The effect of a disposable probe cover on pulse oximetry

The re-use of pulse oximeter probes presents the possibility of between-patient contamination. Use of a disposable polyethylene cover may reduce this risk. In a controlled, prospective study we examined the effect of such a cover on the accuracy of pulse oximetry. Each of ten volunteer subjects was monitored simultaneously by two identical Nellcor pulse oximeters, one with a plastic cover and the other, without a cover, used as a control. The pulse oximetry (SpO2) reading for each probe was recorded while subjects breathed 21% O2 and again while they breathed 10% O2. The probe cover was then swapped onto the other probe and the recordings were repeated. Ninety-five per cent limits of agreement in SpO2 (mean difference in SpO2 (1.95 x standard deviation of difference) between covered and non-covered probes were -0.6% to 0.6% while breathing 21% oxygen and -2.0% to 2.9% while breathing 10% oxygen. We conclude that a protective plastic sheath may induce a small error in pulse oximetry reading that is most marked during hypoxaemia. This error is unlikely to be of clinical significance.