Oximeter reliability in a subzero environment

Background: Pulse oximeters optimize care in the pre-hospital setting. As British Columbia ambulance teams often provide care in subzero temperatures, we conducted a study to determine the reliability of 3 commercially-available portable oximeters in a subzero environment. Null Hypothesis: We hypothesized that there is no significant difference between Sao, readings obtained using a pulse oximeter at room temperature and a pulse oximeter operating at sub-zero temperatures. Methods: Subjects were stable normothermic children in intensive care on Hewlett Packard monitors (control unit) at room temperature. The test units were packed in dry ice in an insulated bin (temperature -15 degrees C to -30 degrees C) and their sensors placed on the subjects, contralateral to the control sensors. Data were collected simultaneously from test and control units immediately following validation of control unit values by co-oximetry (blood gas). Results: No data were unacceptable. Two units (Propaq 106EC and Nonin 8500N) functioned well to < -15 degrees C, providing data comparable to those obtained from the control unit (p < 0.001). The Siemens Micro O-2 did not function at the temperatures tested. Conclusions: Monitor users who require equipment to function in subzero environments (military, Coast Guard, Mountain Rescue) should ensure that function is reliable, and could test units using this method.