With Epiglottitis, “itis” means inflammation and epiglottis is a flap of elastic cartilage that sits at the top of the larynx or voice box. The epiglottis keeps food and liquid going down the esophagus and prevents it from going down the trachea by accident. So bacterial epiglottitis is when bacteria infect this flap of tissue and cause it to get swollen. This can be life threatening because it can flop down and block the trachea, making it impossible to breathe. This infection is actually thought to have been the cause of death for George Washington, America’s first president.
Now, the larynx is located in the bottom portion of the neck, just below where the pharynx splits into the trachea and the esophagus. The larynx is also called the voice box because it contains the vocal cords, which are two folds of mucous membrane that can open and close like curtains. Just like the rest of the respiratory tract, the walls of the larynx are made up of mucosal epithelium.
The epiglottis extends from the base of the tongue and anchors to the anterior rim of the thyroid cartilage, which is just in front of the larynx. The lateral borders of the epiglottis connect to the aryepiglottic folds, which have ligamentous and muscular fibers. This allows the epiglottis to act like a lid on a box and serve as the guardian of the airways. During swallowing, the epiglottis covers the larynx, preventing food and liquids from entering the airway; and during breathing, the epiglottis opens the larynx, allowing air to flow in and out.
Epiglottitis happens when the epiglottis, aryepiglottic folds, and other adjacent tissues become infected. Most commonly, epiglottitis is caused by Haemophilus influenzae, a gram negative rod bacterium, but in settings where Haemophilus influenzae type b vaccine is used commonly, other bacteria like Group A Streptococcus can also cause the infection. These bacteria are spread person-to-person by direct contact or through respiratory droplets that are created when people cough or sneeze.
Once the bacteria enter the body, they can get through the epithelial layer of the epiglottis. Immune cells in the epiglottic tissue detect the invading bacteria and release cytokines, like Tumor necrosis factor-alpha, or TNF-alpha. The cytokines cause blood vessels to become more permeable to fluid which results in local inflammation or swelling. As the inflammation gets worse, the swollen epiglottis starts to fatten up and block the larynx which obstructs airflow, and if the infection is severe, it can quickly lead to respiratory failure. In severe cases, respiratory failure can lead to a respiratory acidosis, which is a buildup of carbon dioxide in the blood.