Pathogenic aspects of snoring and obstructive apnea syndrome.

Snoring (inspiratory noise related to narrowing of the upper airways) and obstructive sleep apnea (OSA) are two aspects of the same basic disorder: sleep-related narrowing of the upper airways. Patients with OSA have been heavy snorers for years and even decades. Lying supine induces snoring and mild OSA in heavy snorers due to hypotonia of pharyngeal dilator muscles, decreasing waking neural drive and recumbent position, which contribute to functional narrowing of the upper airways. Functional factors in obstruction during sleep include (a) respiratory instability prevalent in the male sex, (b) increased extensibility of the lax tissues surrounding the oro-pharynx and (c) deficient contraction of the pharyngeal dilator muscles during inspiration. These effects are worsened by sleep deprivation and fragmentation, alcohol intake and sedatives. Anatomical factors favoring narrowing of the upper airways in snorers and OSA patients are (a) abnormally narrow airways as well as (b) increased thickness and length of the velum palatinum in snorers and OSA patients, (c) tonsillar and adenoid hypertrophy, micro- and retrognathia, and nasal insufficiency, (d) obesity with fat infiltration of the soft tissues and in particular of the oropharynx, (e) relatively open mandibular angle, hypertrophy and thickness of the tongue, and lowered hyoid bone (as shown by MRI imaging). It is possible that many anatomical abnormalities may be the consequence of snoring and obstructive apnea. During NREM sleep the ineffective inspiratory efforts progressively increase with worsening hypoxia and hypercapnia. The upper airways become patent again when arousal induces phasic activation of the dilator pharyngeal muscles.(ABSTRACT TRUNCATED AT 250 WORDS)