STUDY OBJECTIVES: To evaluate the effects of humidification on nasal symptoms and compliance in sleep apnea patients using continuous positive airway pressure (CPAP). DESIGN: A randomized, crossover design was employed. SETTING: The study was conducted at two suburban community-based hospital sleep laboratories. PATIENTS: Data were collected on 38 obstructive sleep apnea patients (mean age 44.1 years) in whom CPAP was a novel treatment. INTERVENTIONS: The interventions were heated humidity, cold passover humidity, and a washout period without humidity. MEASUREMENTS AND RESULTS: Patients were titrated with heated humidity or cold passover humidity in the laboratory and subsequently initiated on humidity. Objective compliance, self-report of factors affecting CPAP use, satisfaction with CPAP, feeling upon awakening, and daytime sleepiness were assessed at the completion of each 3-week treatment period and a 2-week washout period. Outcome measures were assessed with one-way analysis of variance followed by Scheffe post hoc comparisons. Significant main effects were observed for compliance (F2,37 = 5.2; p = 0.008), satisfaction with CPAP (F2,37 = 4.5; p = 0.01), and feeling refreshed on awakening (F2,37 = 4.4; p = 0.02). A significant decrease in daytime sleepiness was observed between baseline and each of the conditions (F3,37 = 55.5; p < 0.0001), but Epworth sleepiness scale scores did not differ between conditions (all p values > 0.56). CPAP use with heated humidity (5.52 +/- 2.1 h/night) was greater than CPAP use without humidity (4.93 +/- 2.2 h/night; p = 0.008). Compliance differences were not observed between CPAP use with cold passover humidity and CPAP use without humidity. Patients were more satisfied with CPAP when it was used with heated or cold passover humidity (p <= 0.05). However, only heated humidity resulted in feeling more refreshed on awakening (p < 0.05). No significant differences were observed among the three groups on the global adverse side effect score (F2,37 = 2.5; p = 0.09). Specific side effects such as dry mouth or throat and dry nose were reported less frequently when CPAP was used with heated humidity compared to CPAP use without humidity (p < 0.001). CONCLUSIONS: Compliance with CPAP is enhanced when heated humidification is employed. This is likely due to a reduction in side effects associated with upper airway symptoms and a more refreshed feeling upon awakening. Compliance gains may be realized sooner if patients are started with heated humidity at CPAP initiation.

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