Atelectasis is caused by a blockage of the air passages (bronchus or bronchioles) or by pressure from outside the lung.
Here's a more detailed breakdown:
Atelectasis, a condition where all or part of a lung collapses, arises from two main categories of causes: obstruction (obstructive atelectasis) and compression (non-obstructive atelectasis).
Obstructive Atelectasis
This type occurs when something blocks the airways, preventing air from reaching the alveoli (tiny air sacs in the lungs). Air already present in these alveoli gets absorbed into the bloodstream, causing the alveoli to collapse. Common causes of obstruction include:
- Mucus plugs: This is a frequent cause, especially after surgery, in individuals with lung diseases like cystic fibrosis or asthma, or in patients who are weak and have difficulty coughing.
- Foreign objects: Small objects, especially in children, can be inhaled and lodge in the airways.
- Tumors: A tumor growing in the airway can block it.
Non-Obstructive Atelectasis
This type of atelectasis occurs when something outside the airways prevents the lung from inflating properly. Causes include:
- Pleural effusion: Fluid accumulating in the space between the lung and the chest wall compresses the lung.
- Pneumothorax: Air leaking into the space between the lung and chest wall can put pressure on the lung, causing it to collapse. This is different than atelectasis; however, pneumothorax can cause atelectasis.
- Tumors: A tumor outside the airway can compress the lung.
- Scarring (pulmonary fibrosis): Scar tissue can stiffen the lung, making it difficult to inflate.
- Surfactant deficiency: Surfactant is a substance that helps keep the alveoli open. A lack of surfactant, common in premature infants, can lead to atelectasis.
- Obesity: Increased weight on the chest can restrict lung expansion.
- Anesthesia: Anesthesia can change normal breathing patterns and affect gas exchange, which may lead to some degree of atelectasis.
It's important to distinguish atelectasis from pneumothorax. While both result in a collapsed lung, atelectasis involves a blockage or external pressure, whereas pneumothorax involves air leaking into the space around the lung.
In summary, atelectasis is a collapsed lung condition arising from either airway obstruction or external compression of the lung tissue.
