Mucociliary, a portmanteau of “mucous” and “ciliary,” describes the specialized epithelial membranes lining the airways. These membranes include numerous fine hairs, known as cilia, along with mucus-producing cells, which coat the cilia in a thin layer of fluid. The mucus traps particulates when they enter the airways, and the cilia transport the foreign material safely away, before it has a chance to enter the lungs and cause disease. In some special cases, as in cystic fibrosis, patients produce too much mucus and this may clog the airways.
The mucociliary membranes are part of the immune system's defense against hostile organisms and they are very important for airway health. If the numbers of hairs decline, the environment gets too dry, or the motion of the cilia declines, people are more at risk of infection and other health problems. People who smoke or work in environments with toxic substances are more at risk of developing problems with these membranes, along with people in extremely dry climates.
The process of trapping and moving particulates is known as the mucociliary elevator or transport system. Bacteria, viruses, and materials like pollen will all sink into the mucus along the airways when people inhale, rather than being carried into the lungs. The cilia beat steadily to push these materials up toward the mouth. People can either swallow them when they gulp down secretions, or may cough them up if they are producing a lot of mucus, as in the case of someone with lung or airway irritation caused by inflammation or infection.
Trauma to the airways can damage the mucociliary system. Intubation, where care providers insert a tube into the trachea to secure the airway, can potentially injure the airways, as can activities like scoping to collect material for medical diagnosis. Doctors exercise care during procedures when they need to enter the airways and only do so when the benefits outweigh the risks; intubation, for example, can save a patient's life by ensuring he gets enough oxygen.
Lesions in the airways associated with cancers and other problems can also interfere with the mucociliary elevator. This will make it more difficult for people to prevent and fight off lung infections. In people with compromised immune systems, this increases the risk of problems like pneumonia. Some patients have trouble coughing up or swallowing secretions and may need to use a suction device periodically to keep their airways clear, as otherwise they could experience difficulty breathing.