SPO 2 control with adaptive linear compensation

• US 8,528,552 B2
• Filed: 11/30/2009
• Issued: 09/10/2013
• Est. Priority Date: 12/01/2008
• Status: Active Grant

• Current Assignee: Dragerwerk AG & Company KGaA (FPS Vermögensverwaltung GmbH)
• Original Assignee: Drager Medical GmbH (FPS Vermögensverwaltung GmbH)
• Inventors: von Blumenthal, Tilman
• Primary Examiner(s): Yu, Justine
• Assistant Examiner(s): TSAI, MICHAEL JASPER
• Application Number:
  US12/627,428
• Publication Number:
  US 20100139659A1
• Time in Patent Office: 1,380 Days
• Field of Search: 128/200.24, 128/203.12, 128/203.14, 128/203.25, 128/204.18, 128/204.21, 128/204.22, 128/204.23, 128/204.26, 128/205.11
• US Class Current: 128/204.21
• 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 16/0833 T- or Y-type connectors, e.g. Y-piece
• CPC Class Codes: A61M 16/12 by mixing different gases
• CPC Class Codes: A61M 16/16 Devices to humidify the respiration air A61M16/1045 takes precedence
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)

Abstract

A device and a process for controlling a respirator with inclusion of an oxygen saturation value (34) for compensating a device-dependent time response (15), a physiological time response (16) and a measuring method-dependent time response (17) are described. The device-dependent time response (15), the physiological time response (16) and the measuring method-dependent time response (17) are determined in a continuous sequence and a run time of a change in the oxygen concentration from the metering means (9) in the respirator to the patient (4) is determined and taken into account in regulating the oxygen concentration.

Claims

1. A process for controlling a respirator, the respirator comprising a control and calculating unit, a gas path, a gas-mixing unit, a gas-metering unit, a measuring arrangement for measuring an oxygen saturation, an input unit and a controller, the process comprising the steps of:

providing a humidifying unit;

providing at least one time function element;

simulating one or more time responses of the respirator and said humidifying unit, the measuring arrangement for measuring an oxygen saturation and a patient in said at least one time function element;

providing a set value of an oxygen concentration in the respirator, wherein a run time of a change in the oxygen concentration through at least said humidifying unit is determined based on at least said set value of said oxygen concentration and said one or more time responses of said respirator and said humidifying unit;

determining a saturation-effective oxygen concentration based on at least said run time of said change in said oxygen concentration;

determining a measured value of a current oxygen saturation;

providing a set point of an oxygen saturation to the respirator;

determining a difference value of an oxygen concentration from said set point of the oxygen saturation and said measured value of the current oxygen saturation; and

linking said difference value of the oxygen concentration with said saturation-effective oxygen concentration to form an updated set value of the oxygen concentration and setting a metering of said oxygen concentration in the respirator based on said updated set value of the oxygen concentration, wherein said updated set value of the oxygen concentration is provided as input to said at least one time function element.

2. A process in accordance with claim 1, wherein the set value of the oxygen concentration is complemented by a measured value of the oxygen concentration.

3. A process in accordance with claim 1, wherein the time curve of the set value is compared with a time curve of the measured value of the oxygen saturation and the modeling of said one or more time responses is changed based the time curve comparison.

4. A process in accordance with claim 1, wherein a frequency response of the set value of the oxygen concentration is compared with a frequency response of the measured value of the oxygen saturation and modeling of said one or more time responses is changed based on the frequency response comparison.

5. A process in accordance with claim 1, wherein a quality index of the measured oxygen saturation values is sent to the control and calculating unit and the measured value of the oxygen saturation is changed based on the quality index of the set of measured values.

