The Hewlett-Packard 47201A ear oximeter measures arterial O2 saturation within +/- 4% when saturation is >65%, but underestimates at lower levels and overestimates with carboxyhemoglobin.
Observational
We have shown that the Hewlett-Packard 47201A ear oximeter measures arterial O2 saturation within 95 per cent confidence limits of +/- 4 per cent when arterial blood saturation is more than 65 per cent, but at lower saturations the oximeter consistently provides a reading that is too low. The oximeter is sensitive to carboxyhemoglobin, progressively overestimating arterial saturation as carboxyhemoglobin concentration increases from 0 to 18 per cent. The time response is exponential, with a normal time constant of 3 sec, but this is halved in the fast mode or operation.
Douglas et al. (Thu,) conducted a observational in Arterial O2 saturation measurement. Hewlett-Packard 47201A ear oximeter was evaluated on Accuracy of arterial O2 saturation measurement (95% CI +/- 4%). The Hewlett-Packard 47201A ear oximeter measures arterial O2 saturation within +/- 4% when saturation is >65%, but underestimates at lower levels and overestimates with carboxyhemoglobin.