Software for finite state machine driven positive pressure ventilator control system

• US 6,158,433 A
• Filed: 11/06/1998
• Issued: 12/12/2000
• Est. Priority Date: 11/06/1998
• Status: Expired due to Fees

• Current Assignee: Sechrist Industries, Inc. (Healogics LLC)
• Original Assignee: Sechrist Industries, Inc. (Healogics LLC)
• Inventors: Hearn, Richard H., Ong, Raymond Y.
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): SRIVASTAVA, VIRENDRA KUMAR
• Application Number:
  US09/187,268
• Time in Patent Office: 767 Days
• Field of Search: 128/204.21, 128/204.23, 128/200.14, 128/204.18
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0027 pressure meter

Abstract

An improved software control system for a positive pressure ventilator that implements the controller that regulates the ventilator solenoid as a finite state machine. The use of a state machine implementation provides multiple degrees of freedom to the designer and provides for a modular, fail safe design.

Claims

1. A software driven ventilator system comprising:

a ventilator system controlled bv a hardware controller, wherein said ventilator system contains a positive-pressure respirator displacing air controlled by an exhalation solenoid activated by said controller;

said controller implemented as a finite state machine in software;

said software implementing said finite state machine controller has a plurality of states for controlling said ventilator system, comprising;

a first weaning state, the CPAP mode, wherein a patient is allowed to breath naturally, with the controller monitoring the patient'"'"'s breathing, and activating said ventilation system, as a backup to the patient'"'"'s natural breathing, in the event of apnea;

a second Assist/Control state, the AC_-- EX mode, wherein a patient is forced respiratory gas by activation of said exhalation solenoid at a predetermined time cycle; and

,

a third synchronous assist state, the SIMV_-- WDW mode, wherein a patient is forced respiratory gas for inhalation by activation of said exhalation solenoid at a predetermined time cycle, and said controller monitoring the patient for natural breathing.

2. The invention according to claim 1, further comprising a console wherein:

wherein each of said states may be entered into from any other state, by the selective activation of a keypad switch on said console.

3. The invention according to claim 1, further comprising:

a standby state, the STBY mode, from which any other state may be entered;

said software implemented controller in said STBY mode changes into a one of a plurality of other states upon the occurrence of a transition event, said plurality of states comprising the STBY mode, the CPAP mode, the AC_-- EX mode, and the SIMV_-- WDW mode.

4. The invention according to claim 3, further comprising:

a manual breath inspiration state, the MB_-- INSP mode, wherein respiratory gas is forced into said patient for a single time cycle upon the selective activation of a predetermined switch.

5. The invention according to claim 4, wherein:

said software implemented controller in said MB_-- INSP mode changes state to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising;

said MB_-- INSP mode, wherein there is no change of state, upon the occurrence of a transition event indicating an emergency condition with the patient, the EXOFF event;

a second manual inspiration state, the MB_-- MIN_-- EX mode, upon the occurrence of a transition event indicating a lapse of a predetermined time interval, the TDELTA event, wherein from said MB_-- MIN_-- EX mode said state changes to said STBY mode, upon the occurrence of a TDELTA event and upon selective activation of a predetermined switch on said console, and said MB_-- MIN_-- EX mode changes to said CPAP mode, upon the occurrence of a TDELTA event and upon selective activation of a predetermined switch on said console.

6. The invention according to claim 1, wherein said software implemented controller has a state comprising a system off state, the SYS_-- OFF mode, wherein said controller is calibrated in said SYS_-- OFF mode, and wherein said SYS_-- OFF mode can change to said AC_-- EX mode, said STBY mode, said CPAP mode and said SIMV_-- WDW mode upon the selective activation of a predetermined switch on said console.

7. The invention according to claim 1, wherein said software implemented controller in said CPAP mode changes states to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising:

a backup inspiration state, the BK_-- INSP mode, wherein a patient is forced respiratory gas by activation of said exhalation solenoid, upon the occurrence of a transition event indicating the detection of apnea from the patient, the APNEA event;

said SIMV_-- WDW mode, upon the occurrence of a transition event indicating the selective activation of a predetermined switch;

said AC_-- EX mode, upon the occurrence of a transition event indicating the selective activation of a predetermined switch.

8. The invention according to claim 7, further comprising:

a manual breath inspiration state, the MB_-- INSP mode, wherein respiratory gas is forced into a patient for a single time cycle upon the selective activation of a predetermined switch;

said CPAP mode changes to said MB_-- INSP mode upon the occurrence of a transition event indicating selective activation of said predetermined switch.

