New Insights on the Pathophysiology of Inspiratory Flow Limitation During Sleep

IntroductionInspiratory 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.MethodsThis 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).ResultsIndividuals 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.ConclusionMore than 30 % of TST with IFL detected in sleep studies was associated with nasal and palatal anatomical abnormalities in mild SRBD patients.

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