Abstract
STUDY OBJECTIVES: To investigate the prevalence of mildly collapsible upper airways (defined by therapeutic continuous positive airway pressure [CPAP] values ≤ 8 cm H₂O) in moderate to severe obstructive sleep apnea patients treated with CPAP and to determine their clinical, functional, and nocturnal polysomnographic characteristics. METHODS: Eighty-seven patients with moderate to severe obstructive sleep apnea consecutively treated with CPAP were retrospectively investigated. Two nocturnal home sleep portable monitoring studies were performed at baseline and during treatment. Participants were categorized according to therapeutic CPAP values: ≤ 8 cm H₂O (group 1), 8-12 cm H₂O (group 2), ≥ 12 cm H₂O (group 3). Anthropometric, awake respiratory function, symptoms, comorbidities, and nocturnal home sleep portable monitoring studies data were collected. RESULTS: Mild upper airway collapsibility (therapeutic CPAP values ≤ 8 cm H₂O) was present in 25.3% of patients. They showed more favorable apnea-hypopnea index, oxygen desaturation index, mean nocturnal saturation, sleep time with oxygen saturation < 90%, desaturation nadir, and supine position. Oxygen desaturation index showed a weak association with anatomical collapsibility. Using the receiver operating characteristic curve, the area under the curve for the oxygen desaturation index vs CPAP pressure requirements ≤ 8 cm H₂O was low and oxygen desaturation index ≤ 40.8/h showed a sensitivity of 63.3% and a specificity of 69.2% to detect patients with mild collapsibility. CONCLUSIONS: A quarter of moderate to severe patients under CPAP therapy had mild collapsibility and were likely to also be good candidates for alternative and better tolerated non-CPAP therapies. Baseline anthropometric, clinical, and respiratory function characteristics did not predict mild upper airway collapsibility determined by CPAP pressure requirements ≤ 8 cm H₂O.