Atelectasis

Overview

Atelectasis is a condition in which all or part of a lung becomes airless and contracts.

• Atelectasis may be acute or chronic.
• In acute Atelectasis, the lung has recently collapsed and is primarily notable only for airlessness.
• In chronic Atelectasis, the affected area is often characterized by a complex mixture of airlessness, infection, widening of the bronchi (bronchiectasis), destruction and scarring.
• People who smoke have a greater risk of developing Atelectasis.

Causes

• The most common cause is an obstruction of a large bronchus.
• Smaller airways can also become blocked.
• The obstruction may be caused by a plug of mucus, a tumor, or an inhaled foreign object inside the bronchus.
• Bronchus may also be blocked by something pressing from outside such as a tumor, enlarged lymph nodes, or a significant amount of fluid (pleural effusion) or air in pleural space (pneumothorax).
• When an airway becomes blocked, the air in the small air sacs of the lung (alveoli) beyond the blockage is absorbed into the bloodstream, causing the alveoli to shrink and retract.
• The collapsed lung tissue commonly fills with blood cells, serum and mucus become infected.
• Atelectasis can occur in jet fighter pilots when the high forces generated by high speed flying close small airways.
• Atelectasis of this type is described as acceleration atelectasis, leading to the collapse of alveoli in a large portion of both the lungs.
• Additionally, atelectasis can result if there is a deficiency in the amount of effectiveness of surfactant (liquid) that coats the lining of the alveoli.
• Under normal circumstances, this liquid prevents the alveoli from collapsing.

Acute Atelectasis

• It is a common postoperative complication, especially after abdominal or chest surgery.
• It may also occur due to an injury of the chest; the causes of the later may be an accident, fall or stabbing.
• Sometimes, atelectasis after an injury or surgery is massive and involves most alveoli in one or more regions of the lungs.
• In these circumstances, the degree of collapse among alveoli tends to be quite consistent and complete.
• Large doses of opioids or sedatives, tight bandages, chest or abdominal pain, abdominal swelling and immobility of the body increase the risk of acute atelectasis following surgery or injury, or even spontaneously.
• Certain neurologic conditions and chest deformities are additional factors that lead that can limit chest movement, lead to shallow breathing, cause bronchial secretions to accumulate, preclude the lung from expanding fully, and suppress the cough reflex.
• In acute atelectasis that occurs before the deficiency in the amount or effectiveness of surfactant, many but not all alveoli collapse, and the degree of collapse is not uniform.
• Atelectasis in these circumstances may be limited to only a portion of one lung, or it may be present throughout both the lungs.
• When premature babies are born with surfactant deficiency, they always develop acute atelectasis that progresses to neonatal respiratory distress syndrome, unless they are treated with replacement surfactant.
• Adults can also develop acute atelectasis from excessive oxygen therapy and from mechanical ventilation, because of decreased effectiveness of surfactant.
• Another cause of acute atelectasis resulting from the decreased effectiveness of surfactant is acute respiratory distress syndrome.

Chronic Atelectasis

• It may take one of two forms: middle lobe syndrome or rounded atelectasis.
• In middle lobe syndrome, middle lobe of the right lung contracts, usually because of the pressure on the bronchus from enlarged lymph glands and occasionally a tumor.
• The blocked, contracted lung may develop pneumonia that fails to resolve completely and leads to chronic inflammation, scarring, and bronchiectasis.
• In rounded atelectasis or folded lung syndrome, the outer portion of the lung slowly collapses as a result of scarring and shrinkage of the membrane layers covering the lungs.
• This produces a rounded appearance on an x-ray that doctors may mistake for a tumor.
• Rounded atelectasis is usually a complication of asbestos-induced disease of the pleura, but it may also result from other types of chronic scarring and thickening of the pleura.

