Mucociliary clearance in health and disease

Summary

Pulmonary defence mechanisms are so effective that they maintain a relatively sterile environment in the lungs below the level of the larynx.

The upper respiratory tract defences include nasal vibrissae, the nasal turbinates and the epiglottis which all function to prevent the inhalation and aspiration of unwanted particles into the lungs.

The lower respiratory tract defence mechanism is provided by the mucociliary escalator.

Ciliated epithelium extends from the trachea down as far as the respiratory bronchioles. These cilia are bathed in fluid and beat in a co-ordinated manner, moving mucus that has trapped inhaled dust and debris towards the mouth where it is either swallowed or coughed and cleared.

There are three components necessary to ensure optimal functioning of the mucociliary escalator:

• Ciliated epithelium
• Aqueous sol layer
• Gel or mucous layer

Various conditions that effect these individual components (eg. dyskinetic cilia, dehydration and hypersecretory conditions) which will impact on mucociliary clearance, potentially leading to an accumulation of secretions within the airway. This may in turn result in airway obstruction, increased work of breathing and the development of a chest infection.

Physiotherapists have several treatment techniques and modalities available to them to assist with the mobilisation and clearance of retained secretions.

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