1. CPAP compliance will be significantly higher in both the heated humidity with Thermosmart™ and the nasal steroid phases compared to the double placebo phase.
2. CPAP compliance will be comparably improved in the heated humidity with Thermosmart™ phase versus the nasal steroid phase.
3. Improvement in nasal symptoms in using CPAP will be significantly improved in both the heated humidity with Thermosmart™ and the nasal steroid phases compared to the double placebo phase, and comparable between the heated humidity with Thermosmart™ phase versus the nasal steroid phase.
4. Secondary to improvements in CPAP compliance, measures of daytime functioning and quality of life will improve in the heated humidity with Thermosmart™ versus double placebo.

Eligible participants will undergo this double-blind, placebo controlled, single-blind double placebo run-in, crossover trial to determine the efficacy of heated humidity with Thermosmart™ in improving compliance and nasal symptoms in patients using CPAP versus a nasal steroid and placebo (heated humidity, nasal steroid placebo) phases. After successful screening, participants will undergo a two week single-blind double placebo run-in phase using heated humidity and a nasal steroid placebo. The double-blind treatment phase will last a total of six weeks. Participants will undergo both phases: three weeks using heated humidity with Thermosmart™ and nasal steroid placebo and three weeks using a nasal steroid with a heated humidifier. Treatment phases will be counterbalanced. Study participation will last a total of 8 weeks from screening to completion of double-blind treatment.

Inclusion Criteria:

• Between the ages of 18-65
• Diagnosis of obstructive sleep apnea (OSA) with apnea/hypopnea index (AHI) > 15/hr
• Currently using CPAP therapy and within 3 weeks to 12 months of initial CPAP titration
• Based on the CPAP nasal symptom questionnaire, a score of at least 3 (sometimes) for at least one of the following nasal symptoms related to their sleep apnea and CPAP usage: nasal congestion, runny nose, sneezing, or nasal irritation
• Willingness to tolerate and continue therapy with nCPAP
• Successfully titrated on nCPAP in a sleep center to a pressure between 6-16 cmH2O
• Willingness to comply and complete study related procedures
• Fluent in the English language

Exclusion Criteria:

• Co-morbid medical condition that is either medically significant and unstable, would interfere with the patient's ability to routinely use CPAP, or is a contraindication for use of a nasal steroid
• Women who are pregnant or who may potentially become pregnant during the course of the research trial.
• CPAP compliance over the past three weeks at screening > 5 hours/night, suggesting no compromised CPAP usage due to adverse nasal symptoms
• Wake resting SaO2 < 90%
• Currently using Bi-Level therapy, supplemental oxygen with CPAP therapy, or using a pressure outside inclusion criteria
• Currently using a Full-Face mask for CPAP therapy
• Current or prior use of the Fisher Paykel 604 CPAP machine with Thermosmart™ heated humidity.
• Patients who were never prescribed a heated humidifier with their CPAP machine (i.e. no humidifier or passover humidifier).
• Intranasal steroid treatment within the previous six months. Patient's currently taking intranasal steroid treatment cannot wash-out of steroid treatment to be included nor if patients have used nasal steroid treatment while on CPAP therapy
• Current upper airway tract infection, influenza, respiratory infection at time of screening or nasal surgery within 90 days of screening
• Prior surgical intervention for obstructive sleep apnea
• Currently taking medications that would be contraindicated to using a nasal steroid. Patients taking hypnotic or wake promoting therapy can participate if they have been on a stable dose prior to CPAP therapy and willing to maintain current dose as prescribed.
• Shift or rotating shift workers or individuals who routinely cannot contribute at least 6 hours/night to sleep/attempting therapy
• Additional sleep disorder that would interfere with routine use of CPAP