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A Measure of Ventilatory Variability at Wake-Sleep Transition Predicts Sleep Apnea Severity

¹Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University Hospitals Case Medical Center ² NeuroWave Systems Inc ³Division of Clinical Epidemiology, Department of Pediatrics, Case Western Reserve University

lhibrahim{at}hotmail.com

Abstract

Rationale: Increased variability in ventilation may contribute to the pathogenesis of obstructive sleep apnea (OSA) by promoting ventilatory instability, fluctuations of neuromuscular output to the upper airway, and pharyngeal collapsibility. We assessed the association of a measure of ventilatory variability measured at the wake-sleep transition with OSA and associated covariates.

Methods: 485 participants in the Cleveland Family Study underwent overnight polysomnography with independent derivation of the Ventilatory Variability Index and the Apnea Hypopnea Index. The Ventilatory Variability Index was calculated from the variability in the power spectrum of the abdominal inductance signal over a 2-minute period beginning at sleep onset.

Results: The Ventilatory Variability Index was strongly correlated with the Apnea Hypopnea Index (r=0.43, p<0.001). After adjusting for age, body mass index, sex, and race, the Ventilatory Variability Index remained significantly associated with Apnea Hypopnea Index (p<0.001). The adjusted odds ratio for obstructive sleep apnea (Apnea Hypopnea Index 15) with each half standard deviation increase in Ventilatory Variability Index was 1.41 [1.25-1.59]. In a subgroup analysis of obese snorers, to limit analyses to those with a presumed anatomic predisposition for apnea, Ventilatory Variability Index remained associated with an elevated Apnea Hypopnea Index.

Conclusions: Increased ventilatory variability may be a useful phenotype in characterizing obstructive sleep apnea.

Key Words: Sleep apnea syndrome • sleep disordered breathing • polysomnography • apnea