Method For Ventilation

• US 20110041850A1
• Filed: 07/28/2010
• Published: 02/24/2011
• Est. Priority Date: 08/20/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Vandine, Joseph Douglas, Sanborn, Warren G., Hyde, David
• Granted Patent: US 8,789,529 B2
• Time in Patent Office: Days
• US Class Current: 128/204.23
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61M 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• CPC Class Codes: A61M 16/0051 with alarm devices
• 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 16/12 by mixing different gases
• CPC Class Codes: A61M 2016/0018 electrical
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/003 with a flowmeter
• CPC Class Codes: A61M 2016/0033 electrical
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2202/0266 Nitrogen (N)
• CPC Class Codes: A61M 2230/06 Heartbeat rate only
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/42 Rate
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)

Abstract

The disclosure describes a method for automatically initiating ventilation, controlling ventilation, transitioning a ventilator to subject controlled ventilation, and weaning a subject from ventilation. The disclosure describes that the method for automatically initiating ventilation includes inputting a physical characteristic of the subject into a ventilator. The physical characteristic may be ideal body weight, height, or age. Based on the inputted physical characteristic, one or more ventilation parameters are calculated. The disclosure describes initiating ventilation based on the calculated parameters. During ventilation at least one physiological parameter of the subject is monitored. At least one ventilation parameter may be adjusted based on the monitoring of the physiological parameters and the inputted physical characteristic.

Claims

1. A method for automatically initiating and adjusting ventilation in a subject, comprising:

inputting a physical characteristic of the subject;

calculating one or more ventilation parameters based on the physical characteristic;

initiating ventilation based on said ventilation parameters;

monitoring at least one physiological parameter of the subject; and

adjusting at least one ventilation parameter based on the at least one physiological parameter and the inputted physical characteristic.

2. The method of claim 1, wherein said physical characteristic is selected from ideal body weight, height and age.

3. The method of claim 1, wherein said initiation of ventilation is volume assist/control ventilation wherein the step of calculating ventilation parameters comprises calculating the duration of an inspiration phase of a breath (T_INSP).

4. The method of claim 3, wherein the physical characteristic is ideal body weight and T_INSP is determined by the equation T_INSP=400+(5×

ideal body weight), where T_INSP is in milliseconds and ideal body weight is in kg.

5. The method of claim 4, wherein the step of calculating ventilation parameters further comprises calculating average inspiratory gas volume.

6. The method of claim 5, wherein V_T is determined by the equation V_T=(0.007×

ideal body weight×

60)/T_INSP.

7. The method of claim 5, further comprising calculating breath frequency wherein T_INSP:

T_EXP is a preset value.

8. The method of claim 1, wherein said initiation of ventilation is volume targeted/pressure control ventilation wherein the ventilator delivers a series of test breaths at a preset pressure.

9. The method of claim 8, wherein T_INSP is a linear function of the physical characteristic.

10. The method of claim 9 wherein each test breath is delivered at a constant pressure and T_RISE is based on a percentage of T_INSP.

11. The method of claim 10, wherein the constant pressure is about 10 to about 40 hPa and the T_RISE is about 40 to about 60 percent of T_INSP.

12. The method of claim 8, further comprising adjusting the pressure to result in a pre-defined volume target, said volume target based on the inputted physical characteristic.

13. The method of claim 12, wherein said physical characteristic is ideal body weight and the volume target is about 7 ml per kg of ideal body weight.

14. The method of claim 1, wherein the at least one physiological parameter of the subject is selected from the group comprising:

positive airway pressure (PAP), lung flow (LF), arterial oxygen saturation (S_PO₂), pulse rate, end tidal exhaled carbon dioxide concentrations (E_TCO₂), patient initiated breath rate, exhaled minute volume, and minute carbon dioxide production.

15. The method of claim 1, wherein the ventilation parameters are selected from the group comprising:

flow rate, T_INSP, F₁O₂, CPAP, PEEP, pressure, P_SENS, V_SENS, V_T, {dot over (V)}_E, T_PL, P_I, P_SUPP, E_SENS, T_A, T_H;

T_L, TC %, and PAV % support.

16. A method of automatically controlling mechanical ventilation of a subject initiating breathing efforts, comprising:

measuring positive airway pressure (PAP);

calculating the first derivative of the PAP measurement;

wherein if the first derivative approaches zero and if the pattern is repetitive, automatically adjusting at least one of T_RISE or T_INSP such that the derivative of the pressure-time waveform has no more than one inflection point.

17. A method of automatically controlling ventilation of a subject, comprising

setting an upper and lower bound for E_TCO₂;

measuring E_TCO₂ of the subject; and

if the E_TCO₂ exceeds the upper bound, automatically adjusting at least one ventilator parameter to reduce E_TCO₂.

