Medical Device For Assessing Intravascular Blood Volume And Technique For Using The Same

• US 20100249559A1
• Filed: 03/25/2009
• Published: 09/30/2010
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Lovejoy, David
• Granted Patent: US 8,221,319 B2
• Time in Patent Office: Days
• US Class Current: 600/364
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)

Abstract

Embodiments of the present invention relate to a system and method for determining a physiologic parameter of a patient. Specifically, embodiments of the present invention include methods and systems for correcting a pulse oximetry plethysmographic waveform variability measurement based on parameters that may influence the waveform variability. The corrected measurement may be used to estimate intravascular blood volume and/or fluid responsiveness of a patient.

Claims

1. A method, comprising:

using a processor;

receiving a plethysmographic waveform signal from a sensor, wherein the plethysmographic waveform signal is generally representative of a blood oxygen saturation of a patient;

receiving information related to a patient parameter that may influence the plethysmographic waveform signal; and

determining plethysmographic waveform variability based at least in part on the plethysmographic waveform signal and/or the information related to the patient parameter.

2. The method of claim 1, comprising providing an indication of intravascular blood volume based on the plethysmographic waveform variability.

3. The method of claim 1, comprising triggering an alarm when the plethysmographic waveform variability is greater than a predetermined level or outside of a predetermined range.

4. The method of claim 3, wherein the predetermined level is about 15%.

5. The method of claim 1, wherein the information related to the patient parameter comprises a tissue carbon dioxide level, a tissue water fraction, and/or a combination thereof.

6. The method of claim 1, wherein the information related to the patient parameter comprises a ventilator setting of positive end pressure ventilation, a tidal volume, a respiration rate, an end-tidal carbon dioxide level, and/or any combination thereof.

7. The method of claim 1, wherein the information related to the patient parameter comprises a clinical condition of the patient and/or information related to a pharmacological treatment.

8. The method of claim 7, wherein the clinical condition comprises a likelihood of vasoconstriction.

9. A monitor, comprising:

an input circuit capable of receiving a plethysmographic waveform signal and information relating to a patient parameter that influences the plethysmographic waveform signal;

a memory storing an algorithm configured to calculate a plethysmograhpic waveform variability based at least in part on the plethysmographic waveform signal and/or the information related to the patient parameter; and

an output circuit configured to provide an indication of the plethysmograhpic waveform variability.

10. The monitor of claim 9, wherein the information relating to a patient parameter comprises information received from a carbon dioxide sensor and/or a tissue water fraction sensor.

11. The monitor of claim 9, wherein the information relating to a patient parameter comprises respiratory parameter information.

12. The monitor of claim 9, wherein the algorithm comprises the following equation:

W_v=(W_max−

W_min)/W_mean,

wherein W_v is the plethysmograhpic waveform variability, W_max is a maximum peak value for a largest peak, W_min is a minimum peak value for a smallest peak, and W_mean represents the mean vertical distance between peak maxima and minima for the consecutive peaks in the window within a window of consecutive peaks.

13. The monitor of claim 9, wherein the information related to the patient parameter comprises a tidal volume, and wherein the algorithm is configured to adjust the plethysmographic waveform variability when the tidal volume is outside of a range of between about 8 to about 15 kg/ml.

14. The monitor of claim 9, wherein the information relating to the patient parameter comprises information that the patient is undergoing positive end expiratory pressure ventilation, and wherein the algorithm is configured to increase the plethysmographic waveform variability based on the information.

15. The monitor of claim 9, wherein the information relating to the patient parameter comprises information that the patient is receiving vasoconstrictive drugs, and wherein the algorithm is configured to adjust the plethysmographic waveform variability based on the information.

16. A system for automatically controlling delivery of a fluid, comprising:

a delivery mechanism capable of delivering a fluid to a patient; and

a controller, wherein the controller is capable of;

receiving a plethysmograhpic waveform signal and information relating to a patient parameter that influences the plethysmographic waveform signal;

determining a plethysmograhpic waveform variability based at least in part on the plethysmographic waveform signal and the information related to the patient parameter; and

generally automatically adjusting delivery of the fluid based on a comparison of the plethysmograhpic waveform variability with a predetermined value.

17. The system of claim 16, comprising a ventilator capable of delivering a gas mixture to the patient, wherein the information related to the patient parameter comprises a setting or parameter of the ventilator.

18. The system of claim 16, wherein the delivery mechanism is capable of delivering the fluid comprises an intravenous fluid pump.

19. The system of claim 16, comprising a sensor capable of providing the information related to the patient parameter physiologic parameter.

20. The system of claim 19, wherein the sensor comprises a carbon dioxide sensor and/or a tissue water fraction sensor.