6. A process for controlling a respirator, said respirator comprising a control and calculating unit, a gas path, a gas-mixing unit, a gas-metering unit, a measuring arrangement for measuring an oxygen saturation, an input unit, a controller and a humidifying unit, the process comprising the steps of:

providing at least one time function element;

simulating at least one time response of at least the respirator and the humidifying unit in said at least one time function element;

providing a set value of an oxygen concentration to the respirator;

determining a saturation-effective oxygen concentration based on said set value of the oxygen concentration in the respirator and a curve of the set value and said at least one time function element;

determining a measured value of a current oxygen saturation;

providing a set point of an oxygen saturation to the respirator;

determining a difference value of the oxygen concentration based on said set point of the oxygen saturation and said measured value of said current oxygen saturation;

linking the difference value of the oxygen concentration and the saturation-effective oxygen concentration to a new set value of the oxygen concentration and setting a metering of the oxygen concentration of the respirator based on said new set value of the oxygen concentration;

adjusting said at least one time response of at least the respirator and the humidifying unit based on said new set value of the oxygen concentration.

7. A process for controlling a respirator with an expiration valve, a control and calculating unit, a gas path, a gas-mixing unit, a gas-metering unit with a set value of the oxygen concentration, a measuring arrangement for measuring an oxygen saturation, an input unit, a humidifying unit and a controller, the process comprising the steps of:

a) determining a device-dependent time response of the respirator, said humidifying unit and the gas path in a first step and simulating said device-dependent time response in at least one time lag element, said gas path comprising a feed line connected to said humidifying unit and a Y-piece;

b) determining a run time of a change in the oxygen concentration from a metering means in the respirator through said humidifying unit to said Y-piece based on a set value of the oxygen concentration and a curve of the set value of the oxygen concentration and said at least one time lag element and calculating a patient-side oxygen concentration based on said run time of said change in said oxygen concentration;

c) performing an oxygen saturation measurement in a third step with the measuring arrangement and determining a set of measured oxygen saturation values;

d) determining a first time response and a second time response in a fourth step and simulating said first time response and said second time response in at least one other time lag element, said first time response corresponding to a time response of oxygen being transported from inspired air into a blood circulation, said second time response being dependent on a measuring method, said second time response being based on the measuring arrangement used to measure the oxygen saturation;

e) determining a saturation-effective oxygen concentration in a fifth step from the patient-side oxygen concentration and the at least one lag element and at least one other time lag element;

f) forming a difference value in a sixth step based on the set of measured oxygen saturation values and a set point of the oxygen saturation;

g) generating a breathing gas oxygen concentration via a controller based on the difference value in a seventh step; and

h) linking the breathing gas oxygen concentration in an eighth step with the saturation-effective oxygen concentration to a corrected set value of the oxygen concentration, said corrected set value of the oxygen concentration being transmitted to a gas-metering unit and at least said one other time lag element, the gas-metering unit correcting the oxygen concentration based on said corrected set value, said at least one other time lag element determining said first response time and said second response time based on at least said corrected set value of the oxygen concentration.

8. A process in accordance with claim 7, wherein said at least one other time lag element comprises a second time lag element and a third time lag element, said second time lag element simulating the time response of the oxygen transport from the inspired air into the blood circulation, said third time lag element simulating the time response of the measuring arrangement.

9. A process in accordance with claim 7, wherein the modeling of the time response of the oxygen transport from the inspired air into the blood circulation and of the measuring method-dependent time response of the measuring arrangement used to measure the oxygen saturation is combined in the fourth process step with the simulation of the device-dependent time response in a common time response.

10. A process in accordance with claim 7, wherein the process is carried out in a continuously repeating sequence of the steps b) through h) after a first-time run of the sequence from a) to h).

11. A process in accordance with claim 7, each of said time lag elements have one or more of a first-order time function element and a time function element in a series connection.

12. A process in accordance with claim 7, wherein the set of measured oxygen saturation values is taken into account in a modeling of a patient'"'"'s time response.

13. A process in accordance with claim 7, wherein a measured value of a heart rate is taken into account in a modeling of a patient'"'"'s time response.

14. A process in accordance with claim 13, wherein a quality index of the set of oxygen saturation measured values and of the measured value of the heart rate are taken into account in modeling the patient'"'"'s time response.

