Ventilatory assistance using an external effort sensor

• US 20040221847A1
• Filed: 06/16/2004
• Published: 11/11/2004
• Est. Priority Date: 09/15/1999
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Gordon Joseph Malouf, Michael Berthon-Jones
• Inventors: Berthon-Jones, Michael, Malouf, Gordon Joseph
• Granted Patent: US 7,100,609 B2
• Time in Patent Office: Days
• US Class Current: 128/204.18
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• 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 2016/0024 with an on-off output signal, e.g. from a switch
• CPC Class Codes: A61M 2230/60 Muscle strain, i.e. measured on the user
• CPC Class Codes: A61M 2230/63 Motion, e.g. physical activity

Abstract

The ventilator of the invention uses a respiratory effort sensor that does not rely on respiratory airflow or pressure for synchronization, such as a device that measures movement of the suprasternal notch in response to respiratory efforts. This makes the ventilator relatively immune to leaks. Furthermore, the mask pressure may be modulated so as to servo-control the respiratory effort signal to be zero. Because effort is servo-controlled to be near zero, it is not necessary for the effort signal to be either linear or calibrated, but merely monotonic on effort. Similarly, it is possible to achieve near 100% assistance without having to know or estimate the resistance and compliance of the patient'"'"'s respiratory system, as in those systems that provide proportional assist ventilation

Claims

1. A method for controlling a mechanical ventilator comprising the steps of:

providing a subject with breathable gas at controllable pressure;

deriving a measure of respiratory effort from the movement of the skin of the suprasternal notch; and

adjusting said controllable pressure in accordance with said measure of respiratory effort.

2. A method for controlling a mechanical ventilator in accordance with claim 1 wherein the controllable pressure is set to a higher pressure if the respiratory effort is inspiratory, and set to a lower pressure otherwise.

3. A method for controlling a mechanical ventilator in accordance with claim 1 wherein the controllable pressure is set to a higher pressure if the respiratory effort is inspiratory or if there has not been a transition from low to high pressure for a predetermined period of time since a previous pressure transition, and set to a lower pressure otherwise.

4. A method for controlling a mechanical ventilator in accordance with claim 1 wherein the controllable pressure is set to be an increasing function of the respiratory effort, inspiratory effort being taken as positive and expiratory effort being taken as negative.

5. A method for controlling a mechanical ventilator in accordance with claim 1 wherein the controllable pressure is the sum of a first pressure plus a second pressure proportional to the respiratory effort.

6. A method for controlling a mechanical ventilator in accordance with claim 1 wherein the controllable pressure is set by a servo-controller, operable to servo-control the respiratory effort to be zero.

7. A method for controlling a mechanical ventilator in accordance with claim 6 wherein the controllable pressure is made equal to a chosen positive pressure when the subject is making no respiratory effort.

8. A method for controlling a mechanical ventilator in accordance with any of claims 1-7 wherein said measure of respiratory effort is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

9. A method for controlling a mechanical ventilator comprising the steps of:

providing a subject with breathable gas at controllable pressure;

deriving a measure of respiratory effort from movement of the subject'"'"'s skin; and

adjusting said controllable pressure to be the sum of a first pressure plus a second pressure proportional to the respiratory effort.

10. A method for controlling a mechanical ventilator in accordance with claim 9 wherein said measure of respiratory effort is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

11. A method for controlling a mechanical ventilator comprising the steps of:

providing a subject with breathable gas at controllable pressure;

deriving a measure of respiratory effort from movement of the subject'"'"'s skin; and

adjusting said controllable pressure by servo-controlling the respiratory effort to be zero.

12. A method for controlling a mechanical ventilator in accordance with claim 11 wherein said measure of respiratory effort is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

13. A method for controlling a mechanical ventilator so as to reduce the work of the heart, comprising the steps of:

providing a subject with breathable gas at controllable pressure;

deriving a measure of intrathoracic pressure from movement of the skin of the subject'"'"'s suprasternal notch; and

adjusting said controllable pressure in accordance with said skin movement.

14. A method for controlling a mechanical ventilator in accordance with claim 13 wherein said measure of intrathoracic pressure is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

15. A method for controlling a mechanical ventilator comprising the steps of:

providing a subject with breathable gas at controllable pressure;

deriving a signal that is a monotonic function of the subject'"'"'s respiratory effort and that exhibits no discontinuities; and

adjusting said controllable pressure in accordance with said derived signal.

16. A method for controlling a mechanical ventilator in accordance with claim 15 wherein the controllable pressure is adjusted to be equal to the sum of a first pressure plus a second pressure proportional to the derived signal.

