Patient circuit disconnect system for a ventilator and method of detecting patient circuit disconnect

• US 20060086357A1
• Filed: 10/25/2004
• Published: 04/27/2006
• Est. Priority Date: 10/25/2004
• Status: Active Grant

• Current Assignee: Bird Products Corporation (Becton Dickinson & Co)
• Original Assignee: Bird Products Corporation (Becton Dickinson & Co)
• Inventors: Soliman, Ihab S., Brightup, Vern
• Granted Patent: US 7,984,712 B2
• Time in Patent Office: Days
• US Class Current: 128/204.220
• 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 16/0833 T- or Y-type connectors, e.g. Y-piece
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2016/0042 in the expiratory circuit

Abstract

A method of detecting disconnect of a patient circuit of a ventilation system, wherein a circuit disconnect is detected with a first sensitivity and a second sensitivity. The circuit disconnect detected with the first sensitivity is performed by detecting a volume loss for a minimum period of time, detecting a peak pressure loss for at least two consecutive breathing cycles or a minimum period of time, and detecting a pressure loss continuing for a predetermined period of time. The circuit disconnect detected with the second sensitivity is performed by detecting a volume loss for a single breathing cycle, detecting a pressure loss for a single breathing cycle, and detecting an increase of compliance. The first sensitivity is lower than the second sensitivity. Preferably, an alarm is activated when the circuit disconnect is detected with the first sensitivity, and subsystems of the ventilation system is informed of the circuit disconnect that has been detected with the second sensitivity.

Claims

1. A method of detecting disconnect of a patient circuit of a ventilation system, comprising:

a) detecting a volume loss lasting for a first predetermined period of time;

b) detecting a pressure loss lasting for at least two consecutive breaths or for a breath longer than a second predetermined period of time;

c) detecting a pressure loss continuing for a third predetermined period of time;

d) detecting a volume loss for a single breath;

e) detecting a pressure loss for a single breath; and

f) detecting an increase of compliance.

2. The method of claim 1, further comprising a step of activating an alarm when the circuit disconnect is detected in any of steps (a), (b) and (c).

3. The method of claim 1, further comprising a step of informing subsystems of the ventilation system of the circuit disconnect is detected in step (d), (e) or (f).

4. The method of claim 1, wherein the first predetermined period of time is 5 seconds.

5. The method of claim 1, wherein the second predetermined period of time is 5 seconds.

6. The method of claim 1, wherein the third predetermined period of time is 8 seconds.

7. The method of claim 1, wherein the step (a) comprises:

a1) calculating a first volume leakage percentage for a breath;

a2) comparing the volume leakage percentage to a reference percentage only when a baseline pressure setting is unchanged; and

a3) setting a detection output as logic 1 when the volume leakage percentage larger than the reference percentage lasts for the first predetermined period of time.

8. The method of claim 7, further comprising:

a4) setting a detection output as logic 0 when the volume leakage percentage is smaller than the reference percentage or the baseline pressure setting has been changed.

9. The method of claim 8, further comprising:

a5) resetting calculation of the percentage of volume leakage after steps (a3) or (a4).

10. The method of claim 7, wherein the predetermined percentage is 75%.

11. The method of claim 7, wherein the volume percentage leakage is calculated by a ratio of a difference between inspiratory and expiratory gas volumes and the inspiratory gas volume of each breath.

12. The method of claim 11, wherein the inspiratory and expiratory gas volumes are obtained by integrating inspiratory and expiratory flow rates, respectively.

13. The method of claim 1, wherein step (a) initiates at the beginning of the inspiratory phase of the breath.

14. The method of claim 1, wherein step (b) initiates at the beginning of the inspiratory phase of the breath.

15. The method of claim 1, wherein step (b) comprises:

b1) determining a threshold pressure according to a baseline pressure setting;

b2) comparing a peak expiratory pressure to the threshold pressure;

b3) incrementing a consecutive breath pressure loss counter when the peak expiratory pressure is smaller than the threshold pressure;

b4) counting a time interval of a breath during which the peak expiratory pressure is smaller than the threshold pressure;

b5) setting a consecutive-breath pressure loss detection output as logic 1 when the increment of the consecutive breath pressure loss is at least 2 or the time interval is no shorter than the second predetermined period of time.

16. The method of claim 15, wherein step b1) further comprising:

setting the threshold pressure as the baseline pressure setting minus 10 cmH₂O when the baseline pressure is equal to or larger than 20 cmH₂O;

setting the threshold pressure as the baseline pressure setting minus 2 cmH₂O when the baseline pressure setting is no less than 3 cmH₂O; and

setting the threshold pressure as 0 when the baseline pressure setting is less than 3 cmH₂

17. The method of claim 15, further comprising a step of resetting a long-term volume calculation and a volume timer when the peak expiratory pressure is greater than the threshold pressure and when a pressure loss has been detected already.

18. The method of claim 17, further comprising a step of setting the consecutive-pressure loss detection as logic 0 when the long-term volume calculation and timer have been reset.

19. The method of claim 17, further comprising a step of setting the consecutive pressure detection as logic 0 when the peak expiratory pressure is greater than the threshold pressure and no pressure loss has been detected.

