What is Lung Atelectasis & What is its Pathophysiology?
What is Lung Atelectasis (LA)?
Lung Atelectasis also referred to as Atelectasis lung, occurs when a lung or its lobe partly or fully gives away (collapses) as a result of the shrinkage of the alveoli, which are the tiny air sacs, inside the lung. Lung atelectasis is a difficulty that affects the respiratory system after a surgery.
Lung atelectasis is also an impediment that could occur due to other issues affecting the respiratory system such as cystic fibrosis, foreign objects breathed into the lungs, tumors in the lung, immune weakness in the respiratory system and injuries to the chest.
It does not always involve the same amount of lung tissue and the amount varies depending on the source of lung atelectasis. The condition can result in breathing difficulties and reduced oxygen in the lungs especially where lung disease already exists. Treatment for Lung Atelectasis is administered based on the origin of the condition and the degree of collapse.
Lung Atelectasis can be acute or chronic and may cover a broad range of pathophysiologic changes from microatelectasis, which cannot be detected on a chest X-ray to macroatelectasis with loss of segmental, lobar, or overall lung volume. It is observed in people who are immobilized and have shallow monotonous breathing pattern. Lung Atelectasis is also observed in patients with chronic airway obstruction that blocks air flow to a location of the lung.
What is Obstructive Lung Atelectasis?
Obstructive lung atelectasis also known as Resorptive lung atelectasis as a result of a blocked airway. Air retained far from the obstruction is reabsorbed from the air sacs without air resulting in the collapse of the affected regions due to lack of gas. The degree of occurrence is dependent on a number of things especially the amount of collateral ventilation and the characteristics of the inspired gas.
What is Non Obstructive Lung Atelectasis?
Non obstructive lung atelectasis results from a contact failure between the visceral and parietal pleura, a loss of surfactant or the replacement of a normal lung parenchyma with scar tissue or infiltrating disease.
What is Round Lung Atelectasis?
Round lung atelectasis is also known as folded lung or blesovsky syndrome. It is a strange kind of lung atelectasis that occurs when the redundant pleura infolds. When the lung gives way (collapses), it can at times look like a mass.
Lung Atelectasis in Children
Lung atelectasis is a condition that causes a part of the lung or the entire lung to give way occurs randomly without being influenced by sex or race. It may, however, affect younger children more than older ones and adolescents. Lung atelectasis does not stay for very long in adults but in children it does linger. If it is widespread and patchy, it is very difficult to differentiate from pulmonary infiltration. Atelectasis of an entire lung or a lobe thereof is most often seen with asthma, viral lower respiratory tract infection, primary pulmonary tuberculosis and foreign bodies.
Pathophysiology of Lung Atelectasis
Lung atelectasis can be caused by 4 different things, which are as follows:
- Airways that may be blocked from the inside.
- Airways that may be blocked due to external compression.
- Compressed lung tissue.
- Alveoli that may fail to expand fully resulting in collapse.
The most common cause of lung atelectasis in children is the intrinsic air passage obstruction, where the airways are blocked from the inside of the lung. The other reasons could be swallowing disorder due to aspiration, endo bronchial tuberculosis, bronchiolitis, gastroesophageal reflux leading to aspiration, cystic fibrosis, and irregular air passage secretions for other causes.
Children below the age of 10 can easily develop lung atelectasis compared to older children because they rely on their feeding airways to get air into the alveoli as their inter airway canals of lambert or the inter alveolar pores of Kohn are still undeveloped.
External compression on the airways can be caused by enlarged lymph nodes, lymphoma or other tumors appearing in the chest. An enlarged heart can also compress the lung.
The alveoli may collapse in children who hypo ventilate for a long period. This can affect children with neuromuscular disease, those who have undergone surgery in the upper abdomen, those on medications that interfere with their ventilation such as narcotics and those with chest walls that are smaller than normal. Children sedated for CT or MRI may also develop lung atelectasis. This may be as a result of the inability to effectively clear the airway secretions due to an ineffective cough thus obstructing the airway. Atelectasis resulting from the density of lung tissue mostly arises from presence of air, blood, pus or chyle in the pleural space. Lung tissue can be compressed by abdominal contents, chest wall masses and abnormal chest wall. If a particular part of the lung enlarges, it may compress the adjacent lung causing lung atelectasis.
Lung Atelectasis Vs. Pneumothorax (Collapsed Lung)
Lung atelectasis occurs when the lung partially or fully collapses whereas pneumothorax or collapsed lung occurs when the pleural cavity has air. The pleural cavity lies between the lungs and the chest wall thus separating the two. Lung atelectasis mostly occurs after surgery due to the collapse of the alveoli whereas pneumothorax is a major cause of lung collapse. Lung atelectasis can occur when the air passages are blocked by mucous, tumors or foreign objects. In pre-term babies, it can result from the absence of surfactant. This is the liquid that covers the inside of the lungs and enables the air sacs to remain open. The lack of it causes the lung to collapse. It can also result from having fluid in the pleural cavity in pleural effusion.
On the other hand, pneumothorax or collapsed lung arises from injuries to the chest wall either from a knife, sharp instrument of puncture from a fractured rib. In slim people who are also tall, blebs/blisters which are small sacs filled with air rupture and air gets into the pleural cavity resulting in spontaneous pneumothorax. Asthma, pneumonia and tuberculosis among others can cause damage to the lungs thus causing pneumothorax or collapsed lung. Drug abuse and smoking are the risk factors.
In summary, lung atelectasis results when the lung or a portion of it collapses; the air sacs collapse in this case whereas in pneumothorax or lung collapse, the pleural cavity gets air. Chest X-ray and CT scan help diagnose the conditions. Chest physiotherapy helps in Atelectasis whereas in pneumothorax a tube is inserted in the chest and the underlying cause is treated. Lung atelectasis is the collapse of the aerated lung. Most often it is caused by internal bronchial obstruction of the air flow, but it may result from external compression of the lung, such as by empyema, mesothelioma or by internal compression.