9. The invention according to claim 7,

wherein said software implemented controller in said BK_-- INSP mode changes states to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising:

said BK_-- INSP mode, so there is no change of state, upon the occurrence of a transition event indicating an emergency condition with the patient, the EXOFF event;

a second inspiration state, the BK_-- MIN_-- EX mode, upon the occurrence of a transition event indicating the lapse of a predetermined time interval, the TDELTA event.

10. The invention according to claim 9,

wherein said software implemented controller in said BK_-- MIN_-- EX mode changes states to another state upon the occurrence of a transition event, comprising a state from which said backup inspiration state, BK_-- INSP, may be repeated, the BK_-- EX mode, upon the occurrence of said TDELTA event;

wherein said BK_-- EX mode changes state to one of a plurality of different states, upon the occurrence of a transition event, comprising;

said AC_-- EX, SIMV_-- WDW, and CPAP modes, upon the occurrence of a transition event indicating activation of a predetermined switch;

said CPAP mode, upon the occurrence of an attempt by the patient to breath naturally, the TRIGGER event.

11. The invention according to claim 10, wherein:

wherein said BK_-- EX mode changes state to one of a plurality of different states, upon the occurrence of a transition event, comprising;

said BK_-- INSP mode, upon either the occurrence of a lapse of a another predetermined time interval, the TCYC event, or the activation of a predetermined switch;

said BK_-- EX mode, so that the state does not change, upon the occurrence of either a update of respiratory cycle time, said update reflected in said time interval TDELTA and TCYC, the NEWMODE event, or the activation of a predetermined switch.

12. The invention according to claim 1, wherein said software implemented controller in said SIMV_-- WDW mode changes states to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising:

a state where said exhalation solenoid is activated to force respiratory gas into a patient upon the detection of the occurrence of an attempt by the patient to breathe, the TRIGGER event, termed the SIMV_-- TRIG_-- INSP mode.

13. The invention according to claim 12, wherein said SIMV_-- TRIG_-- INSP state changes state to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising:

said SIMV_-- TRIG_-- INSP state, for no change in state, upon the occurrence of a transition even indicating an emergency condition with the patient, the EXOFF event;

a subsequent state synchronous assist state, SIMV_-- TRIG_-- MIN_-- EX, upon the occurrence of a lapse of a predetermined time interval, the TDELTA event.

14. The invention according to claim 12, wherein:

said software implemented controller in said SIMV_-- WDW mode changes states to a subsequent state that, upon the lapse of a predetermined time interval, changes state to a another subsequent state, the SIMV_-- TRIG_-- EX mode, upon which said exhalation solenoid is deactivated, and the inspiration cycle is completed;

wherein said SIMV_-- TRIG_-- EX mode may change state to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising;

said SIMV_-- WDW mode, upon the lapse of a predetermined time TCYC;

one of said CPAP mode, STBY mode, and AC_-- EX mode, upon the detection of the activation of a predetermined switch associated with said CPAP, STBY and AC_-- EX modes,

said SIMV_-- TRIG_-- EX mode, for no change of state, upon the detection of an emergency condition in a patient, the SPONEX event, or upon the attempt by the patient to breath naturally, the TRIGGER event, before the lapse of said predetermined time TCYC;

said SIMV_-- TRIG_-- EX mode, for no change of state, upon the detection of the activation of a predetermined switch associated with said SIMV_-- TRIG_-- EX mode; and

said SIMV_-- TRIG_-- EX mode, for no change of state, upon the detection of a new cycle time for the respiratory cycle associated with states SIMV_-- WDW and SIMV_-- TRIG_-- EX, a NEWRATE event.

15. The invention according to claim 1, wherein:

said software implemented controller in said AC_-- EX mode changes states to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising;

a first inspiration state, the AC_-- INSP mode, wherein a patient is forced respiratory gas by activation of said exhalation solenoid, upon the occurrence of at least one transition event comprising the detection of an attempt by a patient to breath naturally, the TRIGGER event, the expiration of a predetermined time, the TCYC event, and upon the occurrence of a transition event indicating the selective activation of a predetermined switch, the MBREATH event.

16. The invention according to claim 15, wherein said software implemented controller changes state from said AC_-- EX state to one of a plurality of different states, upon the occurrence of a transition event, comprising:

said STBY mode, said CPAP mode, said SIMV_-- WDW mode, and a system off state, the SYS_-- OFF mode, wherein said controller is calibrated in, wherein said SYS_-- OFF mode can change to said AC_-- EX mode, said STBY mode, said CPAP mode and said SIMV_-- WDW mode upon the selective activation of a predetermined switch on said console.