18. The method of claim 17 wherein the ventilator parameter is breath volume (V_T) or breath frequency.

19. The method of claim 17, further comprising:

measuring maximum PAP;

wherein if maximum PAP is within a predetermined range of values, adjusting breath volume, and if E_TCO₂ exceeds upper bound, then adjusting breath frequency.

20. A method of automatically controlling mechanical ventilation of a subject, comprising

setting a S_PO₂ target value;

measuring S_PO₂;

wherein if S_PO₂ is above or below the target value, adjusting the level of oxygen in the gas mixture to achieve the S_PO₂ target value.

21. The method of claim 20, wherein the level of oxygen is adjusted based on a percentage change proportional to the desired change in S_PO₂.

22. The method of claim 20, wherein the level of oxygen is adjusted based on a desired change in F_AO₂ using an algorithm based on the computed alveolar-arterial oxygen tension difference and the oxyhemoglobin dissociation curve.

23. The method of claim 22, wherein the level of PEEP is adjusted based upon the determination of inflections point in the pressure volume plots average over two or more breaths.

24. The method of claim 20, further comprising:

utilizing an arbiter function to adjust at least one of PEEP and F₁O₂ to achieve the S_PO₂ target value.

25. The method of claim 20, further comprising:

comparing F₁O₂ with a predetermined F₁O₂ value based on a physical characteristic of the subject; and

reducing PEEP if the F₁O₂ is less than the predetermined value.

26. The method of claim 25, further comprising:

measuring S_PO₂;

comparing measured S_PO₂ with a predetermined value; and

if the measured value exceeds the predetermined value, adjusting PEEP to its preceding value.

27. A method of automatically transitioning a ventilator to subject control, comprising:

(a) determining whether the subject is attempting to initiate breaths;

(b) if the subject is not attempting to initiate breaths, periodically stimulating the subject to breath by reducing the breath rate by about 10%.

28. A method of automatically transitioning a ventilator to subject control, comprising:

(a) determining whether the subject is attempting to initiate breaths;

(b) if the subject is not attempting to initiate breaths, measuring E_TCO₂ and comparing the measured value with a pre-defined range;

(c) if the measured E_TCO₂ is within the range, reducing the breath frequency; and

(d) repeating step (a).

29. The method of claim 28, wherein if the subject is attempting to initiate breaths for at least a predetermined percentage of delivered breaths, switching the ventilator to assist mode whereby ventilator initiated breaths are suspended as long as the subject continues to initiate breaths or until the measured E_TCO₂ is below a pre-determined level.

30. The method of claim 29, wherein if measured E_TCO₂ is within the target range for a predetermined period of time, transitioning the ventilator to volume support ventilation utilizing the most recent end-inspiration pressure level as the starting point for volume support ventilation.

31. The method of claim 28, wherein said transitioning is achieved by calculating the pressure required to deliver the current breath volume and utilizing the calculated pressure as the starting pressure for volume support ventilation.

32. The method of claim 31, further comprising adjusting T_RISE to a predetermined value.

33. The method of claim 32, wherein said value is 50%.

34. The method of claim 31, further comprising adjusting T_INSP based upon flow deceleration such that the inspiration phase may be terminated once the lung flow drops to a predetermined percentage of the peak flow.

35. A method of automatically weaning a subject from a ventilator in volume support mode, comprising:

measuring at least one of E_TCO₂, V_T and breath frequency;

comparing at least one of measured E_TCO₂, V_T and breath frequency with predetermined E_TCO₂, V_T and breath frequency target ranges based on monitoring of subject parameters and an inputted IBW; and

if one or more of the measured E_TCO₂, V_T and breath frequency are within their respective target ranges for a predetermined period of time;

then transitioning the ventilator to weaning mode.

36. The method of claim 35, wherein said weaning mode comprises transitioning the ventilator from volume support ventilation to pressure support ventilation wherein the initial pressure is adjusted at a preset value below the target pressure utilized in said volume support mode.

37. The method of claim 36, further comprising reducing pressure in a step wise manner over predetermined time intervals.

38. The method of claim 37, wherein said pressure is reduced by about 2 hPa over time intervals of about 15 minutes.

39. The method of claim 37, further comprising initiating a spontaneous breath trial.

40. The method of claim 39, wherein the subject maintains at least one physiological parameter at an acceptance criteria for a defined period of time during the spontaneous breath trial.

41. The method of claim 40, further comprising providing an alert that the subject can be withdrawn from mechanical ventilation.

42. The method of claim 39, further comprising adjusting the ventilation parameters back to the volume support mode when the subject does not maintain at least one physiological parameter at an acceptable level for a defined period of time during the spontaneous breath trial.