Symptoms

• Shortness of breath due to the loss of functioning of the lung tissue.
• Increased heart rate and bluish appearance (sometimes) of the person due to persistent blood flow through the collapsed area leading to a decrease in blood oxygen level.
• The severity of symptoms depends on
  • How rapidly the bronchus is blocked.
  • How much of the lung is affected?
  • Precipitating factor.
  • Presence or absence of infection.
• When blockage happens quickly and a lot of lung tissue is affected, the person may become blue or ashen in color, have a sharp pain on the affected side and have sudden and extreme shortness of breath.
• The person may also experience shock with a severe drop in blood pressure, a rapid heart rate, and fever if infection develops.
• Widespread atelectasis resulting from deficient or ineffective surfactant produces shortness of breath, rapid and shallow breathing, low blood oxygen levels and other symptoms depending on the cause of the acute lung injury. For example, fever and low blood pressure from sepsis and accompanying effects of low blood oxygen (such as abnormal heart rhythms) on organs other than lungs.
• Slowly developing atelectasis may cause no symptoms or only minor ones such as shortness of breath or an increased heart rate.
• People with middle lobe syndrome and rounded atelectasis may have no symptoms, although some people with middle lobe syndrome have a hacking cough or develop pneumonia that resolves slowly or incompletely.

Diagnosis

• Doctors suspect atelectasis based on a person's symptoms, the physical examination findings, and the setting in which the symptoms occurred.
• A chest X-ray that shows the airless area confirms the diagnosis, but the X-ray may appear normal even when the person is feeling breathless.
• When a bronchial obstruction is suspected, computed tomography, bronchoscopy, or both these tests may be performed to find the cause, especially when the collapse persists despite usual treatment measures.

Prevention

• People who smoke can decrease their risk of atelectasis after surgery by stopping smoking 6 to 8 weeks before an operation.
• After the operation, everyone should be encouraged to breathe deeply, cough regularly, and move about as soon as possible.
• The use of breathing devices to encourage voluntary deep breathing(incentive spirometry) and certain exercises, including changing position to increase the drainage of lung secretions, may help to prevent atelectasis.
• People with chest deformities or neurologic conditions that cause shallow breathing for long periods may benefit from mechanical devices that assist their breathing.
• One method is continuous airway pressure, which delivers oxygen through a nose or face mask to help ensure that the airways do not collapse, even at the end of a breath.
• Sometimes additional respiratory support is needed with a mechanical ventilator.

Treatment

• The primary treatment for acute massive atelectasis is the correction of the underlying cause.
• A blockage that can not be removed by coughing or by suctioning the airways often can be removed by bronchoscopy.
• Antibiotics are given for an infection.
• Chronic atelectasis is often treated with antibiotics because an infection is almost inevitable.
• In certain cases, the affected part of the lung may be surgically removed when recurring or chronic infections become disabling or bleeding is significant.
• If a tumor is blocking the airway, relieving the obstruction by surgery, radiation therapy, chemotherapy, or laser therapy may prevent atelectasis from progressing and recurrent obstructive pneumonia from developing.
• In the treatment of atelectasis due to deficient or ineffective surfactant, attention is directed at treating the low blood oxygen levels. This is often done with mechanical ventilation or positive end expiratory pressure. This effects promptly and at identifying and treating the underlying condition.
• Treatment with surfactant drug is life-saving for premature babies with a surfactant deficiency. Such therapy is experimental in adults with acute respiratory distress syndrome who have reduced surfactant activity.

Causes of Obstructive Atelectasis

Mucus plug
Accumulation of mucus in the airways is a common cause. This occurs in many patients during and after surgery because the patient cannot cough. Also, the drugs given during surgery make the lungs inflate less fully than usual, so normal secretions collect in the airways. Suctioning the lungs during surgery helps clear away these secretions, but they may continue to build up afterward. Mucus plugs are also common in children, people with cystic fibrosis and during severe asthma attacks.
Foreign body
Obstruction of airways is common in children who have inhaled an object, such as a peanut or small toy part, into their lungs.
Narrowing of major airways from disease
This may occur due to chronic infections, including fungal infections, tuberculosis and other diseases.
This can scar and constrict major airways.
Tumor in a major airway
Tumor growth in an airway can narrow it and can create a partial or complete blockage of the airway.
Blood clot
Blockage due to blood clot occurs only if there's significant bleeding into the lungs that can't be coughed out.
This is often observed in patients who have suffered serious injury due to an accident or an impact with a solid object (severe impact).

