SpO2 Infant and Pediatric Study

Inclusion Criteria: * subjects are 1-23 months (infant cohort) or 2-12 years old (pediatric cohort) * requiring arterial blood samples per the site's standard of care. Exclusion Criteria: * Fractional Methemoglobinemia (FMetHb \>2%) or Fractional carboxyhemoglobinemia (FCOHb \>3%), within 24 hours of arterial blood draw. * Severe anemia (tHb \<7g/dL) within 4 hours prior to arterial blood gas draw. * Hematocrit (Hct) \<25 within 4 hours prior to arterial blood gas draw. * Patients with injuries, deformities, or abnormalities which may prevent proper application of the sensor. * Patients on Extracorporeal Membrane Oxygenation (ECMO). * Patients receiving point of care (POC) testing for blood gases. * Patients with diseases/conditions that may cause differential (or reverse differential) cyanosis including, but not limited to: * Patent ductus arteriosus with pulmonary arterial hypertension. * Pulmonary hypertension and left-heart abnormalities aortic arch hypoplasia, interrupted aortic arch, critical coarctation, and critical aortic stenosis. * Children with transposition of the great arteries (TGA) and coarctation of the aorta or interrupted aortic arch, and TGA with suprasystemic pulmonary vascular resistance. * At the discretion of the principal investigator or designee due to the subject health condition.