Overview of Difficult Airway
A “difficult airway” is a situation where healthcare professionals, even those skilled in managing airways, struggle with the usual methods of breathing aid. However, what precisely constitutes a “difficult airway” is not uniformly defined and can vary according to different professional guidelines.
The American Society of Anesthesiologists qualifies a difficult airway as a situation where a traditionally trained anesthesiologist has trouble with either using a facemask to aid a patient’s breathing, inserting a tube into the windpipe (tracheal intubation), or both. On the other hand, Canadian guidelines take a broader definition, including any situation where an experienced healthcare worker finds it tough to handle any of the common methods of airway management.
Several factors can contribute to a “difficult airway” like a patient’s unique characteristics, their medical and surgical history, the condition of their airway, the reason for needing airway management, and their current health state. Appropriate training, experience, thorough risk assessment, and good clinical judgment are crucial to predict the complexity of managing a patient’s airway confidently. In simple cases, the professional should manage the airway without any trouble, while complex cases might demand specialized techniques and equipment.
However, it’s essential to remember that predicting a “difficult airway” isn’t an exact science and can vary based on individual judgment. In reality, some studies suggest over 90% of “difficult airways” are unexpected.
To better manage such situations, organizations like the American Society of Anesthesiology and the Difficult Airway Society have outlined some algorithms or steps to follow. It’s vital that all healthcare professionals learn about the necessary equipment and techniques for successful intubation (inserting a tube into the windpipe). After all, failed intubation is a significant cause of sickness and death, according to the American Society of Anesthesiology.
Anatomy and Physiology of Difficult Airway
If someone is having trouble breathing, it’s important for the doctor to check their airway as soon as possible to see if there might be problems. The first check is to look for any issues with the person’s structure or physical features, that may be causing the difficulty. This check is crucial for those who have had any trauma to the face, head or neck, or who are bleeding in the mouth or have thrown up, or are foaming at the mouth.
If the patient can cooperate, doctors conduct an evaluation called a Mallampati test. During this test, the doctor will ask the patient to open their mouth to examine the size and condition of the tongue, how wide the person can open the mouth, and the condition and presence of their teeth and uvula, a small piece of flesh that hangs at the back of the mouth. The more of the uvula the doctor can see beyond the tongue, the easier it should be to perform a procedure called intubation, which is when a tube is placed into the windpipe to help with breathing.
The doctor will also examine the “thyromental distance” – the distance between the chin and chest when the head is in a neutral position. If this distance is small, it could make intubation harder. This is also true if the person has a severe overbite. If there has been damage to the neck, it might be difficult or unsafe to move the head into an optimal position for intubation.
In all situations where there is a risk of worsening neck injuries, the neck should be kept stable during every attempt to intubate. People who are overweight might also have a difficult airway. Excess skin folds in the cheek area and extra fatty tissue around the back of the throat can make it hard for the doctor to see the vocal cords, which is necessary for successful intubation.
Why do People Need Difficult Airway
Doctors may need to perform a procedure known as intubation for several reasons. This includes situations when your airway isn’t guarded safely, if there’s been an injury to your airway, if your level of consciousness decreases quickly or you lose consciousness altogether, and during certain procedures that require sedation and paralysis. The Glascow Coma Scale (GCS) is a medical tool doctors use to measure a person’s level of consciousness. If your GCS score is less than eight, it might also be an indication that you need to be intubated.
When a Person Should Avoid Difficult Airway
Just because a patient has a difficult airway doesn’t mean they should avoid necessary medical procedures. But, it’s important to know that if a person has facial injuries, it’s generally not advisable to use a medical procedure called direct laryngoscopy. This is a method where a doctor uses a special tool to look into your throat.
If a person is struggling to breathe, they must have a secured airway to ensure that they receive enough oxygen and can breathe properly. In such cases, it’s wise to have the most experienced health professional available oversee the handling of the person’s complex airway.
Equipment used for Difficult Airway
For a medical procedure called intubation, where a tube is put into your windpipe to help you breathe, the doctor will have some essential tools on hand. This includes a handle and blade from a laryngoscope (a tool used to see inside the throat), with a good light source, a tube that fits your windpipe size, a small inflatable cuff (a device to hold the tube in place), a stylet (a flexible rod used to guide the tube), and some oxygen.
