Reusable sensors in intrapartum foetal reflection pulse oximetry

To evaluate the accuracy of intrapartum foetal pulse oximetry (SO(2POX)) using reusable sensors and the effect of a sensor performance test on data quality. Furthermore, to assess the sensor-related costs by using reusable sensors and sensor performance test.

36 reusable sensors were used for SO(2POX) during labour of 289 term foetuses. A sensor performance test device assessing the emitter and receiver capability and the firmness of attachment of the sensors had been developed and used in the last 134 measurements before each resterilisation. Oxygen saturation (SaO(2)) at birth was measured spectrophotometrically after cord blood sampling. The accuracy of SO(2POX) was evaluated by analysing its relationship to SaO(2). The valid SO(2POX) data, as confirmed by subsequent sensor test in the second group, was considered comparable with those with single sensor use. Sensor-related average cost (sensors, test device and sterilisation) of such measurements was compared with that of single sensor use.

Eight sensors failed performance test despite valid pulse oximetry signal output during their last measurements. There were significant overall linear correlations between SO(2POX) and SaO(2) (r=0.45, P<0.0001). Separate analyses of regression in the group without sensor performance testing showed an r(2) of 0.41, whereas in the group with subsequent sensor performance testing, the r(2) was 0.52 (P<0.05). By reusing the sensors, the sensor-related cost per valid measurement was $18.9 and 71% lower compared to single use of sensors ($65).

Pulse oximetry may reflect fetal oxygen saturation. Data quality may be compromised by insufficient sensor performance, even though the reflection signal quality is acceptable. If sensor performance is tested before each measurement, reusable sensors may reduce the costs of fetal pulse oximetry.