Atelectasis

Atelectasis is a condition in which a small or large area of lung tissue collapses, resulting in decreased exchange of gases within the lungs. It occurs when the alveoli, small air sacs  that line the lung, collapse. Alveoli are located at the end of each bronchiole, which are small branches off of the bronchi, or air tubes. The alveoli are the site of gas exchange in the body, allowing oxygen to enter the blood and carbon dioxide to exit. Usually, they are lined with surfactant, which is a liquid layer that prevents the alveoli from collapsing. 

Atelectasis is a common complication after surgery and can also occur as a result of other conditions. If left untreated, atelectasis may be life threatening. 

Atelectasis can be categorized as obstructive or nonobstructive. Obstructive, also called resorptive, atelectasis is when something physically blocks the airway and causes reabsorption of the air (carbon dioxide and oxygen) from the alveoli with subsequent collapse of that portion of the lung. On the other hand, nonobstructive atelectasis refers to all other types that are not associated with an obstruction. Types of nonobstructive atelectasis include compressive, contraction, and adhesive atelectasis. Compressive atelectasis occurs when something pushes on and compresses the lungs. Contraction atelectasis is due to scar tissue, or fibrosis, interfering with alveoli expansion and contraction. Finally, adhesive atelectasis occurs when there is a loss of surfactant on the alveoli. 

Depending on the type, atelectasis can result from a variety of different causes. Obstructive atelectasis may be caused by anything blocking the alveoli, like a build up of mucus (i.e., mucus plug), a foreign body (e.g., food particles or small toys), or a tumor. A mucus plug can form due to conditions that increase mucus production, such as chronic obstructive pulmonary disease (COPD) or cystic fibrosis. 

The most common cause of nonobstructive atelectasis is anesthesia because it reduces surfactant and decreases alveolar volume. 

Compressive atelectasis may result after a diaphragmatic hernia, when a part of an organ from the abdominal cavity goes into the chest cavity, near the lungs. Additionally, compressive atelectasis may occur when there is fluid or air in the lungs, also known as pleural effusion or pneumothorax. 

Contraction atelectasis may be caused by scar tissue in people with chronic lung diseases like tuberculosis or sarcoidosis. 

Meanwhile, adhesive atelectasis has many causes, including surfactant deficiency, which may result in respiratory distress syndromes in adults and newborns.

Risk factors for atelectasis include any underlying lung, neuromuscular, or chronic systemic disease. Advanced age, obesity, or a history of smoking can also increase the risk of atelectasis. In the case of atelectasis caused by anesthesia, the type of surgery and anesthesia may correspond to varied risks. 

Signs and symptoms of atelectasis often depend on the severity of the condition. If only a small area of the lung is affected, one might experience no symptoms at all. In more severe cases, individuals may feel short of breath, cough, or have chest pain. Additionally, individuals may experience fast, shallow breathing or a faster heart rate. Due to decreased oxygen levels, some people may notice cyanosis, which is a bluish discoloration on parts of the skin. In many cases, the individual may also experience decreased chest expansion when breathing, particularly on the side with the atelectasis. 

Atelectasis can be difficult to diagnose and may require several other diagnoses to be ruled out first. A history of signs and symptoms for atelectasis will usually be assessed, along with a physical examination. In the physical exam, a clinician may notice chest wall expansion, decreased or absent breath sounds, decreased vibration while speaking (i.e., tactile fremitus), a dull sound when tapping fingers on the area of atelectasis, and sometimes, crackling sounds while breathing (i.e., basilar rales). After the physical exam, a chest X-ray is often needed to confirm the diagnosis and determine the cause of the atelectasis. This allows for visualization of lung abnormalities, like the collapsed lung. The chest X-ray may help to rule out pneumonia or other possible causes of low oxygen. In most cases affecting adults, atelectasis will appear in the lower left lobe of the lungs. In some cases, magnetic resonance imaging (MRI) or ultrasound imaging will also be used to diagnose atelectasis. 

Treatment for atelectasis depends on the cause, type, and severity. Atelectasis occurring within 24 hours after a surgery will often resolve with conservative interventions that are similar to prevention techniques (e.g., deep-breathing exercises). If a person is experiencing low oxygen levels, they may be given oxygen via a mask or a nasal cannula, which is a small plastic tube with two prongs that rest inside the nose. When atelectasis is caused by a mucus plug, the mucus can be suctioned out by a bronchoscopy, a thin flexible tube that is inserted into the bronchi to suction out the mucus. Nebulized bronchodilators (liquid mist to open the airways) may also be added to treatment regimens in order to keep the airway open. More extensive treatment --, such as surgery, radiation, or chemotherapy -- may be required if lung cancer or other lung disease caused the atelectasis. With adequate and timely treatment, the lung can return to an expanded state with few complications.

Atelectasis refers to the collapse of alveoli in the lungs. It most commonly occurs after surgery and the use of general anesthesia. Types of atelectasis are generally classified as obstructive or nonobstructive. If a person presents with symptoms of atelectasis, they often have decreased oxygen levels, shortness of breath, and fast respiratory rates and heart rate. Diagnosis is usually made after a chest X-ray is performed. Treatment varies depending on the cause and severity of the atelectasis and may include administering oxygen, clearing mucus with a bronchoscopy, or maintaining an airway with nebulizers. Atelectasis may be prevented by chest physical therapy or deep-breathing exercises.