SE Martin, I Marshall and NJ Douglas
Department of Medicine, University of Edinburgh, Scotland.

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.

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