Causes of Non Obstructive Atelectasis

Injury
Chest trauma from a fall or car accident can cause a person to avoid taking deep breaths due to the pain, which may lead to compression of the lungs.
Pleural effusion
This is a buildup of fluid between the tissues (pleura) that line the lungs and the inside of the chest wall.
Pneumonia
Different types of pneumonia or an infection of the lungs may temporarily cause atelectasis.
Pneumothorax
This is the condition in which air leaks into the space between the lungs and the chest wall, indirectly causing a part of lung or the entire lung to collapse.
Scarring of lung tissue
Scarring could be caused by injury, lung disease or surgery. In these rare cases, the atelectasis is minor compared with the damage to the lung tissue from the scarring.
Tumor
A large tumor can press against and deflate the lung, as opposed to blocking the air passages.

Risk Factors

• Age: especially younger than 3 or older than 60 years of age.
• Any condition that interferes with spontaneous coughing, yawning and sighing.
• Confinement to bed with infrequent changes of position.
• Impaired swallowing function, particularly in older adults. Aspirating secretions into the lungs is a major source of infections.
• Lung disease, such as asthma in children, COPD, bronchiectasis or cystic fibrosis.
• Premature birth.
• Recent abdominal or chest surgery.
• Recent general anesthesia.
• Respiratory muscle weakness, due to muscular dystrophy, spinal cord injury or another neuromuscular condition.
• Any cause of shallow breathing including medications and their side effects, or mechanical limitations, such as abdominal pain or rib fracture.

Types Of Atelectasis

Linear Atelectasis

Linear atelectasis is said to occur when a portion of the lungs away from bronchus has collapsed and the collapsed portion is all joined together.

Bibasilar Atelectasis

Bibasilar atelectasis is a condition in which lungs get partially collapsed.

Subsegmental Atelectasis

Subsegmental atelectasis is defined as the decrease in the volume of lung due to an impediment of the small or subsegmental bronchus. The condition appears as linear opacity in chest radiograph. This is also known as plate-like atelectasis or discoid atelectasis.  In a chest x-ray, discoid atelectasis will show up as a disc or plate-like shadow on the lungs. This disc may be linear or horizontal in position. Discoid or Plate atelectasis is diagnosed and treated in much the same way as other types of atelectasis.

Compressive Atelectasis

Compressive atelectasis develop when a person’s lungs cannot inflate fully due to any space occupying lesion. The lesion impinges upon the lungs and limits the volume of air that the patient can inhale with a given breath.

Minimal Dependent Atelectasis

Minimal dependant atelectasis is a problem in which only a small portion of your lung collapses and therefore, it is not as serious as regular atelectasis. This condition usually affects the alveoli in the lower part of your lungs.

Dependent Atelectasis

Dependant atelectasis or gravity dependant atelectasis is a relatively benign form of atelectasis that usually requires no treatment. It is caused by small areas of the lung being unable to expand fully when a person is lying down. The small portion of the lung that collapses under the influence of gravity usually re-expands on its own when a person stands up or changes his position. It is usually detected during a CT scan of the chest.

Resorptive Atelectasis

This type of atelectasis is caused by the obstruction in the airways.

Relaxation Atelectasis

This type of atelectasis occurs in patients with pneumothorax and pleural effusion.

Adhesive atelectasis

In this type of condition, the alveoli in the lungs are kept open due to reduced surface tension.

Fibrosis atelectasis

Fibrosis of the lungs means scarring of the lung tissue.  If a person is suffering from atelectasis, then the resulting complications can cause fibrosis. Fibrosis is tissue that heals. Though the scarring heals, the scars remain in the tissue. This scarring further prevents the atelectasis from healing.

Round Atelectasis

In this type of condition, the affected lung is devoid of air due to pleural disease.

Cicatricial Atelectasis

This type of atelectasis occurs when the alveoli gets trapped in scar tissue and causes a collapse in the lungs.