The effect of posture on airway caliber with the sleep-apnea/hypopnea syndrome.
Snoring and sleep apnea are more common in the supine than seated position. We therefore studied the effect of posture on upper-airway caliber in normal subjects, snorers, and subjects with the sleep-apnea/hypopnea syndrome (SAHS). We measured upper-airway cross-sectional area by acoustic reflection in 110 SAHS patients (apnea/hypopnea index [AHI] > 15), 70 snorers without SAHS (AHI < 15), and 40 male controls matched for body-mass index (BMI) to the 40 SAHS patients. SAHS patients in the seated position had smaller upper-airway areas at the orophyngeal junction (OPJ) than either the snorers (p < 0.01) or the normal subjects (p < 0.02), but there were no differences between groups in airway cross-sectional areas in the supine or lateral recumbent positions. SAHS patients had significantly smaller decreases in OPJ area from the seated to either the supine (p < 0.001) or lateral recumbent (p < 0.001) positions than did the snorers. SAHS patients also had smaller (p < 0.05) decreases in OPJ area upon lying down than did the BMI-matched normal subjects. These data are compatible with SAHS patients defending their upper airway more upon lying down than do snorers or normal subjects.
Martin
S E
SE
Department of Medicine, University of Edinburgh, Scotland.
Marshall
I
I
Douglas
N J
NJ
D000162:Acoustics; D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D005652:Functional Residual Capacity; D005931:Glottis; D006801:Humans; D007830:Larynx / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009960:Oropharynx / Q000473:pathology*; D010614:Pharynx / Q000473:pathology*; D011187:Posture; D012115:Residual Volume; D012891:Sleep Apnea Syndromes / Q000473:pathology*; D012913:Snoring / Q000473:pathology; D016683:Supine Position; D014109:Total Lung Capacity