The response times during anaesthesia of pulse oximeters measuring oxygen saturations during hypoxaemic events.

Abstract

Episodes of desaturation were recorded simultaneously by computer from two Ohmeda Biox 3700 pulse oximeters, one with an ear and one with a finger probe, on patients undergoing anaesthesia. Over a period of 6 months, 28 episodes of desaturation were detected. Analysis of the recordings showed the mean minimum saturations recorded for ear and finger probes were 86.3% and 83.5% respectively (p less than 0.01). The mean delay for finger compared to ear pulse oximetry was 4.4 s (p less than 0.01). Analysis at different saturation levels showed finger probe responses to be significantly slower than ear probe responses at saturations equal to and above 91% (p less than 0.05). At saturation levels of 90% or less no significant difference in probe response times were found.