Overview of Direct Laryngoscopy
A direct laryngoscopy is a tool that helps doctors clearly see the voice box, or larynx. They usually use this tool during general anesthesia, surgeries on the voice box, or when helping a patient to breathe. This tool is highly useful in many hospital areas like the emergency department, the intensive care unit, or the operating room.
By helping the doctor to see the voice box, a direct laryngoscopy makes it easier to insert an endotracheal tube. This is a tube that goes into the windpipe to help with breathing. It is crucially important for patients who aren’t able to manage their own breathing, such as those who aren’t fully aware or those going through surgery.
When using a direct laryngoscopy to aid a patient’s breathing, the doctor needs to have good knowledge about the body part, why and when it should or should not be used, how to prepare, what equipment to use, the correct practice, personnel, and potential complications of the procedure to successfully carry out endotracheal intubation – that’s the process of inserting the breathing tube.
Anatomy and Physiology of Direct Laryngoscopy
The larynx, often referred to as your voice box, sits just below a part of your body known as the pharynx. It’s made up of several parts including six small cartilages and various muscles. The three pairs of cartilages are named arytenoids, corniculate, and cuneiform. There are also three larger, stand-alone cartilages, known as the cricoid, thyroid, and epiglottis.
The cricoid cartilage is special because it’s the only one that wraps around your windpipe, known medically as the trachea. The epiglottis sits above the cricoid cartilage. It’s an important part for doctors to find when they perform a procedure called a direct laryngoscopy. The epiglottis is located at the base of your tongue and offers protection to your voice box by acting like a lid over the opening (glottis) to prevent food or drink from entering your windpipe when you swallow.
Just in front of the epiglottis and at the base of the tongue, there’s a little pocket of cartilage called the vallecula. This is another significant landmark for doctors during a procedure like a direct laryngoscopy. When a curved special tool known as a Macintosh blade is used in the procedure, it’s inserted into this pocket to help the doctor see the vocal cords better. Once the blade is in the vallecula, it pushes against a tissue called the hyoepiglottic ligament. This ligament connects the epiglottis to a bone in your neck called the hyoid, essentially hanging the epiglottis from this bone.
Why do People Need Direct Laryngoscopy
Direct laryngoscopy is a medical procedure used to view the throat and voice box area, and is commonly used to place a breathing tube (endotracheal intubation) in emergency or critical care situations. In simple terms, this procedure might be needed in the emergency room if a patient is struggling to breathe, might have their airway blocked, or needs help preventing food or liquid from entering their lungs – for instance, if their mental state is altered, if they’re throwing up blood due to issues with their stomach or esophagus, or they can’t breath because of high levels of carbon dioxide in their blood (hypoxia or hypercapnia).
Furthermore, in a surgical setting, this procedure might be necessary for people who are under general anesthesia (medicine to help them sleep during surgery), during surgeries near the throat or airway, or surgeries where the patient needs to be positioned on their stomach, such as spinal surgery.
In this intensive care unit (a special department of a hospital that provides intensive treatment), this procedure might be needed for patients threatened with airway blockage, for providing brief, forced ventilation to patients with high pressure inside their skull due to bleeding, tumors or lumps in the brain. It may also be done to manage large amounts of mucus or other fluids that a patient can’t clear on their own. All of this helps keep the patient’s airway open and clear for breathing.
When a Person Should Avoid Direct Laryngoscopy
Performing a direct laryngoscopy, a procedure used to examine the voice box and throat, is not always safe or possible for every patient. In some severe situations, it might be unthinkable like situations involving sores or tumors affecting the throat or voice box which can prevent the successful use of the breathing tube in the right way. Also, if someone has suffered serious throat injuries due to a blunt force impact resulting in a broken voice box or damage to the windpipe, this procedure can lead to further harm. In these scenarios, a surgical intervention to create an artificial airway is the only solution
Direct laryngoscopy is not permitted if there is a deep wound in the upper airway. The movement caused by the procedure could cause a blood-filled swelling, or potentially cut the airway. In such cases, it’s vital to achieve ventilation and transfer of oxygen by non-invasive ways until a confirmed surgical airway is created.
A condition called trismus (when someone can’t open their mouth fully) with less than 1 cm opening between the upper and lower teeth front teeth is also a crucial reason to dismiss direct laryngoscopy. In practical circumstances, even grade II trismus often makes this procedure unachievable.
