Patient monitor for determining microcirculation state

• US 9,192,312 B2
• Filed: 01/21/2014
• Issued: 11/24/2015
• Est. Priority Date: 05/06/2010
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Al-Ali, Ammar
• Primary Examiner(s): Winakur, Eric
• Assistant Examiner(s): Fardanesh, Marjan
• Application Number:
  US14/160,316
• Publication Number:
  US 20140194711A1
• Time in Patent Office: 672 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

As placement of a physiological monitoring sensor is typically at a sensor site located at an extremity of the body, the state of microcirculation, such as whether vessels are blocked or open, can have a significant effect on the readings at the sensor site. It is therefore desirable to provide a patient monitor and/or physiological monitoring sensor capable of distinguishing the microcirculation state of blood vessels. In some embodiments, the patient monitor and/or sensor provide a warning and/or compensates a measurement based on the microcirculation state. In some embodiments, a microcirculation determination process implementable by the patient monitor and/or sensor is used to determine the state of microcirculation of the patient.

Claims

1. A patient monitor configured to determine a microcirculation state, the patient monitor comprising:

a sensor interface configured to receive a signal from a physiological sensor, the signal indicative of first and second measurement values corresponding to respective first and second physiological parameters, wherein the physiological sensor is configured to transmit light of at least one wavelength into tissue of a patient and to detect the light after it has been attenuated by the tissue, and wherein the second physiological parameter comprises a measure of perfusion; and

one or more processors configured to;

determine a relationship between the first and second physiological parameters; and

compare the determined relationship between the first and second physiological parameters with stored lookup data indicative of a microcirculation state of blood vessels to determine if a blocked or partially blocked microcirculation state exists in at least a portion of blood vessels in the tissue;

wherein the one or more processors are further configured to generate a drive signal to configure the physiological sensor to measure a light absorption characteristic of the tissue at a different wavelength in response to the determination of the microcirculation state.

2. The patient monitor of claim 1, wherein the first physiological parameter comprises oxygen saturation.

3. The patient monitor of claim 2, wherein the measure of perfusion comprises a perfusion index.

4. The patient monitor of claim 3, wherein the physiological sensor comprises a pulse oximeter sensor.

5. The patient monitor of claim 1 further comprising an alarm configured to activate when a blocked or partially blocked microcirculation state is determined to exist.

6. The patient monitor of claim 5, wherein the alarm is configured to activate when the blocked or partially blocked microcirculation state is indicative of cyanosis.

7. The patient monitor of claim 5, wherein the alarm is configured to activate when the blocked or partially blocked microcirculation state is indicative of sepsis.

8. A method of non-invasively determining a microcirculation state, the method comprising:

obtaining, at a tissue site by a non-invasive physiological sensor, first and second measurement values corresponding to respective first and second physiological parameters, the second physiological parameter comprising a measure of perfusion;

determining a relationship between the first and second physiological parameters;

comparing the determined relationship between the first and second physiological parameters with stored lookup data indicative of a microcirculation state of blood vessels to determine if a blocked or partially blocked microcirculation state exists in at least a portion of blood vessels at the tissue site; and

applying an offset to at least one of the first physiological parameter or the second physiological parameter to compensate for a blocked or partially blocked microcirculation state.

9. The method of claim 8, wherein the first physiological parameter comprises oxygen saturation.

10. The method of claim 9, wherein the measure of perfusion comprises a perfusion index.

11. The method of claim 10, wherein the non-invasive physiological sensor comprises a pulse oximeter sensor.

12. The method of claim 8, wherein determining a relationship between the first and second physiological parameters comprises generating a ratio of the first measurement value to the second measurement value.

13. The method of claim 8, wherein determining a relationship between the first and second physiological parameters corresponds to generating a trend line based on the stored data points of the first and second physiological parameters.

14. The method of claim 8, wherein the stored lookup data comprises at least one lookup curve.

15. The method of claim 8 further comprising generating an alarm signal when a blocked or partially blocked microcirculation state is determined.

16. A patient monitor configured to determine a microcirculation state, the patient monitor comprising:

a sensor interface configured to receive a signal from a physiological sensor, the physiological sensor configured to transmit light of at least one wavelength into living tissue of a patient and to detect the light after it has been attenuated by the tissue; and

one or more processors configured to determine a microcirculation state of the tissue based on at least a first physiological parameter derived from an analysis of detected attenuated light, and at least a measurement of perfusion;

wherein the one or more processors are further configured to generate a drive signal to configure the physiological sensor to measure the light absorption characteristic of the tissue monitoring site at a different wavelength in response to the determination of the microcirculation state.

17. The patient monitor of claim 16, wherein the microcirculation state comprises one of an unblocked, a blocked, or a partially blocked state.

18. The patient monitor of claim 17 further comprising an alarm configured to activate when a blocked or partially blocked microcirculation state is detected.

19. The patient monitor of claim 16, wherein the physiological sensor comprises a pulse oximeter sensor.

20. The patient monitor of claim 16 further comprising an alarm configured to activate when cyanosis is detected based at least partly on the microcirculation state of the tissue.

21. The patient monitor of claim 16 further comprising an alarm configured to activate when sepsis is detected based at least partly on the microcirculation state of the tissue.