Disease, Illness and Condition Library


    Atelectasis

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

    Atelectasis may be an acute or chronic condition. 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 (bronchietasis), destruction and
    scarring (fibrosis). People who smoke have a greater risk of developing
    atelectasis.

    Causes

    Atelectasis is most commonly caused by an obstruction of a large bronchus
    (one of the two main branches of the trachea leading directly to the lungs).
    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.
    Alternatively, the bronchus may be blocked by something pressing from the
    outside, such as a tumor, enlarged lymph nodes, or a significant amount of
    fluid (pleural effusion) or air (pneumothorax) in the pleural space. 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 and becomes infected.

    Atelectsis can occur in jet fighter pilots when the high forces generated by
    high speed flying close small airways. Atelictasis under these circumstances,
    sometimes described as acceleration atelectasis, leads to collapse of the
    alveoli in much of both lungs.

    Additionally, atelectasis can result if there is a shortage in the amount or
    effectiveness of the liquid substance (surfactant) that coats the lining of
    the alveoli. Usually, this liquid prevents the alveoli from collapsing.

    Acute Atelectasis: Acute atelectasis is a common postoperative complication,
    especially after chest or abdominal surgery. Acute atelectasis may also occur with
    an injury, sometimes described as massive, and involves most alveoli in
    one or more regions of the lungs. In these situations, 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
    (distention) 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 other factors that can limit
    chest movement, leading to shallow breathing, cause bronchial secretions to
    accumulate, preclude the lung from expanding fully, and suppress the cough
    reflex.

    In acute atelectasis that occurs because of a 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 present throughout both 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 atelctasis from excessive oxygen therapy and from mechanical ventilation,
    because of decreased effectiveness of surfactant. Another cause of acute
    atelectasis resulting from decreased effectiveness of surfactant is acute
    respiratory distress syndrome.

    Chronic Atelectsis: Chronic atelectasis may take one of two forms – middle
    lobe syndrome or rounded atelectasis. In middle lobe syndrome, the middle
    lobe of the right lung contracts usually because of 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 (folded lung syndrome), an outer portion of the lung
    slowly collapses as a result of scarring and shrinkage of the membrane layers
    covering the lungs (pleura). This produces a rounded appearance on 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 or the pleura.

    Symptoms

    The loss of functioning lung tissue leads to shortness of breath.
    The persistence of blood flow through the collapsed area leads to a decrease
    in the blood oxygen level – the heart rate increases, and sometimes the person
    may look bluish (a condition called cyanosis).

    The severity of symptoms depends on how rapidly the bronchus is blocked,
    how much of the lung is affected, what the precipitating factor was, and whether
    infection is present. When blockage happens swiftly and a lot of lung tissue is
    affected, a person may have sharp pain on the affected side, and have sudden
    and severe shortness of breath. The person may also experience shock with a
    severe drop in blood pressure; a rapid heart rate; a fever if infection develops.

    Widespread atelectasis resulting from deficient or ineffective surfactant
    produces shortness of breath; rapid, shallow breathing; a low blood oxygen
    level; and other symptoms depending on the cause of the acute lung injury
    (for example, fever and low blood pressure from sepsis) and any accompanying
    effects of low blood oxygen (such as abnormal heart rhythms) on organs other
    than the lung.

    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 ateletasis may have no symptoms, although
    some people with middle lobe syndrome have a hacking cough or develop
    pneumonia that resolves slowly or incompletely.

    Diagnosis

    Doctor’s 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 struggling with their breathing. When bronchial
    obstruction is suspected, computed tomography (CT), bronchoscopy, or both
    these tests may be performed to find the cause, especially when the collapse
    persists despite usual treatment measures.

    Prevention and Treatment

    People who smoke can decrease their risk of atelectasis after surgery by stopping
    smoking 6 to 8 weeks before an operation. After an operation, all people 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 stelectasis.

    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 positive 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.

    The primary treatment for acute massive atelectasis is correction of the
    underlying cause. A blockage that cannot be removed by coughing or by
    suctioning the airways often can be removed by bronchoscopy. Antibiotics are
    given for infection. Chronic atelectasis often is treated with antibiotics because
    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 treatment of atelectasis due to deficient or ineffective surfactant, attention is
    directed at treating the low blood oxygen (often with mechanical ventilation or
    positive end expiratory pressure) and its effects promptly and at identifying
    and treating the underlying condition. Treatment with a surfactant drug is
    lifesaving for premature babies with a surfactant deficiency. Such therapy
    is experimental in adults with the acute respiratory distress syndrome who
    have reduced surfactant activity.
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