Previous studies support the presence of an upper airway reflex mechanism that contributes to the maintenance of upper airway patency during sleep. We investigated the possibility that interference with this reflex mechanism contributes to the development of obstructive sleep apnea. Eight otherwise asymptomatic snorers (seven male and one female), age 39 +/- 5.3 yr (mean +/- SEM), underwent overnight sleep studies on three successive nights. An acclimatization night was followed by two study nights randomly assigned to control (C) and oropharyngeal anesthesia (OPA). On the OPA night topical anesthesia was induced using 10% lidocaine spray and 0.25% bupivacaine gargle. A saline placebo was used on night C. All subjects slept well on both study nights (mean sleep duration was 6.2 h on both study nights), and sleep stage distribution was similar on both nights. Obstructive apneas and hypopneas (OAH) rose from 114 +/- 43 during C to 170 +/- 49 during OPA (p less than 0.02). Central apneas and hypopneas (CAH) were unchanged between the two nights (8 +/- 4.9 versus 7 +/- 3). The duration of OAH was similar on both study nights (20 +/- 1.9 s during C versus 20 +/- 1.5 s during OPA). The frequency of movement arousals terminating OAH tended to be higher during OPA (7 +/- 2.9/h) than during C (3 +/- 0.7); P = NS. The frequency of oxyhemoglobin desaturations was also higher during OPA (5 +/- 2.1/h) than during C (3 +/- 1.4), p less than 0.07.(ABSTRACT TRUNCATED AT 250 WORDS)