A special device called an end-tidal carbon dioxide monitor is considered the “gold standard” – this means it’s the best way to make sure the tube is placed correctly because it checks for carbon dioxide, which is what we exhale. Suction equipment, if available, is also beneficial to have on hand to clear any obstruction.
When it’s time to put the tube in, certain medications are used. Propofol, for example, is used to determine whether or not you can receive oxygen through a small handheld device (a bag-valve-mask) before doctors administer medicine that relaxes and temporarily paralyzes your muscles (paralytic agents). Other similar agents can also be used for a process called rapid sequence intubation – but they won’t be used until it’s confirmed that you can get enough air through the handheld device.
If your airway is difficult to intubate, additional equipment will be close by. The type of tools available is based on the doctor doing the procedure and the equipment they have. Usually, a “difficult airway cart”, which contains a variety of useful tools, is present wherever intubations are frequently performed like the emergency department, the intensive care unit, or the operating room. This cart might have tools like a video laryngoscope, Combitube (a dual-tube airway device), bougies (long, thin plastic rods that help guide the tube down the throat), an intubating stylet, fiber-optic bronchoscope (a thin flexible tube with a light and camera), and an articulating laryngoscope.
Who is needed to perform Difficult Airway?
The medical team needed for this procedure includes the health professional who will be doing the intubation, which is a process of inserting a tube through the mouth and then into the airway. This is done so the patient can breathe properly. It’s not totally necessary, but having an assistant can be really useful.
When it’s thought that the procedure might be challenging, it’s really important that a specialist doctor called an anesthesiologist is involved early. An anesthesiologist is a doctor who is expert in providing anesthesia, which are drugs that reduce pain and sensation. They also make sure the patient is taken to an area where there are machines called mechanical ventilators. A ventilator is a machine designed to help or take over breathing for a patient who is unable to breathe effectively on their own.
Preparing for Difficult Airway
Before any medical procedure, it’s important that the patient is properly positioned on the bed. The patient’s body should be arranged in such a way that the back of their head is supported on the edge of the bed. Their head should be in a straight line with their spine and, if there are no issues with the neck, the head is slightly raised. This is often referred to as the ‘sniffing’ position. By adjusting the bed, the patient’s chest bone should be at the same level as the healthcare provider.
When possible, the lungs are cleared of nitrogen through a process known as ‘denitrogenation’. This is done by giving the patient 100% oxygen through a face mask for some time before the start of the procedure. After doing this, the patient should be able to safely stop breathing for 8-10 minutes, which is enough time for the medical team to place a tube into the windpipe to help the patient breathe. This process, called intubation, can take longer in some cases. It’s always best to make sure the patient has high oxygen levels before this process unless there are specific reasons not to. The same procedure is also performed in patients who are unconscious, but it’s important to check there are no blockages in the throat before providing the oxygen. The back of the throat can be checked and cleared if needed.
The healthcare team will ensure everything they need for the procedure is readily available beside the bed. This includes any medications, which would be prepared in syringes ahead of time. It’s also critical that the patient has a working IV line for administering medications directly into the bloodstream before starting with intubation.
How is Difficult Airway performed
If a patient has difficulty with inserting a breathing tube (intubation), it’s crucial to ensure there is adequate ventilation, especially if the patient is already sedated or unable to breathe on their own. This is achieved by using a mask attached to a small pump (self-inflating bag) with a source of oxygen. This mask covers the patient’s nose and mouth, while a healthcare expert uses his or her non-dominant hand to create a tight seal with the face and lift up the chin.
If the patient is overweight or it is challenging to create an optimal seal, two individuals might be needed for this ventilation process. If there is difficulty with the patient’s airway, it is crucial to get expert help quickly. In emergencies, an expert can provide ventilation using the pump and mask (bag-mask ventilation) while waiting for specialised equipment or other skilled healthcare providers to arrive.
There can be instances when inserting the breathing tube is not successful at first. This can lead to issues like increased pressure in the stomach, damage to the throat, and swelling in the neck. If no other options work, a surgical procedure might be needed to create an artificial airway.
Preferably, the healthcare provider should identify what equipment is available beforehand. This helps make informed decisions about how to proceed. A few tools used to manage such difficult airway situations can be a laryngeal mask airway, fiberoptic bronchoscope, intubating stylet, video laryngoscope and cricothyroidotomy kit.
