Hypoxemia is an abnormally low concentration of oxygen in the blood, and is an important sign of cardio-respiratory compromise in acutely ill patients. Pulse oximetry (PO) is a rapid, portable, non-invasive and accurate method of measuring arterial hemoglobin oxygenation (Sp02), and can therefore be readily implemented to detect hypoxemia in the clinical setting. In this research study, we propose to test the hypothesis that the use of pulse oximetry to detect hypoxemia by first-level health workers' in Karachi, Pakistan is useful and feasible for the identification of the infants most urgently in need of medical care. We will enroll 1,400 infants 0-59 days of age who present to one of two primary health centers in Karachi. Infants will undergo brief clinical assessment by a community health worker (CHW) based on the WHO/UNICEF Integrated Management of Neonatal and Child Illness (IMNCI) algorithm, assessment by two pulse oximetry devices, and examination by a physician. The primary outcomes include prevalence of hypoxemia, feasibility of PO (e.g., time to obtain measurement, number of infants for who repeat measurements are required), and concordance between paired measurements on separate devices.

Inclusion Criteria:

• Infant presenting to the Bilal or Bhains PHC in Karachi, Pakistan
• Age 0 - 59 days

Exclusion Criteria:

• Clinic visit is for scheduled injectable antibiotic administration (e.g., SAT trial)

Young infants, aged 0-59 days.