Our airways have a good filtering and cleaning mechanism: The entire respiratory tract is covered with a mucous membrane and fine hairs called cilia. Foreign bodies such as viruses and bacteria stick to the protective film of the mucous membrane and are transported towards the throat by coordinated movements of the cilia.
When foreign bodies are very small and succeed in reaching the smallest ramifications of the lung, the alveoli, the lung is cleaned by macrophages. Macrophages are an element of our immune system and are also called scavenger cells. They can detect non-specific foreign bodies and pathogens, absorb them and finally break them down and render them harmless with enzymes.
But the cleaning mechanism of the airways can be disrupted in various ways:
- The mucous membrane becomes too dry. This happens particularly often in winter due to the warm, dry air from heating systems. Then, when the protective film of moisture is gone, viruses and bacteria can reach the mucosal cells more easily and cause you to catch a cold. This is why in winter it is recommended to inhale isotonic saline solution to prevent a cold. The airways are moistened and the removal of pathogens is supported.
- Too much mucus has formed. The fine hairs are not able to remove viruses and bacteria as effectively any more. In this case, inhaling hypertonic saline solution can help to liquefy the mucus, lending support to the natural cleaning mechanism of the airways.