17. A method for controlling a mechanical ventilator in accordance with claim 15 wherein the controllable pressure is adjusted by a servo-controller that operates to servo-control the derived signal to be zero.

18. A method for controlling a mechanical ventilator in accordance with any of claims 15-17 wherein the derived signal is approximately zero for zero inspiratory effort.

19. A method for controlling a mechanical ventilator in accordance with any of claims 15-17 wherein the derived signal is other than a function of measurement on the air breathed by the subject.

20. A method for controlling a mechanical ventilator in accordance with any of claims 15-17 wherein the derived signal is approximately zero for zero inspiratory effort, and the derived signal is other than a function of measurement on the air breathed by the subject.

21. A mechanical ventilator comprising:

a source of breathable gas at a controllable pressure;

a transducer for measuring respiratory effort from the movement of the skin of the suprasternal notch; and

a controller that responds to said transducer and adjusts said controllable pressure in accordance with the measure of respiratory effort.

22. A mechanical ventilator in accordance with claim 21 wherein the controller adjusts the pressure to a high level if the respiratory effort is inspiratory, and adjusts the pressure to a low level otherwise.

23. A mechanical ventilator in accordance with claim 21 wherein the controller adjusts the pressure higher if the respiratory effort is inspiratory or if there has not been a transition from low to high pressure for a predetermined period of time since a previous pressure transition, and adjusts the pressure lower otherwise.

24. A mechanical ventilator in accordance with claim 21 wherein the controller adjusts the pressure to be an increasing function of the respiratory effort, inspiratory effort being taken as positive and expiratory effort being taken as negative.

25. A mechanical ventilator in accordance with claim 21 wherein the controller adjusts the pressure to equal the sum of a first pressure plus a second pressure proportional to the respiratory effort.

26. A mechanical ventilator in accordance with claim 21 wherein the controller adjusts the pressure by operating a servo-controller that servo-controls the respiratory effort to be zero.

27. A mechanical ventilator in accordance with claim 26 wherein the controller adjusts the pressure to equal a chosen positive pressure when the subject is making no respiratory effort.

28. A mechanical ventilator in accordance with any of claims 21-27 wherein the measure of respiratory effort is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

29. A mechanical ventilator comprising:

a source of breathable gas at a controllable pressure;

a transducer for measuring respiratory effort from movement of a subject'"'"'s skin; and

a controller that responds to said transducer and adjusts said controllable pressure to be the sum of a first pressure plus a second pressure proportional to the respiratory effort.

30. A mechanical ventilator in accordance with claim 29 wherein said measure of respiratory effort is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

31. A mechanical ventilator comprising:

a source of breathable gas at a controllable pressure;

a transducer for measuring respiratory effort from movement of a subject'"'"'s skin; and

a controller that responds to said transducer and adjusts said controllable pressure by servo-controlling the respiratory effort to be zero.

32. A mechanical ventilator in accordance with claim 31 wherein said measure of respiratory effort is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

33. A mechanical ventilator that reduces the work of the heart comprising:

a source of breathable gas at a controllable pressure;

a transducer for deriving a measure of intrathoracic pressure from movement of the skin of the subject'"'"'s suprasternal notch; and

a controller that responds to said derived measure and adjusts said controllable pressure in accordance with said skin movement.

34. A mechanical ventilator in accordance with claim 33 wherein said measure of intrathoracic pressure is derived by positioning a sensor that includes a light source and a photocell such that the photocell output is a function of the depth of the subject'"'"'s suprasternal notch.

35. A mechanical ventilator comprising:

a source of breathable gas at a controllable pressure;

a transducer for deriving a signal that is a monotonic function of a subject'"'"'s respiratory effort and that exhibits no discontinuities; and

a controller that adjusts said controllable pressure in accordance with said derived signal.

36. A mechanical ventilator in accordance with claim 35 wherein said controller adjusts the pressure to equal the sum of a first pressure plus a second pressure proportional to the derived signal.

37. A mechanical ventilator in accordance with claim 35 wherein said controller adjusts the pressure by servo-controlling the derived signal to be zero.

38. A mechanical ventilator in accordance with any of claims 35-37 wherein the derived signal is approximately zero for zero inspiratory effort.

39. A mechanical ventilator in accordance with any of claims 35-37 wherein the derived signal is other than a function of measurement on the air breathed by the subject.

40. A mechanical ventilator in accordance with any of claims 35-37 wherein the derived signal is approximately zero for zero inspiratory effort, and the derived signal is other than a function of measurement on the air breathed by the subject.