Supraglottic airway resistance in normal subjects and patients with occlusive sleep apnea

We assessed the flow-impeding properties of nose and pharynx combined in four normals and five patients with occlusive sleep apnea (OSA) while awake by measuring supraglottic pressure and airflow at the nose. We calculated two indices of impedance presented by the supraglottic airway: the second coefficient (K2) of Rohrer's equation and supraglottic resistance (Rsg) at 0.4 l/s. The influence of posture and nasal mucosal circulation was evaluated by measuring these indices in sitting and supine position before and after administration of a nasal decongestant. The effects of changes in posture were similar in both normals and patients: K2 and Rsg values were significantly larger in supine than in sitting position. The nasal decongestant significantly decreased both values in sitting and supine positions for normals and patients but did not eliminate the posturally induced changes. Patients had significantly greater K2 and Rsg values than normals in all conditions. These results indicate supraglottic airway narrowing in OSA patients. This narrowing probably results from structural encroachment on the pharyngeal airway.