| 摘要 |
An intelligent, rule-based processor (300) provides signal quality based limits to the signal strength operating region of a pulse oximeter. These limits are superimposed on the typical gain dependent signal strength limits (314). If a sensor signal appears physiologically generated, the pulse oximeter is allowed to operate with minimal signal strength, maximizing low perfusion performance. If a sensor signal is potentially due to a signal induced by a dislodged sensor, signal strength requirements are raised. Thus , signal quality limitations enhance probe off detection without significantly impacting low perfusion performance. One signal quality measure used is puls e rate density (354), which defines the percentage of time physiologically acceptable pulses are occurring. If the detected signal contains a significa nt portion of unacceptable pulses, the minimum required signal strength is rais ed proportionately. Another signal quality measure used in conjunction with pul se rate density is energy ratio (352), computed as the percentage of total ener gy contained in the pulse rate fundamental and associated harmonics. |