In situations when the patient is breathing spontaneously, it is possible either to delay the administration of muscle relaxing drugs, or, if the patient has a history of difficult intubations, to intubate them while awake. In elective (non-emergency) intubations, numbing medicine (lidocaine) is used to numb the areas in the mouth and the throat, after which a fibre-optic bronchoscope (a long, thin, lighted tube) with a preloaded breathing tube (endotracheal tube) is introduced into the throat. The voice box is identified, and the scope passed through the vocal cords. After seeing the rings of the windpipe, an endotracheal tube is passed over the bronchoscope, and its position is confirmed. After this, the patient is sedated, and supplemental ventilation is provided. However, using a fibre-optic bronchoscope requires a lot of experience and may be difficult if the patient’s airway has blood or other secretions since the scope’s suction port is small.
In an emergency, the common practice is to clear the mouth (buccal cavity), attempt to ventilate the patient with a bag-mask, and then, if successful, move forward with inserting a breathing tube (intubation with direct laryngoscope). If the vocal cords can’t be seen due to an anterior larynx, a special type of laryngoscope blade can help with visualization. Also, there are scopes with lights that can help make seeing the cords easier. In challenging conditions, a laryngeal mask airway (LMA) can be inserted. However, it’s important to note that an LMA does not fully protect the airway and the patient could still inhale stomach contents. A surgical airway may also be required if all other measures fail.
If all efforts fail, and the patient still cannot be ventilated or intubated, a surgical airway might be necessary. If a healthcare provider foresees a potentially difficult airway, a surgeon should be notified early. Always remember that the correct placement of any airway device should be confirmed immediately using a device to measure the carbon dioxide levels.
Possible Complications of Difficult Airway
The process of inserting a breathing tube, known as intubation, can sometimes encounter issues. The most common issue happens when the tube accidentally goes into the food pipe (esophagus) instead of the windpipe (trachea). This problem can be hard to identify right away, especially in people who are overweight. Sometimes, the first signs are when the person’s oxygen levels start to drop even though they seem to be breathing okay. The best course of action in this situation is to remove the tube right away and switch back to using a face mask for oxygen. Also, it might be necessary to use a tube through the patient’s nose or mouth to relieve pressure in the stomach and lower the risk of inhaling food or vomit into the lungs.
Another problem could happen if the breathing tube goes too far into the lungs and enters one of the two main airways, usually the one on the right. This issue might raise the pressure in the lungs and can be confirmed by listening to the patient’s breathing, or looking at a chest x-ray. If this happens, the tube can be pulled back carefully until both lungs can be heard clearly when listening to the patient’s chest.
Occasionally, the vocal cords in the throat can get moved out of place during intubation, especially in tricky cases. This issue might not become clear until the tube is removed, which might cause the patient’s voice to sound hoarse, make breathing sounds (stridor), or even lead to breathing difficulties. If the tube getting stuck on a part of the throat (the arytenoids) causes this problem, the tube should never be forced in. If this happens, a throat, nose and ear doctor (otolaryngologist) should be brought in right away.
Also, there’s always a risk to the patient’s teeth during intubation. It’s important to use the laryngoscope (tool used to view the windpipe) properly to avoid chipping or breaking a tooth. If a tooth is broken, the pieces might be inhaled which would then require a bronchoscopy (procedure where a small tube with a camera is inserted into the lungs) to remove them. If a tooth is very loose, it might be best to have it taken out beforehand to avoid this problem. Bad teeth can harbor harmful bacteria, and inhaling these bacteria could lead to pneumonia or a blockage in the airways.
While rare, other complications from intubation such as intubating into the space between the lungs (mediastinum), causing a hole between the windpipe and food pipe (tracheoesophageal fistula), or narrowing of the windpipe (tracheal stenosis) can occur. If resistance is felt while the tube is being inserted, it should never be forced in. Instead, a smaller size breathing tube should be considered.
What Else Should I Know About Difficult Airway?
Having a blocked airway is a serious situation that can quickly become life-threatening if not appropriately recognized and managed. Health care professionals responsible for inserting tubes into patients to assist with breathing should be fully trained in three or four of these methods. If the first attempt at placing the tube (called intubation) is unsuccessful, a clear plan should be in place to correct whatever caused the failure in later attempts. The ability to help a patient breathe, supply them with oxygen, and keep their airway open is vitally important to their survival.
