Background: Universal access to pulse oximetry worldwide is often limited by cost and has substantial public health consequences. Low-cost pulse oximeters have become increasingly available with limited regulatory agency oversight. The accuracy of these devices often has not been validated, raising questions about performance.
Methods: The accuracy of 6 low-cost finger pulse oximeters during stable arterial oxygen saturations (SaO2) between 70% and 100% was evaluated in 22 healthy subjects. Oximeters tested were the Contec CMS50DL, Beijing Choice C20, Beijing Choice MD300C23, Starhealth SH-A3, Jumper FPD-500A, and Atlantean SB100 II. Inspired oxygen, nitrogen, and carbon dioxide partial pressures were monitored and adjusted via a partial rebreathing circuit to achieve 10 to 12 stable target SaO2 plateaus between 70% and 100% and PaCO2 values of 35 to 45 mm Hg. Comparisons of pulse oximeter readings (SpO2) with arterial SaO2 (by Radiometer ABL90 and OSM3) were used to calculate bias (SpO2 - SaO2) mean, precision (SD of the bias), and root mean square error (ARMS).
Results: Pulse oximeter readings corresponding to 536 blood samples were analyzed. Four of the 6 oximeters tested showed large errors (up to -6.30% mean bias, precision 4.30%, 7.53 ARMS) in estimating saturation when SaO2 was reduced <80%, and half of the oximeters demonstrated large errors when estimating saturations between 80% and 90%. Two of the pulse oximeters tested (Contec CMS50DL and Beijing Choice C20) demonstrated ARMS of <3% at SaO2 between 70% and 100%, thereby meeting International Organization for Standardization (ISO) criteria for accuracy.
Conclusions: Many low-cost pulse oximeters sold to consumers demonstrate highly inaccurate readings. Unexpectedly, the accuracy of some low-cost pulse oximeters tested here performed similarly to more expensive, ISO-cleared units when measuring hypoxia in healthy subjects. None of those tested here met World Federation of Societies of Anaesthesiologists standards, and the ideal testing conditions do not necessarily translate these findings to the clinical setting. Nonetheless, further development of accurate, low-cost oximeters for use in clinical practice is feasible and, if pursued, could improve access to safe care, especially in low-income countries.