Nellcor Puritan Bennett Ireland

Covidien LP

Scott McGonigle

Paul Stanley Addison

James Nicholas Watson

James Ochs

Braddon M Van Slyke

Ronald Kadlec

Rui Wang

Peter M Galen

Michael Mestek

Binwel Weng

The present invention relates to physiological signal processing, and in particular to methods and systems for processing physiological signals to predict a fluid responsiveness of a patient. A medical monitor for monitoring a patient includes an input receiving a photoplethysmograph (PPG) signal representing light absorption by a patient's tissue. The monitor also includes a perfusion status indicator indicating a perfusion status of the PPG signal, and a fluid responsiveness predictor (FRP) calculator programmed to calculate an FRP value based on a respiratory variation of the PPG signal. The FRP calculator applies a correction factor based on the perfusion status indicator.

System and method for generating an adjusted fluid responsiveness metric

Systems and methods are provided for determining respiration information from physiological signals such as PPG signals. A physiological signal is processed to generate at least one respiration information signal and an autocorrelation sequence is generated based on the at least one respiration information signal. In some embodiments, a respiration peak is identified based on the autocorrelation sequence and a composite peak is generated based on the identified peak and at least one previous respiration peak. Respiration information is calculated based on the composite peak. In some embodiments, a determination is made whether the autocorrelation sequence includes an undesired harmonic. When the autocorrelation sequence includes an undesired harmonic, the autocorrelation sequence may not be used in the calculation of respiration information.

Systems and methods for filtering autocorrelation peaks and detecting harmonics

Methods and systems are provided for determining fluid responsiveness in the presence of noise. The system may determine an instantaneous value indicative of fluid responsiveness. In some embodiments, the system may determine a difference between an instantaneous value indicative of fluid responsiveness and a previous value indicative of fluid responsiveness, and select an update characteristic based on whether the difference indicates that the fluid responsiveness is increasing or decreasing. In some embodiments, the system may determine a parameter indicative of fluid responsiveness based on the update characteristic and a previously reported value indicative of fluid responsiveness.

Methods and systems for determining fluid responsiveness in the presence of noise

Systems and methods are provided for detecting held breath events. A physiological signal, such as a photoplethysmograph (PPG) signal, is processed to extract respiration-related morphology metric signals. The morphology signals are analyzed to determine when a patient's breath is being held.

Systems and methods for detecting held breath events

A patient monitoring system may determine one or more reference points of a physiological signal. The system may select one or more fiducial points on the physiological signal relative to the reference points. The one or more fiducial points may be selected by selecting a point spaced by a time interval relative to one of the reference points. The time interval may be a predetermined constant, or the time interval may depend on physiological information. The system may generate a fiducial signal based on the selected fiducial points, calculate physiological information such as a respiration rate based on the selected fiducial points, or both.

Systems and methods for determining respiration information from a photoplethysmograph

A patient monitoring system may generate a derivative signal from a physiological signal. The derivative signal may be filtered based on a pulse rate estimate associated with the physiological signal. A plurality of crossing points may be determined for the filtered derivative signal and translated to the derivative signal. A plurality of fiducial points may be determined for the derivative signal based on the plurality of crossing points. The plurality of fiducial points may be utilized to determine physiological information from the physiological signal.

Systems and methods for determining physiological information by identifying fiducial points in a physiological signal

A patient monitoring system may receive a photoplethysmograph (PPG) signal including samples of a pulse waveform. The PPG signal may demonstrate morphology changes based on respiration. The system may calculate morphology metrics from the PPG signal, the first derivative of the PPG signal, the second derivative of the PPG signal, or any combination thereof. The morphology metrics may demonstrate amplitude modulation, baseline modulation, and frequency modulation of the PPG signal that is related to respiration. Morphology metric signals generated from the morphology metrics may be used to determine respiration information such as respiration rate.

Methods and systems are discussed for determining venous oxygen saturation by calculating a ratio of ratios from respiration-induced baseline modulations. A calculated venous ratio of ratios may be compared with a look-up table value to estimate venous oxygen saturation. A calculated venous ratio of ratios is compared with an arterial ratio of ratios to determine whether baseline modulations are the result of a subject's respiration or movement. Such a determination is also made by deriving a venous ratio of ratios using a transform technique, such as a continuous wavelet transform. Derived venous and arterial saturation values are used to non-invasively determine a cardiac output of the subject.

Venous oxygen saturation systems and methods

A patient monitoring system may receive a physiological signal such as a photoplethysmograph (PPG) signal. The PPG signal may include a pulsatile component that functions as a carrier signal and an amplitude modulation component that represents respiration information. The patient monitoring system may move the amplitude modulation component to a baseline component of the PPG signal. Respiration information may be calculated based on the amplitude modulation component.

Systems and methods for determining respiration information from a physiological signal using amplitude demodulation

A test unit may generate a pulse signal based on a pulsatile profile and a frequency modulation component of a respiratory profile. A respiration modulated signal may be generated from the pulse signal, an amplitude modulation component, and a baseline modulation component. A patient modulated signal may be generated based on the respiration modulated signal and a patient profile. The artificial PPG signal may be generated based on the patient modulated signal and an artifact profile. The artificial PPG signal may be output to an electronic device.

Systems and methods for generating an artificial photoplethysmograph signal

A signal representing physiological information may include information related to respiration. A patient monitoring system may utilize a wavelet transform to generate a scalogram from the signal. A threshold for the scalogram may be calculated, and scalogram values may be compared to the threshold. One of the scales meeting the threshold may be selected as representing respiration information such as respiration rate. The respiration information may be determined based on the selected scale.

According to embodiments, techniques for selecting a consistent part of a signal, including a photoplethysmograph (PPG) signal, are disclosed. A pulse oximetry system including a sensor or probe may be used to obtain a PPG signal from a subject. Signal peaks may be identified in the PPG signal. Characteristics of the signal peaks, including the amplitude levels of the signal peaks and/or the time-distance between the signal peaks may be used to determine if the PPG signal is consistent. In an embodiment, signal peaks are processed based on a consistency metric, and the processed signal peaks are compared to the consistency metric to determine if the PPG signal is consistent. If the PPG signal is determined to be consistent, the PPG signal may be further analyzed to determine an underlying signal parameter, including, for example, a patient respiration rate. If the PPG signal is determined to be inconsistent, the inconsistent portion of the signal may be removed from the overall signal or otherwise transformed.

Consistent signal selection by signal segment selection techniques

The present disclosure relates to monitoring a characteristic respiration rate of a patient based at least in part on a suitable time period that either precedes or follows a triggering event, such as a clinician/patient interaction, where the triggering event may negatively impact the physiological parameter. In some embodiments, physiological parameter values falling between one or more pre-set thresholds may be used to derive the characteristic physiological parameter. In some embodiments, monitoring the respiration rate may provide additional information about the patient's status. In some embodiments, confidence measures may be associated with, or may be used to analyze features of the patient signal to derive information about, the characteristic respiration rate. The patient signal used to derive a patient's respiration rate may be of an oscillatory nature or may include oscillatory features that may be analyzed to derive a characteristic respiration rate.

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Edinburgh, United Kingdom

Scott McGonigle