You can really understand sinusitis only if you understand muco-ciliary movement!
Yes, muco-ciliary movement is the cornerstone of the respiratory tract health, including upper nose, sinuses and lower bronchioles.
Muco-ciliary movement includes two parts--mucus and cilia. The lining cells of the respiratory tract secrets mucus continuously onto the surface of the lining cells of the respiratory tract; and the cilia, protruding from the lining cells, move the mucus toward specific direction by its to and fro action at frequencies from 8cps~15cps. There is around 1 liter of nasal/sinus clear mucus secretion per day in an adult, and there are millions of tiny cilia on the superficial lining cells in the nasal chamber and sinuses. These cilia move the nasal/sinus secretions backward from nasal chamber to the nasopharynx, throat and finally stomach. The above nasal mucus secretions and ciliary movement constitute the muco-ciliary movement.
The relationships between nasal chamber and para-nasal sinuses look like the river (nose) and surrounding lakes (sinuses). The sinus secretions flow into the nasal chamber via the sinus ostium and osteo-meatal complex ( an auto-controlled isthmus which can prevent the reflux of nasal chamber fluid back into the sinuses), just like the water in the lakes will flow into the river via a narrow but auto-controlled isthmus (ostium of the sinus), but the water in the river cannot flow into the lakes through the auto-controlled isthmus in normal condition. If the tenacious pus in the nasal chamber was forced into the sinuses by forceful nose-blowing but cannot flow out via the narrow sinus ostium by the muco-ciliary movement (just like some garbage in the river was squeezed through the isthmus into the lakes but was blocked to flow out by the narrow isthmus), or the auto-controlled isthmus was damaged ( like swelling of the sinus ostium) to stop the water drainage from the sinuses (just like the water in the lakes cannot flow smoothly into the river through the isthmus due to isthmus obstruction, resulting the water stasis in the lakes), then sinus inflammation with secondary bacteria infection happened (static water will become dirty and foul smelling).
The muco-ciliary movement in the human respiratory tract is an unbelievable fluid transport system -- an antigravity fluid transport system. Fluid always flows from higher position downward to lower position by gravity and cannot flow from lower position upward to a higher position. However the respiratory tract secretions can be moved toward a specific direction by this amazing muco-ciliary movement. The opening of the maxillary sinus is located at the upper part of the sinus, but the secretions at the floor of the sinus cavity can be moved upward (anti-gravity movement just like a lot of ants arrayed on the wall move their foods form the floor onto the roof) toward the upper sinus opening and then moved through the auto-controlled isthmus into the nasal chamber. This amazing antigravity fluid transport system in the human respiratory system -- the muco-ciliary movement plays the cornerstone role in the nasal/sinus self-protective mechanism. If this anti-gravity muco-ciliary movement is out of order, the secretions in the sinuses will be accumulated in the sinus floor -- an important diagnostic clue of sinusitis by sinus X-ray or CT scan, where we can find an air-fluid level in the sinus cavity instead of air only in the sinus cavity ( the sinus X-ray or CT scan can not detect the normal mucus layer on the lining cells of the sinus).
The muco-ciliary movement keeps the sinus health by removing the invading airborne bacteria, virus or other tiny particles trapped in the nasal mucus. If the virulence or amounts of invading viruses are over the clearing capability of the muco-ciliary movement or if the muco-ciliary movement is impaired by other reasons, rhino-sinusitis with secondary bacteria infection might be happened. The most important pathologic finding of rhino-sinusitis is impairment of the sinus muco-ciliary movement but not the bacteria infection. That's why you can not rely only antibiotics to successfully treat the sinusitis. Let me explain in a simple way, how will you clean a gutter filled with garbage and leaves? Use a lot of detergents or antiseptic chemical products? Or remove the garbage and leaves by broom and clean by water hose? Yes, you are right! Remove the leaves by water is easier and more effective than the chemical antiseptic products. That's why the best way to keep sinus health is to remove the pus and invading irritants by pulsatile nasal irrigation and resume the normal protective muco-ciliary movement. It's the basic concept of MMT (Maximal Medical Therapy) for chronic rhino-sinusitis, and our Sanvic way to stop rhino-sinusitis.