Upper Airway Collapsibility During Sleep in Upper Airway Resistance Syndrome* Avram R. Gold, MD; Carole L. Marcus, MBBCh, FCCP; Francis Dipalo, DO; and Morris S. Gold, DSc 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 evalu- ated 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 H 2 O; the mean Pcrit of the 22 UARS patients was  4.0  2.1 cm H 2 O; 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 H 2 O; and the mean Pcrit of the 47 patients with moderate-to-severe OSA/H (AHI > 40/h) was 2.4  2.8 cm H 2 O. 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 H 2 O; the mean Ptherapeutic of patients with mild-to moderate OSA/H was 7.9  1.9 cm H 2 O (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 H 2 O (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. (CHEST 2002; 121:1531–1540) Key words: inspiratory flow limitation; nasal continuous positive airway pressure; obstructive sleep apnea; pharyngeal critical pressure; upper airway resistance syndrome Abbreviations: AT/ET = mean apnea time/event time; BMI = body mass index; CPAP = continuous positive airway pressure; MSLT = multiple sleep latency test; NREM = nonrapid eye movement; OSA/H = obstructive sleep apnea/ hypopnea syndrome; Pcrit = pharyngeal critical pressure; Pesoph = change in esophageal pressure; Pmask = nasal mask pressure; Ptherapeutic = therapeutic level of nasal continuous positive airway pressure; Rus = airway resistance between the nares and the point of collapse under conditions of inspiratory flow limitation; SWS = slow-wave sleep; UARS = upper airway resistance syndrome; UPPP = uvulopalatopharyngoplasty; V ˙ imax = maximal inspiratory airflow C linical investigators have recognized that inspira- tory flow limitation with arousal from sleep may be a cause of daytime fatigue and sleepiness even in the absence of obstructive sleep apnea/hypopnea syndrome (OSA/H). Patients with upper airway re- sistance syndrome (UARS) have periods of sleep associated with inspiratory flow limitation, increased inspiratory effort, and arousal. 1 Preventing inspira- tory flow limitation in patients with UARS with nasal continuous positive airway pressure (CPAP) results in a decrease in their frequency of arousals and an improvement in their daytime fatigue and sleepi- ness. 1 Therefore, understanding the pathophysiology *From the Division of Pulmonary/Critical Care Medicine (Drs. A. Gold and Dipalo), SUNY–Stony Brook, School of Medicine, DVA Medical Center, Northport, NY; Eudowood Division of Pediatric Respiratory Sciences (Dr. Marcus), Johns Hopkins Medical Institutions, Baltimore, MD; and Biostatistics and Data Management (Dr. M. Gold), Novartis Consumer Health, Summit, NJ. Supported by National Institutes of Health grants HL58585 and RR-00052. Manuscript received May 11, 2001; revision accepted November 27, 2001. Correspondence to: Avram R. Gold, MD (111D), DVA Medical Center, Northport, NY 11768 www.chestjournal.org CHEST / 121 / 5 / MAY, 2002 1531 Downloaded From: http://journal.publications.chestnet.org/ on 12/02/2015