Guide To The Causes And Risk Factors Of Atelectasis

Atelectasis is a condition where a lobe of the lung or the entire lung collapses (partially or completely). This malfunction occurs when the alveoli or small air sacs contained with the individual's lung fill with fluid or become deflated. This condition makes it difficult for the affected individual to breathe, causes them to cough and wheeze, it and may result in rapid or shallow breathing. When part or all of a lung collapses, it cannot effectively get oxygen to the alveoli and can result in hypoxemia or low blood oxygen levels. Atelectasis also increases the risk of mucus accumulation in the lung, resulting in pneumonia. This condition is diagnosed using an oximetry test, bronchoscopy, CT scan, and thorax ultrasound. The way atelectasis is treated depends on what its underlying cause is. Mild cases may not require treatment, while severe cases necessitate surgery.

Foreign Body Inhalation

Many cases of atelectasis are the result of foreign body inhalation. When an object is inhaled into the lung, the individual's bronchus or bronchiole can become obstructed. The alveoli usually fill up with air that contains oxygen and nitrogen the individual has inhaled, and the constant exchange of gases allows for the alveoli to keep their shape. When an individual inhales a foreign object, the oxygen and nitrogen inside the alveoli, which are located behind the blockage in the air pathway, are eventually all absorbed into the bloodstream. The alveoli function similar to how a balloon works. When there is no more air in the alveoli, they shrink, shrivel, and ultimately collapse into themselves. When numerous alveoli collapse, the patient's lung loses volume. The foreign body is often a piece of food, a toy, or a pill that has gone into the respiratory tube rather than down the esophagus. The most common cases of obstructive atelectasis that occur due to foreign body obstruction occur in infants, toddlers, and young children who put objects into their nasal cavities or their mouth. Many cases of foreign body precipitated atelectasis are the result of elderly or ill individuals who aspirate a piece of food.

Tumor In The Airway

Some cases of atelectasis are caused by a tumor in the airway of an affected individual. The type of atelectasis is described using the term compressive atelectasis, which can be the result of a cancerous or benign tumor or growth inside of, or directly adjacent to, airways within the lung. When a tumor grows in an individual's lung and slowly causes the compression of one or more of its containing airways, the balance of gas exchange in the alveoli will be disrupted. Healthy individuals breathe oxygen and nitrogen into the trachea, through the bronchi and the further branched off bronchioles, then into the alveoli. The blood in small capillaries in the alveoli absorbs the oxygen and releases carbon dioxide. When there is a tumor or growth inside of, or adjacent to, one of the airways in the lung, it will slowly start to close up. As the airway becomes increasingly narrow, the amount of inhaled air that reaches the following alveoli will be less than the amount of air the blood is absorbing. Eventually, the alveoli do not have enough air and ultimately collapse in on themselves. This type of atelectasis gradually develops over time as numerous alveoli collapse, and the lung loses its volume.

Mucus Plug

Atelectasis may be caused by a mucus plug that has formed inside an individual's lung. A healthy individual has a certain amount of mucus the lungs produce to carry out normal immune defense processes. Mucus is a blend of water, lipids, mucins, ions, and proteins. When an individual has lungs that abnormally produce an excessive amount of mucus, or that produce abnormally thick and sticky mucus, they can develop a mucus plug in the lung. The mucus plug causes a blockage in the airways that results in obstructive atelectasis. One of the most common causes for a mucus plug in the airway is attributed to patients who have recently undergone a surgical procedure. The anesthesia used during surgery causes the lungs to increase their bronchial mucus secretions. An individual who has undergone abdominal surgery will also experience shallow breathing and weakening of the muscles that control the lungs. A combination of the excess mucus production and weakened muscles can allow for a mucus plug to form large enough to obstruct the airway. Patients affected by cystic fibrosis, chronic obstructive pulmonary disorder, asthma, pneumonia, bronchitis, and several other conditions are at a higher risk of experiencing atelectasis caused by a mucus plug.

Chest Trauma

Anyone who has experienced chest trauma is at a greater risk of developing atelectasis. There are several mechanisms that cause an increase in risk. When an individual experiences severe blunt trauma to their chest, such as from a car collision or high fall, tissue injury can cause blood and proteins to leak into the airways supplying the alveoli. These substances obstruct the airway, effectively stopping the alveoli from receiving inhaled air. Swelling as a result of general chest trauma can cause tissues in the lung to compress against each other and stop the flow of air to the alveoli. Blunt trauma to the chest causes the alveoli in the area to become unstable and at a greater risk of collapsing. An individual who has experienced chest trauma that has formed significant scarring inside of the lungs can develop obstructive atelectasis when the scar tissue obstructs an airway. Penetrating trauma to the chest can cause a leakage of air out of the lung, causing the alveoli to collapse due to an absence of air. Chest trauma can cause fluids or blood to leak into the membrane that surrounds the lungs, causing an increase of external pressure on the lungs. The external pressure compresses the airways and can cause an obstruction. Patients taking respiratory suppressing pain medications during trauma recovery, or who have had surgery to treat their trauma are at a higher risk of atelectasis.

Pneumonia

Pneumonia patients are at a higher risk of developing atelectasis. Pneumonia is an infection that affects an individual's lungs and causes inflammation and the collection of pus or fluid in the lung. It can be caused by viruses, bacteria, or fungi. One mechanism of how pneumonia precipitated atelectasis occurs is a when pus accumulates in a lung cavity that forms a lung abscess and causes an obstruction in one of the airways. Pneumonia can also cause fluid to accumulate in the thin space between the membrane layers that line the chest cavity and lungs. The fluid builds up and places external pressure on the lungs, which compresses the airways. This condition also makes it very difficult for a patient to breathe normally and take deep breaths. When an individual cannot breathe in enough air to reach the air sacs in the bottom of the lungs, it is called shallow breathing. When air is unable to reach the bottom of the lungs in pneumonia patients, the alveoli shrink and collapse, causing a decrease in lung volume and atelectasis in the bottom lobe of the lung.