Evidence for the need of bedside accuracy of pulse oximetry in an intensive care unit

Abstract

Objective: To compare pulse oximetry saturation (Spo2 with arterial blood gas saturation (SaO2) obtained during clinical routine to determine the optimal lowest reliable value of SpO2 in ventilator-dependent patients before setting up a nurse-directed protocol of FIO2 titration.

Design: Prospective clinical study.

Setting: Surgical intensive care unit in a university hospital.

Patients: Thirty-three patients with a pulse oximeter probe in whom arterial blood gas was measured with a radial artery line.

Interventions: SPO2 was recorded by the nurses and compared with SaO2 obtained by blood gas analysis with a co-oximeter. Two sensors currently used in our surgical intensive care unit and connected to a monitor (HP OmniCare M1165/66A; Hewett Packard, Andover, MA) were tested. In group I, the Durensor DS 100A (Nellcor Puritan Bennett, Pleasanton, CA), a reusable sensor, was used. In group II, the Oxisensor D25L (Nellcor Puritan Bennett), a nonreusable sensor, was used.

Measurements and main results: In group 1, 64 data pairs were obtained. In this group, SaO2 ranged from 87 to 98% and SpO2 ranged from 92 to 100%. The bias was -1.90% and the limits of agreement ranged from -5.56 to 1.76%. In group 11, 47 data pairs were obtained. In this group, SaO2 ranged from 87 to 99% and SpO2 ranged from 92 to 100%. The bias was -2.49% and the limits of agreement ranged from -6.62 to 1.64%.

Conclusions: In the range of SaO2 tested, regardless of the sensor used, SpO2 overestimated SaO2. Large limits of agreement were found. Based on this result, the authors concluded that before defining a nurse-directed protocol of FIO2 titration with SpO2, the material used daily must be evaluated. A minimum threshold SpO2 value of 96% in both groups I and II is more reliable to ensure SaO2 > or = 90%.