The upper airways. II. The larynx and trachea.
The laryngotracheal airway is the bottleneck of the respiratory system. Whereas disease in the nose or in the bronchial airways will affect respiratory airflow in a limited way, laryngotracheal disease must always be considered potentially life threatening. The nasal airway is the normal access to the lungs. As such, it serves vital functions in modifying the condition of ambient air before its access to the lungs. Impairment of the efficacy of nasal function in that regard will inevitably cast an unaccustomed burden on the lower airways and may possibly play a role in the long-term development of small airway disease in the lungs. When the nose is bypassed, acutely, as in orotracheal intubation, or chronically, as in tracheostomy or the laryngectomee, the pulmonary airways inevitably suffer. Attempts to substitute for the nose by humidification of inspired air are essential, but our current methods are not free of hazard and are of questionable efficacy. A better understanding of upper airway function and the injury resulting from malfunction or conducting ambient air directly to the trachea is now within our grasp but is not yet fully realized.