Inclusion Criteria:
* Healthy controls: Apnea Hypopnea Index (AHI) \< 5 events/hr on in-laboratory PSG within 3 months of enrollment
* OSA group: AHI \> 10 events/hr on in-laboratory PSG within 3 months of enrollment; treated or untreated.
Exclusion Criteria:
* Sleep disordered breathing or respiratory disorders (other than OSA in the OSA group), such as central sleep apnea (\>50% of respiratory events scored as central), 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 index \> 20/hr), narcolepsy, or parasomnias.
* Any unstable major medical condition.
* Medications expected to stimulate or depress respiration (including other opioids taken at home, barbiturates, benzodiazepines, doxapram, almitrine, theophylline, 4-hydroxybutanoic acid).
* History of allergy to lidocaine or oxymetazoline.
* Contraindications for morphine, including:
* allergy to morphine or opioids
* chronic obstructive pulmonary disease, asthma, or other significant respiratory disorders
* kidney or liver dysfunction, as this can affect the metabolism and excretion of morphine, leading to increased risk of toxicity.
* women who are pregnant or breastfeeding will be excluded due to potential risks to the fetus or infant.
* history of substance abuse, particularly opioid abuse, will be excluded to prevent potential misuse or relapse.
* current use of central nervous system depressants.
* individuals with gastrointestinal obstruction. Constipation is not an exclusion criterion because morphine is only administered for one night.
* recent head injury, brain tumors, or other conditions leading to increased intracranial pressure.
* unstable heart disease, particularly those with risk factors for or a history of heart rhythm disorders.
* epilepsy or a history of seizures, as morphine can lower the seizure threshold.
* severe psychiatric conditions, particularly those with a history of psychosis, as opioids can exacerbate these conditions.
* medications that interact with morphine, such as selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), Monoamine oxidase inhibitors (MAOIs), and the atypical antidepressants buproprion and trazodone.
* untreated or unstable endocrine disorders like adrenal insufficiency or thyroid dysfunction.
