Pressure support ventilation of patients

• US 7,520,279 B2
• Filed: 07/18/2002
• Issued: 04/21/2009
• Est. Priority Date: 07/19/2001
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Berthon-Jones, Michael
• Primary Examiner(s): Yu; Justine R
• Assistant Examiner(s): Ostrup; Clinton
• Application Number:
  US10/311,920
• Publication Number:
  US 20030221689A1
• Time in Patent Office: 2,469 Days
• Field of Search: 128/200.24, 12820418-20429, 128/202.22, 128/202.27, 700/50, 700/1, 706 7- 9, 604 9301-10314, 606191-200, 600/201, 600/204, 600/207, 600/323, 600/484, 600/529, 600/533, 600/538
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2230/202 partial carbon oxide pressure, e.g. partial dioxide pressure (P-CO2)

Abstract

A methodology and apparatus for determining a target ventilation setting for delivering ventilatory support based upon a function of measured PCO₂. Patient ventilation is measured over time during a learning period in which ventilatory support is provided. A target ventilation is calculated as a function of the measured ventilation. Adjustments to the target ventilation are then made using a measure of partial pressure of CO₂ for the patient. Preferably, the measure is compared to a threshold PCO₂ and the target ventilation may be increased or decreased based upon the comparison. The target ventilation may then be increased or decreased based upon a fixed percentage of the absolute value of the difference between the measured PCO₂ and the threshold PCO₂.

Claims

1. A method for determining a target ventilation setting of a ventilator comprising the steps of:

delivering servo-controlled ventilatory support during an awake learning period to a patient;

measuring the patient'"'"'s ventilation over time during said learning period;

measuring the patient'"'"'s partial pressure of CO₂ during said learning period;

calculating a target ventilation as a function of a measure of ventilation; and

adjusting said target ventilation as a function of a measure of said partial pressure.

2. The method of claim 1 wherein said function of the measure of partial pressure comprises a function of a threshold value of partial pressure of CO₂.

3. The method of claim 2 wherein said function of a measure of partial pressure further comprises a percentage value of the measure of partial pressure.

4. The method of claim 3 wherein said percentage value is a function of said threshold value.

5. The method of claim 4 wherein said step of adjusting comprises an increase in the target ventilation if said measure of partial pressure exceeds said threshold value.

6. The method of claim 5 wherein said step of adjusting comprises a decrease in the target ventilation if said threshold value exceeds said measure of partial pressure.

7. The method of claim 6 wherein said function of the measure of partial pressure further comprises a function of the difference between the threshold value and the measure of partial pressure.

8. The method of claim 7 wherein said threshold value is about 50 mmHg.

9. The method of claim 7 wherein said percentage value is about 1%.

10. The method of claim 7 wherein said percentage value is about 0.5%.

11. An apparatus for determining a target ventilation setting of a ventilator comprising:

a supply means for providing controlled pressurized air to a patient;

a flow means for generating a flow signal representative of patient airflow;

a PCO₂ means for generating a PCO₂ signal representative of a measure of said patient'"'"'s partial pressure of CO₂;

a controller operable to (a) access data from the flow signal and the PCO₂ signal, and (b) to control the supply means, said controller with programmed instructions for executing a determination of a target ventilation setting, said instructions for delivering servo-controlled ventilatory support during a learning period to a patient;

determining a measure of said patient'"'"'s ventilation over time during said learning period; and

calculating a target ventilation as a function of the measure of the patient'"'"'s ventilation and as a function of the measure of the partial pressure of CO₂ during said learning period.

12. The apparatus of claim 11 wherein said function of the measure of partial pressure comprises a function of a threshold value of a partial pressure of CO₂.

13. The apparatus of claim 12 wherein said step of calculating comprises an increase in said target ventilation if said measure of partial pressure exceeds said threshold value.

14. The apparatus of claim 13 wherein said step of calculating comprises a decrease in said target ventilation if said threshold value exceeds said measure of partial pressure.

15. The apparatus of claim 13 wherein said PCO₂ means is a keypad and said instructions further control the step of receiving partial pressure CO₂ data entered on said keypad.

16. The apparatus of claim 12 wherein said function of the measure of partial pressure further comprises a percentage value of the measure of partial pressure.

17. The apparatus of claim 16 wherein said percentage value is a function of said threshold value.

18. The apparatus of claim 17 wherein said function of the measure of partial pressure further comprises a function of the difference between the threshold value and the measure of partial pressure.

19. The apparatus of claim 18 wherein said threshold value is about 50 mmHg.

20. The apparatus of claim 18 wherein said percentage value is about 1%.

21. The apparatus of claim 18 wherein said percentage value is about 0.5%.

22. A method for determining a target ventilation setting of a ventilator comprising the steps of:

delivering servo-controlled ventilatory support during an awake learning period to a patient;

measuring the patient'"'"'s ventilation over time during a learning period;

measuring the patient'"'"'s arterial partial pressure of CO₂ during said learning period;

calculating a target ventilation as a function of the measured ventilation; and

adjusting said target ventilation by (a) increasing the target ventilation by about 1% per mmHg over a threshold or (b) decreasing the target ventilation by about 0.5% per mmHg under said threshold as a function of the arterial partial pressure of CO₂ measured during said learning period.

23. The method of claim 22 wherein said threshold is about 50 mmHg.

24. An apparatus for determining a target ventilation setting of a ventilator comprising:

a servo-controlled blower for providing controlled pressurized air to a patient;

a transducer operable to generate a flow signal representative of patient airflow;

a blood gas monitor to generate a PCO₂ signal representative of a measure of patient partial pressure of CO₂ ;

a processor operable to (a) access data from the flow signal and the PCO₂ signal, and (b) to control the supply means, said processor with programmed instructions for executing a determination of a target ventilation setting, said instructions controlling the steps of;

delivering servo-controlled ventilatory support during a learning period to a patient;

determining a measure of patient'"'"'s ventilation over time from said learning period;

calculating a target ventilation as a function of the measure of the patient'"'"'s ventilation and as a function of the measure of the partial pressure of CO₂ taken during said learning period.

25. The apparatus of claim 24 wherein said function of the measure of partial pressure comprises a function of a threshold value of a partial pressure of CO₂.

26. The apparatus of claim 25 wherein said step of calculating comprises an increase if said measure of partial pressure exceeds said threshold value.

27. The apparatus of claim 26 wherein said step of calculating comprises a decrease if said threshold value exceeds said measure of partial pressure.

28. The apparatus of claim 25 wherein said function of the measure of partial pressure further comprises a percentage value of the measure of partial pressure.

29. The apparatus of claim 28 wherein said percentage value is a function of said threshold value.

30. The apparatus of claim 28 wherein said threshold value is about 50 mmHg.

31. The apparatus of claim 28 wherein said function of the measure of partial pressure further comprises a function of the difference between the threshold value and the measure of partial pressure.

32. The apparatus of claim 30 wherein said percentage value is about 1%.

33. The apparatus of claim 30 wherein said percentage value is about 0.5%.