Hypoxia and Heart Rate Variability

Healthy Participants Inclusion Criteria: • Ability to provide consent Exclusion Criteria: * BMI \> 40 kg/m2 * Prevalent myocardial infarction, coronary revascularization, heart failure, and stroke * Unstable medical conditions that may preclude enrollment in the protocol such as: uncontrolled angina and/or congestive heart failure, uncontrolled blood pressure or resistant hypertension, cancer, and active psychiatric disease (e.g., major depression) Nocturnal Hypoxemia Inclusion Criteria: * Ability to provide consent * Chronic respiratory condition resting Sat \< 95% off oxygen Exclusion Criteria: * BMI \> 40 kg/m2 * Prevalent myocardial infarction, coronary revascularization, heart failure, and stroke * Unstable medical conditions that may preclude enrollment in the protocol such as: uncontrolled angina and/or congestive heart failure, uncontrolled blood pressure or resistant hypertension, severe chronic obstructive pulmonary disease, cancer, and active psychiatric disease (e.g., major depression)