15. A process for controlling a respirator with an expiration valve, a control and calculating unit, a gas path, a gas-mixing unit, a gas-metering unit, a measuring arrangement for measuring an oxygen saturation, an input unit and a controller and a humidifying unit, the process comprising the steps of:

a) determining a device-dependent time response of the respirator, of the gas path and of the humidifying unit and simulating said device-dependent time response in at least one first time lag element;

b) determining a run time of a change in an oxygen concentration from a metering means in the respirator through at least said humidifying unit to the patient based on a set value and a curve of the set value of the oxygen concentration, and calculating a patient-side oxygen concentration based on said run time of said change in said oxygen concentration;

c) performing an oxygen saturation measurement with the measuring arrangement and determining a set of measured oxygen saturation values;

d) determining an oxygen transport time response and a measuring method-dependent time response and simulating said oxygen transport time response and said measuring method-dependent time response in at least one other time lag element, said oxygen transport time response corresponding to oxygen being transported from inspired air into a blood circulation over time, said measuring method-dependent time response being dependent upon the measuring arrangement used to measure the oxygen saturation;

e) determining a saturation-effective oxygen concentration from the patient-side oxygen concentration and said at least one time lag element and said at least one other time lag element;

f) forming a difference value from the set of measured oxygen saturation values and a set point of the oxygen saturation;

g) generating a breathing gas oxygen concentration with a controller from the difference value; and

h) linking the breathing gas oxygen concentration with the saturation-effective oxygen concentration to a corrected set value of the oxygen concentration, said corrected set value of the oxygen concentration being transmitted to a gas-metering unit and said at least one other time lag element, the gas-metering unit correcting the oxygen concentration based on said corrected set value, said at least one other time lag element determining said oxygen transport time response and said measuring method-dependent time response based on at least said corrected set value;

continuously repeating sequence of the steps a) through h).

16. A process for controlling a respirator, the process comprising the steps of:

providing a respirator comprising an expiration valve, a control and calculating unit, an input unit, a controller, a humidifying unit, a gas path comprising one or more feed lines and a Y-piece, a gas-mixing unit and a gas-metering unit, said Y-piece being connected to said humidifying unit and said one or more feed lines, said respirator comprising a control loop for setting an oxygen saturation corresponding to a preset set value at a patient, wherein the control loop comprises a measuring component, said measuring component comprising a measuring arrangement for measuring an oxygen saturation, said control loop comprising a modeling element, wherein said modeling element comprises a first time lag element with a device-dependent time response of said respirator and said humidifying unit;

calculating an oxygen concentration value at the Y-piece and a saturation-effective oxygen concentration based on said device-dependent time response, wherein a change in a run time in an oxygen concentration through said one or more feed lines and said humidifying unit to said Y-piece is determined based on a set value of oxygen concentration and said device-dependent time response;

additively linking said saturation-effective oxygen concentration with an output of said controller via a feedback and sending a summation signal as output to the gas-metering unit and to the modeling element, said summation signal comprising a new set value of oxygen concentration, wherein said new set value of oxygen concentration is provided to said modeling element as input.

17. A process in accordance with claim 16, further comprising the step of:

respirating at least one premature or newborn child with the respirator such that damage to the eyes of the premature or newborn child and total or partial blindness of the premature or newborn child are prevented.

18. A process in accordance with claim 16, further comprising the step of:

respirating children, youth and adults with the respirator such that hypoxic states of patients are prevented.

19. A process for controlling a respirator, the process comprising the steps of:

providing a respirator, said respirator comprising a humidifying unit, an expiration valve, a control and calculating unit, a controller, an input unit, a gas path with at least one feed line and a Y-piece, a gas-mixing unit and a gas-metering unit, said humidifying unit being connected to said Y-piece and said at least one feed line, said control and calculating unit comprising a control loop for setting an oxygen saturation corresponding to a preset set value at a patient, wherein said control loop comprises a measuring component, said measuring component comprising an oxygen saturation sensor and an oxygen saturation-measuring unit, said control loop comprising a modeling element, wherein said modeling element comprises a first time lag element with a device-dependent time response, a second time lag element with a patient-dependent time response and a third time lag element with a time response dependent on the measuring method, said device-dependent time response comprising a device-dependent time response of at least said humidifying unit;

calculating an oxygen concentration value at the Y-piece and a saturation-effective oxygen concentration based on said device-dependent time response, said patient-dependent time response and said measuring method-dependent time response, wherein a run time of a change in an oxygen concentration through said humidifying unit and said at least one feed line to said Y-piece is determined based on at least said device-dependent time response;

linking the saturation-effective oxygen concentration with an output of said controller via a feedback and sending a summation signal to the gas-metering unit and to the modeling element, said summation signal comprising a corrected oxygen concentration value, said modeling element receiving said corrected oxygen concentration value and said modeling element determining one or more of said device-dependent time response, said patient-dependent time response and said time response dependent on the measuring method based on at least said corrected oxygen concentration value.

