Controlled Acute Hypoxia Study Comparing Pulse Oximetry to Arterial Blood Samples During Motion

Inclusion Criteria: * Male or female of any race * 18-50 years old, inclusive * Females: negative urine pregnancy test on the day of study participation (prior to exposure to hypoxia) * Completed within the last year: physical exam by a licensed physician, physician assistant (PA), or advanced practice nurse; including a 12 lead ECG, a medical history, and blood test (complete blood count and sickle cell trait/disease screening) * Meets specific demographic requirements for the monitoring device under study * Willing and able to provide written informed consent * Able to participate for the duration of the evaluation Exclusion Criteria: * A room-air baseline % modulation \< 1.5% on all four fingers on the test hand * Under 18 years or over 50 years of age * Pregnant and/or lactating women * Hypertension: on three consecutive readings, systolic pressure greater than 145 mm Hg or diastolic pressure greater than 90 mm Hg * Ventricular premature complexes (VPC's) that are symptomatic or occur at a rate of more than four per minute * History of seizures (except childhood febrile seizures) or epilepsy * History of unexplained syncope * Daily or more frequent use of anxiolytic drugs (benzodiazepines) for treatment of anxiety disorder * Recent history of frequent migraine headaches: average of two or more per month over the last year * Compromised circulation, injury, or physical malformation of fingers, toes, hands, ears or forehead/skull or other sensor sites which would limit the ability to test sites needed for the study. (Note: Certain malformations may still allow subjects to participate if the condition is noted and would not affect the particular sites utilized.) * History of acute altitude sickness at or below moderate elevation (up to 5,000-10,000 feet) defined as three or more of the following symptoms: moderate to severe headache, general malaise, dizziness/lightheadedness, nausea/vomiting, fatigue/weakness, shortness of breath, nosebleed, persistent rapid pulse, or peripheral edema * History of significant respiratory disease such as severe asthma or emphysema or sleep apnea * Sickle cell disease or trait * Clinically significant abnormal finding on medical history, physical examination, clinical laboratory test or ECG. Clinical significance will be assessed by the principal investigator or study physician as designated. * History of stroke, transient ischemic attack or carotid artery disease * History of myocardial ischemia, angina, myocardial infarction, congestive heart failure or cardiomyopathy * History of chronic renal impairment * Severe contact allergies to standard adhesives, latex or other materials found in pulse oximetry sensors, ECG electrodes, respiration monitor electrodes or other medical sensors * Unwillingness or inability to remove colored nail polish or artificial nails from test digit(s) * Unwillingness or inability to give informed consent * Prior or known allergies to: lidocaine (or similar pharmacological agents, e.g., Novocain) or heparin * Recent arterial cannulation (i.e., less than 30 days prior to study date) * Six or more arterial cannulations of each (right \& left) radial artery * History of clinically significant complications from previous arterial cannulation * Current use of blood thinners: prescription or daily aspirin use * History of bleeding disorders or personal history of prolonged bleeding from injury.