17. The invention according to claim 15, wherein:

said software implemented controller in said first inspiration state, the AC_-- INSP mode, changes states, upon the occurrence of a transition event, said states and transition events comprising;

a second inspiration state, the AC_-- MIN_-- EX mode, said exhalation solenoid activated to force air into a patient, upon the occurrence of the lapse of a predetermined time, the TDELTA event;

said first inspiration state, the AC_-- INSP mode, for no change in state, upon the occurrence of upon the occurrence of a transition event indicating an emergency condition with the patient, the EXOFF event.

18. The invention according to claim 17, wherein:

said software implemented controller in said second inspiration state, AC_-- MIN_-- EX mode, changes states to said AC_-- EX mode, and deactivates said respiration solenoid to complete the respiratory cycle.

19. A method of operation of a positive-pressure respirator ventilator system containing a exhalation solenoid activated by a controller implemented as a finite state machine comprising the steps of:

implementing said controller as a finite state machine;

providing a change of state to a plurality of states for said finite state machine controller for controlling the operation of said exhalation solenoid.

20. The method of operation according to claim 19, further comprising the steps of:

providing a change of state to a first state, the CPAP mode, wherein a patient is allowed to breath naturally, with the controller monitoring the patient'"'"'s breathing;

activating said ventilation system exhalation solenoid while in said CPAP mode, only in the event of patient apnea, as a backup to said patient'"'"'s natural breathing.

21. The method of operation according to claim 20, further comprising the steps of:

providing a change of state to a second state, the AC_-- EX mode;

activating said exhalation solenoid to force respiratory gas into a patient at a predetermined time cycle when in said AC_-- EX mode.

22. The method of operation according to claim 20, further comprising the steps of:

providing a change of state to a third state, the SIMV_-- WDW mode;

activating said exhalation solenoid to force respiratory gas into a patient at a predetermined time cycle when in said SIMV_-- WDW mode;

monitoring the patient for natural breathing during said SIMV_-- MODE state.

23. The method of operation according to claim 22, further comprising the steps of:

providing a change of state to a fourth state, the STBY mode, from which any of said other states may be entered;

changing states from said STBY mode to said other states upon the occurrence of a transition event.

24. The method of operation according to claim 22, further comprising the steps of:

providing a change of state to a manual breath inspiration state, the MB_-- INSP mode, said MB_-- INSP mode entered into by said controller upon the selective actuation of a predetermined switch;

forcing respiratory gas into said patient for a single time cycle upon the selective activation of said predetermined switch.

25. The method of operation according to claim 22, comprising the steps of:

providing a change of state, when in said CPAP mode, to a plurality of other states for said controller to change to upon the occurrence of a transition event, said steps comprising;

providing a change of state to a backup inspiration state, the BK_-- INSP mode, wherein a patient is forced respiratory gas by activation of said exhalation solenoid, upon the occurrence of a transition event indicating the detection of apnea from the patient, the APNEA event;

providing a change of state to said SIMV_-- WDW mode, said change of state occurring upon the selective activation of a predetermined switch;

providing a change of state to said AC_-- EX mode, said change of state occurring upon the selective activation of a predetermined switch.

26. The method of operation according to claim 25, further comprising the steps of:

providing a change of state to a manual breath inspiration state, the MB_-- INSP mode, wherein respiratory gas is forced into a patient for a single time cycle, upon the selective activation of a predetermined switch;

whereby said CPAP mode changes to said MB_-- INSP mode upon the selective activation of said predetermined switch.

27. The method of operation according to claim 22,

providing a change of state for said controller while in said BK_-- INSP mode, to change states to one of a plurality of other states, upon the occurrence of a transition event, comprising the steps of:

changing to said BK_-- INSP mode, so there is no change of state, upon the occurrence of a transition event indicating an emergency condition with the patient, the EXOFF event;

changing to a second inspiration state, the BK_-- MIN_-- EX mode, upon the occurrence of a transition event indicating the lapse of a predetermined time interval, the TDELTA event.

28. The method of operation according to claim 27, further comprising the steps of:

providing a change of state for said controller in said BK_-- MIN_-- EX mode to change states to another state upon the occurrence of a transition event, comprising a state from which said backup inspiration state, BK_-- INSP, may be repeated, the BK_-- EX mode, upon the occurrence of said TDELTA event;

providing a change of state for said BK_-- EX mode to change state to one of a plurality of different states, upon the occurrence of a transition event, comprising the steps of;

changing to said AC_-- EX, SIMV_-- WDW, and CPAP modes, upon the occurrence of a transition event indicating activation of a predetermined switch;

changing to said CPAP mode, upon the occurrence of an attempt by the patient to breath naturally, the TRIGGER event.

