Project Mountain - Comparing SpO2 and SaO2 for Accuracy

Inclusion Criteria: * Subject aged 18 years or older or parent/legal guardian of subject aged less than 18 years, willing and able to understand and provide written informed consent/assent. * Weight and/or age within intended use of at least one SpO2 sensor under test at time of enrollment. * Willing and able to wear study devices in addition to SoC devices and during SoC procedures. * In-patient within a neonatal or pediatric intensive care unit (e.g. NICU, PICU, PCICU). * Has arterial access and ability to have arterial blood samples drawn as part of their SoC and analyzed by CO-Oximetry. Exclusion Criteria: * Known pregnancy or lactating females (self-reported) * Injury, wounds, physical malformation, hyperkeratosis, or compromised/non-intact skin at sensor application site (i.e. fingers, toes, hands, feet, ears, nasal ala). Note: Certain malformations may be allowed if determined it would not affect application of sensor with the pulse oximetry system. * Self-reported severe contact allergies to standard adhesives or other materials found in pulse oximetry sensors. Note: Subject may be considered eligible if subject can wear non-adhesive sensor. * Unwillingness or inability to remove nail polish or artificial nails from sensor application site. * Nail fungus on sensor application site. * Wearing and unable to remove jewelry from sensor application site. * Dye injection within 48 hours of enrollment. * Known dysfunctional hemoglobin levels (COHb \>3%, MetHb \>2%, and ctHb \<10g/dl) * Undergoing phototherapy for neonatal hyperbilirubinemia during arterial blood sampling