Regional saturation system with ensemble averaging

#The present disclosure relates generally to regional oximetry and, more particularly, to ensemble averaging of pulses in a detected waveform from a regional oximeter.

#This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

#In the field of medicine, medical practitioners often desire to monitor certain physiological characteristics of their patients. Accordingly, a wide variety of devices have been developed for monitoring physiological characteristics. Such devices provide doctors and other healthcare personnel with the information they need to provide healthcare for their patients. As a result, such monitoring devices have become an indispensable part of modern medicine. One technique for monitoring certain physiological characteristics of a patient is commonly referred to as regional oximetry, and the devices built based upon regional oximetry techniques are commonly referred to as regional oximeters.

#Advantages of the disclosed techniques may become apparent upon reading the following detailed description and upon reference to the drawings in which:

#FIG. 1 is a perspective view of a medical system including a medical monitor and a regional oximetry sensor, in accordance with an embodiment;

#FIG. 2 is a block diagram of components of a medical system configured to receive a trigger input, in accordance with an embodiment; and

#One or more specific embodiments of the present techniques will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

#As noted above, the signal from a regional oximetry sensor (e.g., a photo-plethysmographic (PPG) signal) may include arterial pulses and venous pulses. Arterial pulses are related to the pulsatile flow of blood ejected from the heart, and as such, occur at a frequency corresponding to the cardiac cycle (e.g., heart rate) of a patient. Arterial pulses may be used to determine the patient's pulse rate and arterial oxygen saturation and may also be used to determine whether the sensor is on the patient. Periodic variations in venous blood volume (also called venous pulses in this document) are caused by the return flow of venous blood to the heart and may be used to determine venous oxygen saturation as well as to determine if the sensor is on the patient. The venous return varies from changing intrathoracic pressure during spontaneous respiration or mechanical ventilation, and as such, the venous pulses occur at a frequency corresponding to the respiration cycle of the patient. Accordingly, it may be desirable to extract the arterial pulses and venous pulses from the PPG signal to separately determine arterial oxygen saturation and venous oxygen saturation, as well as to determine whether the sensor is on the patient. However, it may be difficult to identify the arterial and/or venous pulses in the PPG signal from artifact pulses and noise because the PPG signal may have a low signal-to-noise ratio (e.g., due to the placement of the regional oximetry sensor on the body and/or the emitter-detector spacing of the regional oximetry sensor).

#As described in detail below, the systems and methods provided herein are directed toward ensemble averaging pulses in a detected waveform from a regional oximeter based at least in part upon a trigger signal. Ensemble averaging is a temporal averaging scheme that may be utilized to combine similar signals or similar portions of the same signal in order to improve the SNR of the acquired data. In particular, ensemble averaging is used to calculate a weighted average of new samples and previous ensemble-averaged samples from one pulse-period earlier, and this weighted average may be utilized to determine a desired blood characteristic, such as arterial oxygen saturation and/or venous oxygen saturation or features extracted from the shape of an ensemble averaged arterial or venous cycle. For example, during a typical ensemble averaging operation, different weights may be assigned to different pulses, and a composite, averaged pulse waveform may be used to determine the desired blood characteristic.