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Why do we have sinuses? They act as a humidifier, play a role in immune response and make the head lighter. They are a reservoir for nitric oxide (NO). Any cavity needs to ventilate and drain, so cilia motility is very important.
Nitric oxide
NO is released in the nasal airways.
There are high NO levels in the paranasal sinuses as these cavities function as reservoirs for NO. In inspiration through the nose, this NO will follow the airstream to the lower airways and the lungs. Nasally derived NO has been shown to increase arterial oxygen tension and reduce pulmonary vascular resistance, thereby acting as an airborne messenger. Chronic sinusitis is associated with more than a 50% reduction in nasal NO levels.
Mucociliary clearance (MCC)
MCC is one of the most important nonspecific defence mechanisms of the respiratory tract. Its impairment is a well-documented feature of chronic respiratory diseases. Mucociliary apparatus consists of three functional compartments:
- The cilia
- A protective mucus layer
- An airway surface liquid (ASL) layer.
Several inflammatory mediators influence the mucociliary apparatus.
Mucociliary escalator
Approximately 20-30ml of secretions are produced by the airways every day. This is necessary to protect the airway from foreign particles. This is cleared by the muco-ciliary escalator and swallowed. If mucus exceeds this amount, a cough is necessary to clear the airways.
The mucociliary escalator covers most of the bronchi, bronchioles, and nose, and is composed of two basic parts:
- Mucous producing goblet cells
- Pseudo stratified columnar epithelium.
Mucous secretional system
The mucous blanket is primarily composed of mucoglycoproteins, which provide protection against:
- Low humidity
- Cold weather
- Foreign substances and bacteria
- Immunoglobulin G and interferon, as well as other inflammatory cells, are present in sinonasal secretions to provide an antiviral role.
Treatment goals
- Managing the inflammation (getting rid of all the inflammatory cells).
- Restoring the mucociliary clearance:
- Natural mucous membrane hydration (ASL)
- The ciliary function (CBF)
- Getting rid of the mucous and bacteria/biofilms.
Efficacy of decongestant therapy
There is no value in the use of systemic decongestants during the management of sinusitis. In South Africa, more than 24M units of systemic decongestants were sold in 2020 alone. It dehydrates the nasal mucosa rendering the cilia ineffective and creates the ideal environment for the formation of a bacterial biofilm and secondary bacterial infection.
The importance of mucociliary clearance
The most appropriate therapeutic approach for the prophylaxis and primary management of sinusitis is the maintenance of an efficient mucociliary transport system:
- Hydrate the airways
- Increase airway surface liquid depth
- Enhance ciliary beat frequency.
