Acetazolamide as a Means to Mitigate Falling Ventilatory Drive and Drive-dependent OSA

Inclusion Criteria:

* Ages 21-80 years
* Suspected OSA (snoring, sleepiness, witnessed apneas, other clinical symptoms) or diagnosed OSA (severity not required)
* Untreated; No use of OSA treatments within 2 weeks of the baseline study. No plans to start OSA treatments for the duration of the study protocol

Exclusion Criteria:

* Any unstable medical condition
* Current use of the study medication.
* Use of ventilatory stimulant or depressant medications that may complicated interpretation of results (including opioids, barbiturates, doxapram, almitrine, theophylline, 4-hydroxybutanoic acid).
* Contraindications for acetazolamide, including:
* Allergies to sulfonamides - e.g. acetazolamide, hydrochlorothiazide, furosemide, sulfasalazine, celecoxib, sumatriptan, and zonisamide.
* closed-angle glaucoma
* adrenal insufficiency
* known electrolyte or acid/base imbalance (hyponatremia, hypokalemia, hyperchloremia, metabolic acidosis, acidemia)
* clinically-significant kidney disorders (eGFR\<60 ml/min/1.73m2)
* clinically-significant liver disorders
* Use of more than 500 mg/day of Aspirin, due to the potential for an interaction of acetazolamide and very high doses of Aspirin (acetylsalicylic acid, a salicylate drug)
* Adrenocortical insufficiency
* Low sodium or potassium
* hyperchloremic acidosis
* Conditions likely to affect obstructive sleep apnea physiology: neuromuscular disease or other major neurological disorder, heart failure, or any other unstable major medical condition.
* Respiratory disorders other than obstructive sleep apnea:
* central sleep apnea (\>75% of respiratory events scored as central)
* chronic hypoventilation/hypoxemia (awake SaO2 \< 92% by oximetry) due to chronic obstructive pulmonary disease or other respiratory conditions
* Conditions likely to increase arousability from sleep: insomnia
* Other sleep disorders that may complicate establishment of sleep: periodic limb movements (periodic limb movement arousal index \> 10/hr), narcolepsy, or parasomnias
* For intramuscular electrodes and catheter: allergy to lidocaine
* Highly-sensitive gag reflex. Patients with a self-reported 'highly-sensitive gag reflex', including an affirmative response to 'Do you sometimes gag when brushing your teeth?', will not take part in the physiology studies given the placement of an esophageal catheter
* For intramuscular electrodes: use of aspirin or other oral anti-platelets / anti-coagulants
* For oronasal mask: severe claustrophobia
* Pregnancy or nursing