Detecting inspiratory flow limitation with temporal features of nasal airflow.

BACKGROUND: Inspiratory flow limitation is a breathing pattern during sleep caused by upper airway (UA) narrowing that occurs during snoring and various degrees of obstructive sleep apnea (OSA). Clinical examination of flow limitation relies on identifying patterns of airflow contour, however this process is subjective and lacks physiological evidence of UA narrowing. Our objective is to derive the temporal features of nasal airflow contour that characterize flow limitation. The features that correlate with UA narrowing can be used to develop machine learning classifiers to detect flow limitation with physiological support.

METHODS: Sixteen healthy adult men underwent full daytime polysomnography where the nasal airflow was recorded. Before and after sleep, we measured UA anatomical parameters including neck circumference (NC) and upper-airway cross-sectional area (UA-XSA). We extracted various temporal features of airflow and investigated their relationships with the UA anatomical parameters.

RESULTS: We found that three features were correlated with the anatomical parameters associated with UA narrowing: deviation index vs. baseline UA-XSA (r = -0.67, p = 0.01), peak amplitude variability vs. baseline UA-XSA (r = -0.69, p < 0.01), peak amplitude variability vs. ΔNC (r = 0.74, p < 0.01) and peak number vs. baseline UA-XSA (r = -0.54, p = 0.04).

CONCLUSIONS: Temporal features of airflow were associated with UA narrowing. Future studies could utilize the features to develop classifiers to detect flow limitation and assess the severity of breathing disorders during sleep in high-risk populations such as pregnant women and children.