Ventilatory control system

• US 20070221224A1
• Filed: 03/08/2007
• Published: 09/27/2007
• Est. Priority Date: 03/20/2006
• Status: Active Grant

• Current Assignee: Philips RS North America LLC (Koninklijke Philips N.V.)
• Original Assignee: RIC INVESTMENTS LLC (Koninklijke Philips N.V.)
• Inventors: Blake, Stefanida, Pittman, Stephen, Witt, Erik
• Granted Patent: US 7,810,497 B2
• Time in Patent Office: Days
• US Class Current: 128/204.220
• CPC Class Codes: A61M 16/0045 Means for re-breathing exhaled gases, e.g. for hyperventilation treatment
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/0072 Tidal volume piston pumps
• CPC Class Codes: A61M 16/0075 Bellows-type
• 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 16/08 Bellows; Connecting tubes having means for taking samples G01N1/22; Water traps; Patient circuits
• CPC Class Codes: A61M 16/1045 Devices for humidifying or heating the inspired gas by using recovered moisture or heat from the expired gas
• CPC Class Codes: A61M 16/16 Devices to humidify the respiration air A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 16/209 Relief valves
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2016/103 the CO2 concentration
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2202/0225 Carbon oxides, e.g. Carbon dioxide
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2230/10 Electroencephalographic signals
• CPC Class Codes: A61M 2230/202 partial carbon oxide pressure, e.g. partial dioxide pressure (P-CO2)
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/43 : Composition of exhalation
• CPC Class Codes: A61M 2230/432 : partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 : partial O2 pressure (P-O2)
• CPC Class Codes: A61M 2230/60 : Muscle strain, i.e. measured on the user
• CPC Class Codes: Y10S 128/914 : Rebreathing apparatus for increasing carbon dioxide content in inhaled gas

Abstract

A system is provided for delivering a flow of breathing gas to an airway of a patient. The system includes a pressurizing flow module that generates a pressurized flow of breathing gas and a patient circuit coupled to the pressurizing flow module configured to communicate the flow of breathing gas to an airway of a patient. The system includes a sensor for monitoring a characteristic of a breathing pattern of the patient a controller that communicates with the sensor configured to increase a fraction of inspired carbon dioxide if the characteristic exceeds an upper threshold value and to provide servo-ventilation if the characteristic is less than a lower threshold value. The upper threshold value and the lower threshold value are changed based on the monitored characteristic of the breathing pattern of the patient.

Claims

1. A system for delivering a flow of breathing gas to an airway of a patient comprising:

a pressurizing flow module that generates a pressurized flow of breathing gas;

a patient circuit coupled to the pressurizing flow module configured to communicate the flow of breathing gas to an airway of a patient;

a sensor adapted to monitor a characteristic of a breathing pattern of the patient; and

a controller that communicates with the sensor and configured to increase a fraction of inspired carbon dioxide if the characteristic exceeds an upper threshold value and to provide servo-ventilation if the characteristic is less than a lower threshold value, wherein the upper threshold value and the lower threshold value are changed based on the monitored characteristic of the breathing pattern of the patient.

2. The system of claim 1, wherein the controller is configured to increase the fraction of inspired carbon dioxide in addition to providing servo-ventilation when the characteristic is less than the lower threshold value.

3. The system of claim 1, wherein the controller is configured to increase the fraction of inspired carbon dioxide by (a) effectuating rebreathing, (b) providing a supplemental source of carbon dioxide, (c) providing carbon dioxide from a reservoir adapted to capture exhaled breathing gas, (d) any combination of (a)-(c).

4. The system of claim 1, wherein the pressurizing flow module comprises a blower, a valve, or both.

5. The system of claim 1, wherein the upper threshold value and lower threshold value are the same single value.

6. The system of claim 1, wherein the characteristic is peak flow of the patient or a tidal volume of the patient.

7. The system of claim 1, wherein the controller provides servo-ventilation by supplying an increasing ratio of inspiratory pressure to expiratory pressure.

8. A system for delivering a flow of breathing gas to an airway of a patient, comprising:

a pressurizing flow module that generates a flow of breathing gas;

a patient circuit coupled to the pressurizing flow module configured to communicate the flow of breathing gas to an airway of a patient;

a sensor for monitoring a characteristic of a breathing pattern of the patient;

a carbon dioxide supplement system associated with said patient circuit; and

a controller operatively connected with said pressurizing flow module and carbon dioxide supplement system, said controller communicating with said sensor and increasing an amount of carbon dioxide in said patient circuit for inspiration by the patient if the characteristic exceeds an upper threshold value, said controller controlling said gas flow generator module to increase a ratio of inspiratory pressure to expiratory pressure provided to the airway of the patient if the characteristic is less than a lower threshold value.

