Abstract
BackgroundThe ability of negative expiratory pressure (NEP) technique to differentiate between awake snorers with and without obstructive sleep apnea-hypopnea (OSAH) was investigated.MethodsForty-eight subjects with sleep disordered breathing (SDB) and 7 healthy subjects, as non-snorer controls, underwent the NEP application of -5 and -7 cmH2O in the seated and supine position during wakefulness, after performing a sleep study. The upper airway collapsibility was assessed by computing the volume exhaled during the first 0.5 sec. (V,NEP0.5) and 1 sec. (V,NEP1) following the NEP start.ResultsPatients with severe (AHI ≥ 30) (n = 19) and mild-to-moderate (AHI <30 and >5) (n = 15) OSAH had lower V,NEP0.5 (340 ± 88 ml) as compared to snorers (AHI ≤ 5) (n = 14) (427 ± 101 ml; p < 0.01) and controls (n = 7) (492 ± 69 ml; p < 0.001) in the supine position with NEP -5 cmH2O. Less significant differences among the different groups were observed for V,NEP0.5 in the seated position with NEP -5 cmH2O and in both positions with NEP -7 cmH2O (only OSAH patients vs controls, p < 0.001). Similar results were obtained for V,NEP1 in either position by using both NEP -5 cmH2O and -7 cmH2O. In spite of this, a substantial overlapping of V,NEP0.5 and V,NEP1 between snorers and OSAH patients did not allow to identify a reliable diagnostic cut-off level. An inverse correlation with AHI was found for V,NEP0.5 in the supine position with NEP -5 cmH2O (rs = -0.46, p < 0.05) in severe OSAH patients.ConclusionThe awake OSAH patients exhibit values of V,NEP0.5 and V,NEP1 lesser than those of awake snorers. The NEP technique, however, appears to have a limited usefulness as clinical tool for routine screening of the OSAH patients during wakefulness.
Highlights
Among the mechanical factors that are believed to promote obstructive sleep apnea/hypopnea (OSAH), the increase in passive upper airway compliance, as assessed by the pharyngeal volume-pressure relationship in the absence of upper airway dilator muscle activity, hasRespiratory Research 2006, 7:54 http://respiratory-research.com/content/7/1/54 been repeatedly emphasized [1,2,3,4,5,6]
There is compelling evidence that the upper airways have a smaller lumen during wakefulness [8,13,14] and sleep [3] in obstructive sleep apnea-hypopnea (OSAH) patients, who show an increase in the upper airway resistance [15,16,17,18], often assuming an anterior-posterior configuration of their major axis with a prevalent lateral narrowing [8,19]
The aim of our study was i) to investigate if volume exhaled during early application of negative expiratory pressure (NEP) at the onset of quiet expiration at rest was different in OSAH patients, snorers and normal subjects, suggesting different degrees of pharyngeal collapsibility among these groups and ii) if these differences could be used to distinguish non-apneic from apneic snorers
Summary
Among the mechanical factors that are believed to promote obstructive sleep apnea/hypopnea (OSAH), the increase in passive upper airway compliance, as assessed by the pharyngeal volume (area)-pressure relationship in the absence of upper airway dilator muscle activity, has (page number not for citation purposes)Respiratory Research 2006, 7:54 http://respiratory-research.com/content/7/1/54 been repeatedly emphasized [1,2,3,4,5,6]. There is compelling evidence that the upper airways have a smaller lumen during wakefulness [8,13,14] and sleep [3] in OSAH patients, who show an increase in the upper airway resistance [15,16,17,18], often assuming an anterior-posterior configuration of their major axis with a prevalent lateral narrowing [8,19] These factors tend to increase both the pharyngeal compliance, which is volume and shape dependent, and the closing pressure. The ability of negative expiratory pressure (NEP) technique to differentiate between awake snorers with and without obstructive sleep apnea-hypopnea (OSAH) was investigated
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