Inclusion Criteria:

• * Diagnosed REM OSA (per baseline screening: REM AHI/nREM AHI≥2) \[31-33\]
• * REM duration\>10 minutes
• * Not using CPAP (\>1 week).

Exclusion Criteria:

• * Any uncontrolled medical condition
• * Current use of the medications under investigation
• * Use of medications expected to stimulate or depress respiration (including opioids, barbiturates, doxapram, almitrine, theophylline, 4-hydroxybutanoic acid).
• * Conditions likely to affect obstructive sleep apnea physiology: neuromuscular disease or other major neurological disorder, heart failure (also below), or any other unstable major medical condition.
• * Respiratory disorders other than sleep disordered breathing:
• chronic hypoventilation/hypoxemia (awake SaO2 \< 92% by oximetry) due to chronic obstructive pulmonary disease or other respiratory conditions.
• * Other sleep disorders: periodic limb movements (periodic limb movement arousal index \> 10/hr), narcolepsy, or parasomnias.
• * Contraindications for acetazolamide, including:
• * Hyperchloremic acidosis
• * Hypokalemia
• * Hyponatremia
• * Adrenal insufficiency
• * Impaired kidney function
• * Hypersensitivity to acetazolamide or other sulfonamides.
• * Marked liver disease or impairment of liver function, including cirrhosis.
• * Contraindications to the use of lidocaine 4%/oxymetazoline HCT.
• * Claustrophobia
• * Pregnancy or nursing