9. The system of claim 8, wherein the pressurizing flow module comprises a blower, a valve, or both.

10. The system of claim 8, wherein the carbon dioxide supplement system comprises:

(a) a valve that directs expired carbon dioxide back to the patient for rebreathing;

(b) an external carbon dioxide source communicating with the patient circuit;

(c) a carbon dioxide reservoir for capturing exhaled breathing gas, or

(d) any combination of (a)-(c).

11. The system of claim 8, wherein the upper threshold value and lower threshold value are the same single value.

12. The system of claim 8, wherein the characteristic is peak flow of the patient, or a tidal volume of the patient.

13. The system of claim 8, wherein the system provides an increasing ratio of inspiratory pressure to expiratory pressure with a decreasing of the characteristic below the lower threshold value.

14. A method for determining states of ventilation of a patient undergoing respiratory therapy, comprising:

delivering a flow of gas to the airway of the patient from a source of breathing gas via a patient circuit;

monitoring a characteristic of a breathing pattern of a patient;

establishing a lower threshold value for the characteristic based on a mean value of the characteristic over a period of time; and

establishing an upper threshold value for the characteristic by increasing or decreasing an initial value for the characteristic, the upper threshold value being decreased if a change in the mean value of the characteristic exceeds a predetermined limit, and the upper threshold value being increased if a frequency of a particular therapy supplied to the patient exceeds a predetermined frequency.

15. The method of claim 14, wherein the particular therapy supplied to the patient is carbon dioxide rebreathing.

16. The method of claim 14, wherein the lower threshold value is obtained by reducing the mean value over time of the characteristic by a predetermined factor.

17. A method for treating a patient, comprising:

delivering a flow of gas to the airway of the patient from a source of breathing gas via a patient circuit;

monitoring a characteristic of the breathing pattern of the patient;

predicting a state of high respiration if a change in the characteristic over a period of time is a positive value and exceeds a predetermined limit, and predicting a state of low respiration if the change in the characteristic over a period of time is a negative value which has an absolute value that exceeds the predetermined limit; and

applying an appropriate treatment to the patient based on the predicted state.

18. The method of claim 17, wherein the characteristic is peak flow, or tidal volume.

19. The method of claim 17, wherein the period of time is dependent upon a number of breathing cycles.

20. A method of delivering pressurized breathing gas to an airway of a patient comprising:

delivering a flow of gas to the airway of the patient from a source of breathing gas via a patient circuit;

monitoring a characteristic of the breathing pattern of the patient;

determining an upper threshold value of the characteristic based on the breathing pattern of the patient;

determining a lower threshold value of the characteristic based on the breathing pattern of the patient; and

increasing the fraction of inspired carbon dioxide if the value of the characteristic exceeds the upper threshold.

21. A method for determining an ideal therapeutic window in the treatment of a patient, comprising:

applying a dose of an appropriate treatment to the patient based on a predicted or existing state of respiration;

measuring an index of instability of the patient in response to the applied dose;

recording a series of data points representing the indices of instability for each of a series of responses; and

fitting a therapeutic window that corresponds the applied dose with the index of instability below the data points for which the measured index of instability exceeds an acceptable value and above the data points for which the measured index of instability is below an acceptable value.

22. The method of claim 21, wherein the index of instability is:

(a) a ratio of the minimum and maximum peak flow,

(b) a ratio of the minimum and maximum tidal volume,

(c) a slope of a line fitted to a moving window mean or median peak flow,

(d) a slope of a line fitted to a moving window mean or median tidal volume, or

(e) a measure or predictor of loop gain of the patient'"'"'s respiratory control system.

23. A method for treating a patient within an ideal therapeutic window, comprising:

applying a dose of an appropriate treatment to the patient based on a predicted or existing state of respiration;

measuring an index of instability of the patient in response to the applied dose;

recording a series of data points representing the indices of instability for each of a series of responses;

fitting a therapeutic window that corresponds the applied dose with the index of instability below the data points for which the measured index of instability exceeds an acceptable value and above the data points for which the measured index of instability is below an acceptable value; and

applying subsequent doses of treatment within the therapeutic window.

24. The method of claim 23, wherein the index of instability is:

(a) a ratio of the minimum and maximum peak flow,

(b) a ratio of the minimum and maximum tidal volume,

(c) a slope of a line fitted to a moving window mean or median peak flow,

(d) a slope of a line fitted to a moving window mean or median tidal volume, or

(e) a measure or predictor of loop gain of the patient'"'"'s respiratory control system.