Which condition can lead to atelectasis?

Atelectasis refers to the collapse or incomplete expansion of the lung or a section of the lung, which can result from various conditions. When considering the option of a tumor mass, this is particularly relevant because a tumor can obstruct the airways. When an airway is blocked by a tumor, it can prevent air from reaching the alveoli (the tiny air sacs in the lungs), leading to a decrease in lung volume in the affected area. This obstruction causes the alveoli to collapse, resulting in atelectasis.

The role of a tumor mass in causing atelectasis is significant because tumors can be located in various parts of the respiratory tract. For example, a tumor in the bronchus can easily obstruct airflow and lead to collapse of the lung segment supplied by that bronchus.

In contrast, while other options may relate to respiratory issues, they do not directly lead to atelectasis in the same manner. Pneumonia often leads to consolidation rather than collapse of the lungs, thrombi primarily affect blood circulation and not air passage directly, and pneumothorax involves air in the pleural space that might lead to lung collapse but through a different mechanism. Thus, a tumor mass is the most direct cause of atelectasis due to