[Pulse oximetry as a continuous, noninvasive monitoring procedure. Comparison of 2 instruments]

Pulse oximetry allows continuous registration of the arterial oxygen saturation by using the light absorption in a wave range between 600 and 1,000 nm. In addition the peripheral pulse is determined by a plethysmographic method. Two new devices, the Biox III pulse oximeter and the Nellcor pulse oximeter were compared for the following three items: 1. The accuracy in comparison with a simultaneously determined arterial oxygen saturation. Concerning the Biox III instrument, the correlation coefficient resulted in r = 0.90, for the Nellcor device in r = 0.92. 2. The onset time for registering a suddenly appearing hypoxia: For the Biox III oximeter we found a time lag between 6 and 42 s (median 21 s), for the Nellcor Oximeter between 12-39 s (median 21 s). 3. The pulse frequency corresponded very well with the simultaneously registered heart rate of the ECG. Our results indicate that pulse oximetry--a continuous and noninvasive method--is a reliable monitor for oxygen saturation, and provides trend informations about circulation, both of which are particularly appropriate for patients breathing spontaneously.