Pulse oximetry is widely used as a noninvasive tool to estimate the patient's arterial oxygen saturation (Sao2). Used for more than four decades, it often replaces an arterial blood gas study and yields a sufficient amount of information about a person's Sao2. In addition, overnight pulse oximetry is used as an economical means to suggest sleep apnea.1 Sometimes referred to as the “fifth vital sign,” along with BP, heart rate, temperature, and respiration rate, pulse oximetry is used in a variety of health-care settings.2 Pulse oximetry is a monitoring component used during other diagnostic studies and treatments commonly performed by pulmonologists, respiratory care practitioners, and other providers in a variety of settings. Monitoring the Sao2 (or the oxygen saturation as measured by pulse oximetry, Spo2, a more recent term) of patients during pulmonary rehabilitation or respiratory therapy services, cardiopulmonary stress testing (simple and complex), high-altitude simulation testing, and ventilator management represent several examples. Pulse oximetry is also frequently used to manage patients on long-term oxygen therapy (LTOT). Although pulse oximetry is a widely accepted and a frequently used tool, the reporting and reimbursement are not well understood.