20. A process in accordance claim 19, wherein said device-dependent time response comprising a time response of said humidifying unit.

21. A process in accordance with claim 19, further comprising the step of:

respirating patients in an adverse medical care situation with the respirator.

22. A device for controlling a respirator comprising an expiration valve, a control and calculating unit, an input unit, a humidifying unit, a gas path with a Y-piece connected to the humidifying unit, a gas-mixing unit, a gas-metering unit, the device comprising:

a control loop for setting an oxygen saturation corresponding to a preset set value at a patient, wherein said control loop comprises a measuring component, said measuring component comprising a measuring arrangement for measuring an oxygen saturation, said control loop comprising a modeling element, wherein said modeling element comprises a first time lag element with a device-dependent time response of at least said humidifying unit, said control loop comprising a controller, said controller providing a controller output signal as output, wherein said modeling element is connected to said controller output signal via a feedback, said device-dependent time response and said controller output signal forming a summation signal, said summation signal being sent to the modeling element as an input variable and to the gas-metering unit as a set value of the oxygen concentration, said gas-metering unit setting an oxygen concentration in the breathing gas of patient based on said set value, said gas-metering unit determining a change in the oxygen concentration through at least said humidifying unit based on at least said device-dependent time response.

23. A device in accordance with claim 22, wherein said humidifying unit is contained in said gas path from the respirator to the patient and said modeling element includes the humidifying unit in the first time lag element with the device-dependent time response.

24. A device for controlling a respirator, the respirator comprising an expiration valve, a control and calculating unit, an input unit, a humidifying unit, a gas path with at least one feed line and a Y-piece connected to the humidifying unit, a gas-mixing unit and a gas-metering unit, the device comprising:

a control loop for setting an oxygen saturation corresponding to a preset set value at a patient, wherein said control loop comprises a measuring component, said measuring component comprising an oxygen saturation sensor and an oxygen saturation-measuring unit, said control loop comprising a modeling element and a controller, said controller providing a controller output signal as output, wherein said modeling element comprises a first time lag element with a device-dependent time response of at least said humidifying unit, a second time lag element with a patient-dependent time response and a third time lag element with a time response dependent upon a measuring method, said modeling element being connected to said controller output signal via a feedback, wherein output from said modeling element and said controller output signal form a summation signal, said summation signal being sent as an input variable to the modeling element and to the gas-metering unit as a set value of an oxygen concentration, said gas-metering unit setting an oxygen concentration in the breathing gas of patient based on said set value, said modeling element adjusting at least said device-dependent time response of said humidifying unit, said patient-dependent time response and said time response dependent upon a measuring method based on said summation signal.

25. A device in accordance with one of the claim 24, wherein each of said time lag elements have a first-order time function element and a dead time function element in a series connection.

26. A device in accordance with claim 24, wherein a set of measured oxygen saturation values is sent to the second time lag element.

27. A device in accordance with claim 26, wherein a measured value of a heart rate is sent to the second time lag element.

28. A device in accordance with one of the claim 27, wherein a quality index of the set of measured oxygen saturation values and of the measured value of the heart rate is sent to the second time lag element.

29. A device in accordance with claim 26, wherein a quality index of the set of measured oxygen saturation values is sent to the control and calculating unit and the measured value of the oxygen saturation is changed corresponding to the quality index of the set of measured values.

30. A device in accordance with claim 24, wherein said humidifying unit is arranged during inspiration in the gas path leading to the patient, wherein the humidifying unit is taken into account in the modeling element in the first time lag element.