Relationship between Oral Flow Patterns,Nasal Airway,and Respiratory Events

Abstract

Objectives:

Few investigations have examined oral flow (OF) patterns during sleep. This study aimed to clarify the relationship between OF patterns, nasal airway obstruction, and obstructive respiratory events.

Methods:

Nasal flow and OF were measured separately by polysomography. OF was measured 2 cm in front of the lips using a pressure sensor. Subjects were categorized into 2 groups: those with nasal obstruction (n = 44) and those without nasal obstruction (n = 41).

Results:

OF could be divided into 3 patterns: postapneic OF, OF during flow reduction (OF during FR), and spontaneous arousal-induced OF (SpA-induced OF). Postapneic OF refers to OFs that begin at the end of obstructive respiratory events (eg, flow limitation, hypopnea, and apnea), are preceded by respiratory arousals, and are accompanied by postapneic hyperventilation. OF during FR refers to OFs that occur during respiratory event-like nasal flow reduction. SpA-induced OFs are OFs that begin during stable breathing, are preceded by spontaneous arousal but not accompanied by apnea or hypopnea. Multivariate regression analysis showed that nasal obstruction was predictive of SpA-induced OF. Only 1.3% of SpA-induced OF led to apnea or hypopnea. SpA-induced OF showed a negative correlation with the apnea-hypopnea index.

Conclusions:

Postapneic OF and OF during FR led to apnea or hypopnea and were typical patterns seen in patients with moderate and severe sleep-disordered breathing (SDB). By contrast, SpA-induced OF was not associated with apnea or hypopnea but functioned as a “nasal obstruction bypasser” seen mainly in normal subjects and patients with mild SDB.