Several theories have tried to explain the relationship between SDB and nasal obstruction. Of these, the following theories are most credible: (1) the switch from nasal to oronasal breathing (due to nasal obstruction) causes loss of nasal airflow resulting in decreased nasal receptor-derived stimulation of ventilation and changes in phasic activity leading to decreased upper airway patency; and (2) the increased nasal airway resistance (due to nasal obstruction) generates an increased negative inspiratory force/pressure causing turbulence in the relaxed soft tissues and upper airway collapse (retropharyngeal) resulting in upper airway obstruction and SDB.
These hypotheses are based on a few studies that have used varying methods and small numbers of study subjects and therefore require further confirmation. If this is found to be true, technologies and treatments aimed at facilitation of nasal breathing should be explored further in the context of SDB. In the interim, use of topical nasal steroids in patients with SDB and preferential use of nasal CPAP in treatment may be reasonable.
Longitudinal studies in children with nasal obstruction are required to determine the risk factors for SDB, including the relationship of nasal obstruction to structural abnormalities of the face and upper airway. It is possible that certain congenital variations in facial structures are deleterious to nasal breathing and exacerbated by nasal obstruction from other causes. Knowledge of these factors could be useful in preventing the development of SDB.
The effect of CPAP on the nasal airway is relatively unexplored. Anecdotally, it appears that CPAP may increase nasal inflammation and, in some, promote vasomotor rhinitis. It is possible this may lead to decreased adherence to treatment. This is another area in need of further research.