Throat conditions caused by infections, burns, or severe allergic reactions that result in extreme swelling of the voice box can also hinder direct laryngoscopy. This is because the swollen tissues could make the entrance of the airway hard to visualize. Furthermore, any irritation from the laryngoscope or the breathing tube will only make the swelling worse, which can then limit the chances of successful oxygen support with a mask and ventilation. In these cases, the procedure may only be performed if there are immediate plans for a surgical airway in the event that the procedure proves unsuccessful.
There are some other conditions where the direct laryngoscopy may not be the first choice due to certain complications. These include patients having a difficult airway to access, e.g., a small lower jaw or an overly large tongue, or having a high risk of difficult endotracheal intubation according to the Mallampatti score (a measure of mouth and tongue size). Patients with neck, throat, or larynx trauma also fall into this category. Furthermore, for patients suffering from airborne diseases like Tuberculosis, COVID19, or Ebola, this procedure should be avoided as it can aid the transmission of the virus to healthcare personnel. Instead, video laryngoscopy performed with particular protocols to minimize airborne particles is recommended for these patients.
Equipment used for Direct Laryngoscopy
Before beginning an examination of the throat using a laryngoscope (a procedure called direct laryngoscopy), it’s crucial to set up a few things first. The patient needs to be connected to heart rate monitoring equipment and a machine that continuously measures the level of oxygen in their blood (a pulse oximeter). A suction device must be prepared and within reach for immediate use. Good lighting and the correct positioning of the patient are also vital for the success of the procedure. Using the right equipment and preparing the patient properly are both key to this procedure.
The main tools used for a direct laryngoscopy and later for inserting a breathing tube into the patient’s trachea (endo-tracheal intubation) include a laryngoscope handle, special blades for the laryngoscope (Macintosh or curved, Miller, or straight blade with a curved end, or Jackson-Wisconsin or straight), and breathing tubes of appropriate size, usually one size bigger and smaller for safety. A cuffed tube of 7.5 mm is used most commonly in emergencies or surgeries. In an intensive care unit, the health team usually prefers larger tubes. They facilitate suctioning mucus from the trachea and also enable a flexible bronchoscopy (a procedure to look inside the airways) through the tube. These larger tubes also offer less resistance when the patient is connected to a ventilator, but they shouldn’t be so big that they could risk injury to the voice box or cause narrowing of the upper windpipe.
In addition to the laryngoscope, blade, and breathing tube, other necessary supplies include a sterile lubricant for the cuff and balloon on the breathing tube, and a syringe (at least 10 cc) to inflate this balloon once the breathing tube has been successfully placed.
Additional equipment for direct laryngoscopy includes accessory airway management devices such as an endotracheal tube introducer (often called a “Bougie”), oral and nasal airways, and backup airway devices like a Combitube or supraglottic airway tubes. A device that measures exhaled carbon dioxide (capnography) is needed to confirm the correct placement of the breathing tube. Backup devices to access the airway, such as video laryngoscopes, rescue airway devices (like a laryngeal mask airway), and emergency airway kits for creating an opening in the neck (cricothyrotomy) or in the trachea (tracheostomy) are included in the equipment set. If a difficult airway is expected, the health team should be ready with the surgical airway tools even before starting laryngoscopy.
Who is needed to perform Direct Laryngoscopy?
The task of inspecting the voice-box using a tool called laryngoscope involves professionals from various hospital departments. For instance, doctors in the emergency room use this technique for placing a tube into patients’ windpipes in critical situations. Anesthesiologists, who are doctors specialized in ensuring pain-free surgeries, also frequently use this method during surgery to ensure the patient can breathe properly. Doctors who specialize in critical care use this method if there’s a need to secure a patient’s breathing passage.
There are also specific kinds of doctors, like otolaryngologists or general surgeons, who might step in if there is a high risk of needing a surgical procedure on the airway. An otolaryngologist is a doctor that treats ear, nose, and throat conditions.
Preparing for Direct Laryngoscopy
Before a medical procedure that involves the use of a tube to help breathing (referred to as endotracheal intubation), the doctor needs to assess the patient to determine how easy the procedure will be. Some features can make it hard for the doctor to see the larynx (the part of the throat involving your voice box) making the procedure trickier. These include:
– The gap between the top and bottom incisor teeth measuring less than 1.6 inches.
– The distance from the thyroid cartilage to the chin (thyromental distance) measuring less than 2.4 inches.
– A distance from the sternum (chest bone) to chin (sternomental distance) of less than 4.7 inches.
– The patient’s head and neck can only extend less than 30 degrees from a normal position.
– Mallampati class 3 or 4, a system that scores the visibility of the throat structures, which can indicate difficulty in a breathing tube insertion.
– A smaller than average mandible (retrusion), the bone that forms the lower jaw.
