Rejection of false saturation data in optical pulse-oximeter

摘要

Pulse oximetry (PO) is a non-invasive medical device used for monitoring of the arterial oxygen saturation (SaO_2) and in particular of haemoglobin oxygenation in blood. Oxygen saturation is commonly used in any setting where the patient blood oxygen saturation is unstable, including Neonatal Intensive Care Unit (NICU). The main factor affecting PO's output data is the presence of voluntary or involuntary motion artifacts or imperfect skin-sensor contact. Various methods have been employed to reject motion artifact but have met with little success.rnThe aim of the present work is to propose a novel measurement procedure for real-time monitoring and validation of the oxygen saturation data as measured in standard pulse oxymeter. The procedure should be able to individuate and reject erroneous saturation data due to incorrect transducer-skin contact or motion artifact. In the case of short sequences of rejected SpO_2 data (time duration< 8s), we report on an algorithm able to substitute the sequence of rejected data with the "most-probable" {rescued) SpO_2 data.rnIn total we have analyzed 14 patient for a total of 310 hr, 43 min and 15 s, equivalent to a total number of samples of 1118595. For our study, we were interested to download heart rate measured with the ECG (HR_(ECG)), the heart rate as measured by the pulse oximeter (HR_(SAT)) and the SpO_2 value. In order to remove the erroneous SpO_2 values reported in the rough data in coincidence of motion artifact (top, right), we have implemented a specific algorithm which provides at the output a new sequence of SpO_2 data (validated SpO_2 data). With the aim to "rescue" SpO_2 value rejected by the previously presented algorithm, we have implemented an algorithm able to provide the "most-probable" SpO_2 values in the case of single rejected values or in the case of short sequences of invalidated data (< 8 s).rnFrom these data it is possible to observe how in the 6.8% of the observation time the SpO_2 data measured by the pulse oximeter are not validated by the use of our method (corresponding to a total time of 16 hr, 8min and 40s). The use of the proposed algorithm aiming to "rescue" data from short sequences of rejected data (< 8s) allows to increase the validated data of the 2.5%t(equivalent to 8hr, 40 min and 16s), allowing a percent of usable data of the 95.7%. Once implemented in clinic, it could be used to identify the period of the day in which the percent of rejected data increase or correlate this data to clinical procedure in order to intensify clinicians and nurses attention.