Upper airway collapsibility during sleep in upper airway resistance syndrome

Study objectives: To compare upper airway collapsibility during sleep between patients with upper airway resistance syndrome (UARS), normal subjects, and patients with obstructive sleep apnea/hypopnea syndrome (OSA/H). Design: A descriptive study of a series of clinical patients and a cohort of normal control subjects. Setting: Two academic sleep-disorders centers. Patients or participants: One hundred six adult patients with sleep-disordered breathing evaluated at the SUNY Sleep Disorders Center-Medicine and 12 adult subjects without habitual snoring or daytime sleepiness and with an apnea/hypopnea index (AHI) < 5/h evaluated at the Johns Hopkins Pediatric Sleep Disorders Center. Interventions: All subjects underwent full-night polysomnography and a determination of pharyngeal critical pressure (Pcrit). All patients had a determination of therapeutic level of nasal continuous positive airway pressure (Ptherapeutic). Measurements and results: The mean +/- SD Pcrit of the 12 normal subjects was -15.4 +/- 6.1 cm H2O; the mean Pcrit of the 22 UARS patients was -4.0 +/- 2.1 cm H2O; the mean Pcrit of the 37 patients with mild-to-moderate OSA/H (AHI >= 10/h and < 40/h) was -1.6 +/- 2.6 cm H2O; and the mean Pcrit of the 47 patients with moderate-to-severe OSA/H (AHI greater than or equal to 40/h) was 2.4 +/- 2.8 cm H2O. The Pcrit of each group differed from that of all other groups (p < 0.01). The mean Ptherapeutic of patients with UARS was 6.9 +/- 1.7 cm H2O; the mean Ptherapeutic of patients with mild-to moderate OSA/H was 7.9 +/- 1.9 cm H2O (p = 0.08 compared with the Ptherapeutic of UARS patients); and the mean Ptherapeutic of patients with moderate-to severe OSA/H was 10.5 +/- 2.4 cm H2O (p < 0.0001 compared to each of the other patient groups). Conclusion: UARS is a syndrome of increased upper airway collapsibility during sleep. The upper airway collapsibility during sleep of patients with UARS is intermediate between that of normal subjects and that of patients with mild-to moderate OSA/H.