– Neck circumference of more than 15.7 inches.
– Reduced flexibility of the area under the chin (submental compliance).
– A history of cervical spinal fusion, an operation to join selected bones in the neck.
– Scarring from radiation or burns in the neck.
After assessing the patient, it’s critical to ensure the patient receives enough oxygen. If the patient is expected to have a difficult intubation or might lose oxygen rapidly, the doctor can use a method called apneic oxygenation. This process involves providing oxygen through a nasal tube at a certain rate.
To be prepared for any situation, a suction device and a bag-valve mask (a device used to assist in breathing) should be ready, alongside devices to monitor blood pressure, oxygen levels in the blood, heart activity, and the amount of carbon dioxide after exhaling.
In addition, the doctor ensures an intravenous line is established for giving any required drugs. Lastly, all the necessary medications and emergency equipment need to be prepared and ready at hand, including but not limited to agents that put the patient to sleep (induction agents), agents that cause muscle relaxation (neuromuscular blocking agents), and any additional necessary medications.
How is Direct Laryngoscopy performed
Direct laryngoscopy, a procedure used to look at your throat and voice box, involves several specific steps.
First, you’ll be positioned properly. The usual position is called the “sniffing” position, where your neck is extended and your head is raised about an inch to three inches. But if you have a neck injury, your head and neck won’t be moved around.
After you are positioned, your doctor will open your mouth using their right hand. They often do this with a technique called the “scissor technique.” To do this, they use their thumb and middle finger in a scissor-like motion, with the thumb pressing onto your lower teeth and the middle finger pressing onto your upper teeth.
Your doctor will then insert a tool called a laryngoscope into the right side of your mouth. This tool has a light and a small camera for the doctor to see inside your throat. They use this tool to move your tongue to the left. Depending on what your doctor needs to see, they use the laryngoscope blade either at the back of your tongue (if they’re using a tool model called the Macintosh) or by your epiglottis, which is the flap of tissue at the base of your tongue (if they’re using a tool model called the Miller).
The doctor would then slightly move your laryngoscope towards the front to see the vocal cords better.
If your voice box’s entrance (your airway) is more towards the front, an assistant might use gentle pressure on an area in your neck called the cricoid while the doctor lifts the laryngoscope to get a better look at your airway.
Possible Complications of Direct Laryngoscopy
Like any other medical procedure, issues may arise when using a laryngoscope – a device used to view the throat and voice box. This device might accidentally hurt the throat, voice box, windpipe, teeth, or lips.
Using a laryngoscope also comes with the risk of harming the vocal cords or displacing the cartilage in the throat. Therefore, doctors need to be very careful during the procedure to avoid these complications.
The most common problem after this procedure is a sore throat. This can happen in about 14% to 57% of people who have a tube placed in their throat for general anesthesia. A sore throat can include pain, discomfort, a hoarse voice, difficulty swallowing, and dry throat. However, this discomfort is normally mild and short-lived, often disappearing within 48 hours.
Issues related to the use of a laryngoscope and placing of the tube (endotracheal tube, ETT) can be grouped into two types: traumatic (physical injury) and non-traumatic. Physical injuries might include damage to the throat, voice box, or windpipe from the laryngoscope or the tube. Also, damage can occur to the lips, tongue, pharynx (back of the throat), esophagus (food pipe), and teeth. Chipped or broken teeth due to improper technique are a significant issue. In rare cases, moving the neck too much during the procedure can injure the neck’s spinal cord.
Non-physical complications of this procedure might include food or liquid from the stomach going into the airway, lack of oxygen to the brain, and sudden tightening of the airways. The procedure can also lead to a sudden increase in heart rate, irregular heartbeat, and changes in blood pressure. In young patients, the laryngoscope might slow down the heart rate. Placing the tube in the food pipe instead of the windpipe might happen but is usually noticed and corrected quickly. Other known complications include injury to the lungs and low blood pressure.
Long-term issues might also occur due to irritation to the tissue from the tube, causing scarring. This can lead to deformities in the windpipe or the voice box.
What Else Should I Know About Direct Laryngoscopy?
Direct laryngoscopy is a useful procedure that medical professionals often use in different areas within the hospital. It’s a standard technique for safely inserting a tube into the windpipe (intubation) and performing throat surgery. The procedure is used in various situations, from emergencies when a patient’s airway needs to be protected, to regular use in the operating room. By ensuring a secure airway for proper oxygen flow and ventilation, the procedure can assist in patient resuscitation, reduce complications during or after surgery, and help critically ill patients get enough oxygen.