A historical overview and update on pulse oximetry.

Pulse oximetry has revolutionized the way in which blood oxygenation is measured. It provides an accurate and relatively reliable noninvasive means for the continuous measurement of peripheral oxygen saturation in a variety of patients. The pulse oximeter has detected many clinical situations in which arterial hypoxemia (SaO 2 less than 90%) was not previously known to occur. The accuracy of this instrument depends on many factors, particularly the clinical scenario and the machine itself. The pulse oximeter is accurate under the following conditions: SaO 2 is greater than 22% in hemodynamically stable patients and greater than 35% in hemodynamically unstable patients; core body temperature is greater than 32 degrees C; cardiac index is greater than 1.5 L/min per m 2; pulse pressure is > 20 mm Hg; hematocrit is greater than 10%; hyperbilirubinemia is corrected for carboxyhemoglobin; fetal hemoglobin is at any level. Pulse oximeter readings have limited accuracy in the presence of methemoglobin, carboxyhemoglobin, nail polish, fluorescent light, and motion. This article presents a historical overview of pulse oximetry and an update on its current uses.