Study Procedures The sampling plan will include any neonate with a birth weight over 1000g, requiring an arterial line. Patients with significant pre-existing skin breakdown over the abdominal area will be excluded from the study. Recruitment will occur exclusively in the NICU. Consent will be obtained in the NICU once the arterial line has been placed. As the Principal Investigator, I, and/or other Dr. Daniel Sandler will obtain consent. We will provide the patient's parents with a summary of the protocol of the study and brochures providing information about the sensor and its manufacturer.