to the American Society of Anesthesiology (ASA), as they have increased chances of aspiration events.
This technique has a significant impact particularly with pregnant patients as they are frequently at high risk for aspiration.
When a Person Should Avoid Sellick Maneuver
There are a few situations when the Sellick maneuver, a technique used during some medical procedures to prevent aspiration, is not recommended:
Firstly, though it doesn’t happen often, the Sellick maneuver can cause harm if a person is actively vomiting. This is because the technique might lead to a tear in the esophagus as the vomit tries to push past tightened throat muscles.
Secondly, if a person has a neck injury, it might not be advisable to use the Sellick maneuver. This is because the pressure applied to the back of the throat could potentially make the injury worse.
Lastly, it’s suggested that the Sellick maneuver should be stopped if it makes it hard for the doctor to see the larynx or voice box while inserting a device to help with breathing.
Equipment used for Sellick Maneuver
The original method for this procedure involved using an assistant’s hand. However, it’s been found that just using the fingers can be enough to apply the necessary technique and pressure. Along the same lines, there have been some new devices introduced to make the process more consistent and less open to interpretation.
For example, there is a device that provides a physical response, similar to a vibration, when you place your finger exactly as originally described. This has been found to apply the right amount of pressure consistently, and also to stop any excessive pressure being applied in the wrong direction.[12] Another example is a device that lights up to show when the proper pressure is being applied.[13] These inventions are considered to make the process more clear-cut and reliable than using your hand alone.
Who is needed to perform Sellick Maneuver?
Putting a tube into the windpipe requires the help of at least two healthcare professionals. This process is done with something called cricoid pressure – a technique used to prevent stomach contents from going into the lungs. The person applying the cricoid pressure should not let go until the tube is properly inserted and a special balloon-like part of the tube (called a cuff) is filled with air. Therefore, it’s virtually impossible for one person to do both things at the same time.
Preparing for Sellick Maneuver
It’s very important that all healthcare staff who might need to apply cricoid pressure, a technique used during some medical procedures, receive appropriate training. Research has shown that there can sometimes be a lack of consistent training in how to apply this pressure correctly and in understanding where exactly the cricoid is located in the body.
How is Sellick Maneuver performed
The cricoid pressure procedure typically needs at least two people. One person will insert a breathing tube into the patient’s airway, while the other person applies pressure to a specific part of the patient’s neck, known as the cricoid ring.
The patient is usually lying flat on their back with their neck stretched out. This position can change based on what is best to view the vocal cords, or glottis. Sometimes, the patient’s upper and lower neck may be adjusted separately to give the best view for the procedure. The aim is to direct any vomit or fluids away from the airway.
The person applying the cricoid pressure usually stands on the right side of the patient. They locate the cricoid ring by using specific features of the neck anatomy, like the thyroid cartilage (Adam’s apple area) and cricothyroid membrane (a thin sheet of tissue connecting the cricoid and thyroid cartilages). Once the cricoid ring is found, the person can apply pressure using either hand, making sure they don’t interfere with the person inserting the breathing tube.
The pressure is applied by placing the thumb on the patient’s right side of the cricoid ring, with the second finger on the opposite side. The third finger can be placed alongside the second finger if it’s more comfortable. The pressure is light while the patient is awake (about the same as a 1 kg weight), but it’s increased (about the same as a 3 kg weight) once the patient is unconscious. This pressure is sustained until the breathing tube is correctly positioned and inflated. For children, the pressure should be lessened due to the softer structures of their necks.
If there are concerns that the patient’s neck is not stable, a two-handed approach may be used. Here, one hand supports the back of the neck while the other applies the cricoid pressure.
It is usually recommended that a tube be placed into the stomach (gastric tube) before the breathing tube (intubation) in patients who have recently eaten. The placement of the gastric tube does not interfere with the effectiveness of the cricoid pressure. It’s important to not confuse cricoid pressure with the “BURP” technique, a different procedure used to improve visibility of the vocal cords during intubation.
Possible Complications of Sellick Maneuver
If a patient is awake or not fully under anesthesia during a certain medical procedure, they might feel uncomfortable, feel like throwing up, or be nauseous. Some serious issues that can happen include difficulty breathing, injury if they aren’t fully under anesthesia, tearing of the esophagus, breaking of the voice box ring, or making neck injuries worse.
Waiting until the anesthesia is fully in effect, using the right amount of pressure on the voice box ring, and providing proper support to the neck can help prevent some of these issues. Also, there are worries about artery being squeezed by some voice box ring tools, which are currently being examined.
One study showed that inserting a tube into the windpipe (intubation) might be a bit harder when applying pressure to the voice box ring versus not doing so. Surprisingly, there was no major difference in how often traumas occurred while inserting a tube into the windpipe between the two groups. There was also no difference in deaths, duration of hospital stays, or food entering the lungs. However, the chance of food entering the lungs was low at 0.5%, especially for pregnant patients, not including emergency cases.
What Else Should I Know About Sellick Maneuver?
The use of cricoid pressure, a technique used during certain medical procedures to prevent stomach contents from entering the lungs, is a bit of a mixed bag. The American Heart Association, for example, no longer recommends it in its guidelines for both in-hospital and out-of-hospital resuscitations. This decision was made due to difficulties in properly performing the technique in practice situations with medical mannequins.
However, some medical organizations, like the Obstetric Anesthetist’s Association and the Difficult Airway Society, do recommend using cricoid pressure. They suggest it’s used during a procedure called rapid sequence intubation, especially in patients who are at high risk, like those giving birth.
There is a lot of discussion about whether cricoid pressure is truly effective. Much of this debate seems to center on the inconsistent and incorrect ways it is applied. A study that tested the technique by applying it correctly and consistently in both high-risk and low-risk patients would be extremely valuable in settling this controversy.
In the United States, there seems to be more support for using cricoid pressure, likely due to concerns about legal issues. However, it’s important to remember that while cricoid pressure is based on expert agreement, there is minimal scientific evidence supporting its use. Ultimately, even with the use of cricoid pressure, it is not certain that it will completely prevent the aspiration, which is the entering of stomach contents into the lungs.