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Topical oropharyngeal anesthesia (TOPA) increases obstructive sleep apnea (OSA) frequency in both normal subjects and loud snorers. The effects of TOPA in established OSA were assessed in six male patients with a mean age (+/- SEM) of 50 +/- 5.3 yr. Following an acclimatization night, each subject underwent two overnight sleep studies, randomly assigned to TOPA (10% lidocaine spray and 0.25% bupivocaine gargle) and control (C) (saline placebo). Patients demonstrated sleep efficiencies of 93 +/- 2.9% (mean +/- SEM) during C and 88 +/- 2.9% during TOPA. Overall apnea-hypopnea (AH) frequency, using inductance plethysmography, showed little change: 21.2 +/- 3.6 on C versus 25.1 +/- 3.5 events/h on TOPA nights (p = 0.12). There was no significant increase in AH duration with TOPA, and oxygen desaturation (> or = 4%) frequency was similar: 21.1 +/- 3.9 per hour during TOPA versus 23.6 +/- 5.9 during C. However, obstructive AHs showed a change in thoracoabdominal motion from C to TOPA nights, with an increase in events with abdominal paradox from 3.1 +/- 1.1 to 10.3 +/- 3.1 per hour (p = 0.03), and a reduction in events with ribcage paradox from 13.1 +/- 1.6 to 8.2 +/- 2.4 per hour (p = 0.08). Central and mixed AHs demonstrated similar frequencies on both nights. These data support an impairment of upper airway (UA) protective reflexes among patients with OSA.