Comparison of INVOS 5100C and Nonin SenSmart X-100 oximeter performance in preterm infants with spontaneous apnea

Background Tissue oximeters are not interchangeable. Two instruments with sensors dedicated to preterm infants-INVOS 5100C and Nonin SenSmart X-100-have not yet been compared. Methods By measuring cerebral oxygenation in ten preterm infants with spontaneous apneic episodes defined by pulse oximeter readings (SpO(2)) below 80%, as well as tissue oxygenation during vascular occlusion on the forearm of ten adults, simultaneously we compared performance in the hypoxic range. Results We found the mean conversion equations to be StO(2,SenSmart X-100) = 0.34 x StO(2,INVOS 5100C) + 44.8% during apnea in infants and StO(2,SenSmart X-100) = 0.59 x StO(2,INVOS 5100C) + 34.4% during vascular occlusion. The individual regressions displayed large and statistically significant variations in both infants and adults. In three infants the INVOS sensor showed very little reaction to decreases in SpO(2). Conclusions These findings confirm that different NIRS devices give very different estimates when the oxygenation is low. The large variation when compared to SpO(2) suggest that the sensor placement is very important in preterm infants.