Pulse oximetry: a review of the theory, accuracy, and clinical applications

Pulse oximetry has emerged as a clinical tool in anesthesia and newborn monitoring within the last 7 years as a result of recent technological and theoretical advances. Oximeters measure the different absorption spectra of oxygenated and deoxygenated hemoglobin. Electronic measures of oxygenation at the peak of the pulse allow computation and display of oxygen saturation of the arterial blood almost instantly. Correlation coefficients between pulse oximetry and direct blood oxygen saturation measurement range from 0.77-0.99 when oxygen saturation is greater than 60%. The method is noninvasive (a clip or tape on a finger), simple to operate, and adaptable to various patient populations. Pulse oximetry monitors continuously and instantaneously, is responsive to change, and is accurate. Factors adversely affecting the accuracy of pulse oximeter output include transducer movement, peripheral vasoconstriction, a nonpulsating vascular bed, hypotension, anemia, changes in systemic vascular resistance, hypothermia, presence of intravascular dyes, and nail polish. Pulse oximetry has been used to monitor oxygen saturation intraoperatively in the adult and neonatal intensive care units and to monitor pregnant patients and their infants at delivery. Once the advantages and limitations of pulse oximetry are recognized, this monitoring technique can play an important role in the care of patients with cardiovascular and respiratory compromise.