New insights on the pathophysiology of inspiratory flow limitation during sleep.

INTRODUCTION

Inspiratory flow limitation (IFL) is defined as a "flattened shape" of inspiratory airflow contour detected by nasal cannula pressure during sleep and can indicate increased upper airway resistance especially in mild sleep-related breathing disorders (SRBD). The objective of this study was to investigate the association between upper airway abnormalities and IFL in patients with mild SRBD.

METHODS

This study was derived from a general population study consisting of selected individuals with apnea-hypopnea index (AHI) below 5 events/h of sleep, ("no obstructive sleep apnea" group) and individuals with AHI between 5 and 15 events/h ("mild obstructive sleep apnea" group). A total of 754 individuals were divided into four groups: group 1: AHI <5/h and <30 % of total sleep time (TST) with IFL (515 individuals), group 2: AHI <5/h and >30 % of TST with IFL (46 individuals), group 3: AHI: 5-15/h and <30 % of TST with IFL (168 individuals), and group 4: AHI: 5-15/h and >30 % of TST with IFL (25 individuals).

RESULTS

Individuals with complains of oral breathing demonstrated a risk 2.7-fold larger of being group 4 compared with group 3. Abnormal nasal structure increased the chances of being in group 4 3.2-fold in comparison to group 1. Individuals with voluminous lateral wall demonstrated a risk 4.2-fold larger of being group 4 compared with group 3.

CONCLUSION

More than 30 % of TST with IFL detected in sleep studies was associated with nasal and palatal anatomical abnormalities in mild SRBD patients.