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 2 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°C to -30°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°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.