29. The method of operation according to claim 28, wherein:

wherein said BK_-- EX mode changes state to one of a plurality of different states, upon the occurrence of a transition event, comprising;

changing to said BK_-- INSP mode, upon either the occurrence of a lapse of a another predetermined time interval, the TCYC event, or the activation of a predetermined switch;

changing to said BK_-- EX mode, so that the state does not change, upon the occurrence of either a update of respiratory cycle time, said update reflected in said time interval TDELTA and TCYC, the NEWMODE event, or the activation of a predetermined switch.

30. The method of operation according to claim 22, comprising the steps of:

providing a change of state, when in said SIMV_-- WDW mode, to a plurality of different states, upon the occurrence of transition events, comprising;

changing to a state where said exhalation solenoid is activated to force respiratory gas into a patient upon the detection of the occurrence of an attempt by the patient to breathe, the TRIGGER event, termed the SIMV_-- TRIG_-- INSP mode.

31. The method of operation according to claim 30, wherein said SIMV_-- TRIG_-- INSP state changes state to one of a plurality of other states, upon the occurrence of a transition event, comprising the steps of:

changing to said SIMV_-- TRIG_-- INSP state, for no change in state, upon the occurrence of a transition event indicating an emergency condition with the patient, the EXOFF event;

changing to a subsequent state synchronous assist state, SIMV_-- TRIG_-- MIN_-- EX, upon the occurrence of a lapse of a predetermined time interval, the TDELTA event.

32. The method of operation according to claim 30, further comprising the steps of:

providing for a change in state for said software implemented controller in said SIMV_-- WDW mode to a subsequent state that, upon the lapse of a predetermined time interval, changes state to a another subsequent state, the SIMV_-- TRIG_-- EX mode, upon which said exhalation solenoid is deactivated, and the inspiration cycle is completed;

wherein said SIMV_-- TRIG_-- EX mode may change state to one of a plurality of other states, upon the occurrence of a transition event, said states and transition events comprising the steps of;

changing state to said SIMV_-- WDW mode, upon the lapse of a predetermined time TCYC;

changing state to one of said CPAP mode, STBY mode, and AC_-- EX mode, upon the detection of the activation of a predetermined switch associated with said CPAP, STBY and AC_-- EX modes;

changing state to said SIMV_-- TRIG_-- EX mode, for no change of state, upon the detection of an emergency condition in a patient, the SPONEX event, or upon the attempt by the patient to breathe spontaneously, the TRIGGER event, before the lapse of said predetermined time TCYC;

changing state to said SIMV_-- TRIG_-- EX mode, for no change of state, upon the detection of the activation of a predetermined switch associated with said SIMV_-- TRIG_-- EX mode; and

changing state to said SIMV_-- TRIG_-- EX mode, for no change of state, upon the detection of a new cycle time for the respiratory cycle associated with states SIMV_-- WDW and SIMV_-- TRIG_-- EX, a NEWRATE transition event.

33. The method of operation according to claim 33, wherein:

said software implemented controller in said AC_-- EX mode changes states to one of a plurality of other states, upon the occurrence of a transition event, comprising the steps of;

changing state to a first inspiration state, the AC_-- INSP mode, wherein a patient is forced respiratory gas by activation of said exhalation solenoid, upon the occurrence of at least one transition event comprising the detection of an attempt by a patient to breathe, the TRIGGER event, the expiration of a predetermined time, the TCYC event, and upon the occurrence of a transition event indicating the selective activation of a predetermined switch, the MBREATH event.

34. The method of operation according to claim 33, wherein said controller changes state from said AC_-- EX state to one of a plurality of different states, upon the occurrence of a transition event, comprising the steps of:

changing state to said STBY mode, said CPAP mode, said SIMV_-- WDW mode, and a system off state, the SYS_-- OFF mode, wherein said controller is calibrated in, wherein said SYS_-- OFF mode can change to said AC_-- EX mode, said STBY mode, said CPAP mode and said SIMV_-- WDW mode upon the selective activation of a predetermined switch on said console.

35. The method of operation according to claim 33, wherein:

said software implemented controller in said first inspiration state, the AC_-- INSP mode, changes states, upon the occurrence of a transition event, comprising the steps of;

changing state to a second inspiration state, the AC_-- MIN_-- EX mode, said exhalation solenoid activated to force air into a patient, upon the occurrence of the lapse of a predetermined time, the TDELTA event;

changing state to said first inspiration state, the AC_-- INSP mode, for no change in state, upon the occurrence of upon the occurrence of a transition event indicating an emergency condition with the patient, the EXOFF event.

36. The method of operation according to claim 35, further comprising the steps of:

said controller in said second inspiration state, AC_-- MIN_-- EX mode, changes states to said AC_-- EX mode, and deactivates said respiration solenoid to complete the respiratory cycle.