20. The method of claim 1, wherein step (c) comprising:

c1) comparing an expiratory pressure to a threshold pressure determined based on a baseline pressure setting;

c2) counting the time that the expiratory pressure being continuously smaller than the threshold pressure when the baseline pressure has not been changed since last breath; and

c3) setting a continuous pressure loss detection output as logic 1 when the time is no shorter than 8 seconds.

21. The method of claim 20, further comprising setting the continuous pressure loss detection output as logic 0 when the expiratory pressure is larger than the threshold pressure setting and/or the baseline pressure setting has been changed since the last breath.

22. The method of claim 1, wherein step (d) comprises:

d1) calculating a volume leakage percentage for a breath;

d2) comparing the volume leakage percentage to a reference percentage only when a baseline pressure setting is unchanged; and

d3) setting a short-term volume loss detection output as logic 1 when the volume leakage percentage is larger than the predetermined percentage.

23. The method of claim 22, further comprising:

d4) resetting calculation of volumes of inspiratory and expiratory gases for a next breathing cycle.

24. The method of claim 22, wherein the predetermined percentage is 75%.

25. The method of claim 22, wherein the volume percentage leakage is calculated by a ratio of a difference between inspiratory and expiratory gas volumes and the inspiratory volume of each breathing cycle.

26. The method of claim 22, wherein the inspiratory and expiratory gas volumes are obtained by integrating inspiratory and expiratory flow rates, respectively.

27. The method of claim 22, further comprising a step setting the short-term volume loss detection output as logic 0 when the baseline pressure setting has changed and/or the first volume leakage percentage is less than the predetermined percentage.

28. The method of claim 1, wherein step (d) initiates at the beginning of the inspiratory phase of each breath.

29. The method of claim 1, wherein step (e) comprises:

e1) comparing a peak expiratory pressure to a threshold pressure determined according to a baseline pressure setting;

e2) setting a single-breath pressure loss detection output as logic 0 when the expiratory peak pressure is no less than the threshold pressure; and

e3) setting the single-breath pressure loss detection output as logic 1 when the expiratory peak pressure is smaller than the threshold pressure.

30. The method of claim 1, wherein the step of detecting a pressure loss for a single breathing cycle starts at the end of each inspiratory phase.

31. The method of claim 1, wherein step (f) comprises:

f1) computing a pressure difference between an expiratory pressure and a positive expiratory end pressure;

f2) computing a compliance for a first and a second inspiratory phases for two consecutive breathing cycles;

f3) computing a baseline pressure error;

f4) comparing the baseline pressure error with a predetermined error and the pressure difference with a reference error;

f5) comparing the compliance for the first and second inspiratory phases; and

f6) declaring a disconnect by compliance increase when;

i) the baseline pressure error is larger than the predetermined error;

ii) the pressure difference is no less than the predetermined value;

iii) the compliance for the first inspiratory phase is larger than a first predetermined compliance value; and

iv) the compliance for the second inspiratory phase is larger than 2 times the compliance for the first inspiratory phase.

32. The method of claim 31, wherein the predetermined error is 1 cmH₂O.

33. The method of claim 31, wherein the predetermined value is 2 cmH₂O.

34. The method of claim 31, wherein the first predetermined compliance value is 1 ml/cmH₂O.

35. The method of claim 31, further comprising setting a compliance increase detection output as 1 when the disconnect caused by the compliance increase is declared.

36. The method of claim 31, further comprising declaring a disconnect caused by compliance increase when:

the compliance for the first inspiratory phase is no greater than the first predetermined compliance value and larger than a second predetermined compliance value; and

the compliance for the second inspiratory phase is larger than 3 times the compliance for the first inspiratory phase.

37. The method of claim 36, wherein the first predetermined compliance value is 1 and the second predetermined compliance value is 0.

38. A ventilation system, comprising:

an inspiratory flow sensor operative to measure an inspiratory flow of a patient circuit of the ventilation system;

an expiratory flow sensor operative to measure an expiratory flow of the patient circuit;

a pressure sensor operative to measure an expiratory pressure of the patient circuit;

a first set of processing units comprising;

a long-term volume loss detection unit, operative to detect volume loss lasting for at least a first predetermined period of time;

a consecutive pressure loss detection unit, operative to detect pressure loss lasting for at least two consecutive breathing cycles or a second predetermined period of time;

a continuous pressure loss detection unit, operative to detect pressure loss continuing for at least a third predetermined period of time; and

a second set of processing units comprising;

a short-term volume loss detection unit, operative to detect volume loss for a single breathing cycle;

a single-breath pressure loss detection unit, operative to detect pressure loss for a single breathing cycle; and

a compliance increase detection unit, operative to detect compliance increase caused by circuit disconnect.

39. The system of claim 38, further comprising an alarm activated whenever any of the first set of processing units detects a circuit disconnect.

40. The system of claim 38, wherein the second set of processing units is operative to inform subsystems of the ventilation system of a circuit disconnect detected thereby.

41. The system of claim 38, wherein the first set of processing units detect a circuit disconnect less sensitive than the second set of processing units.

42. A device for detecting a disconnect occurring to a patient circuit of a ventilation system, comprising a first processor for generating a primary output to a main alarm, and a second processor for generating a secondary output to inform onboard subsystems of the ventilation system, wherein the first processor is operative to detect a circuit disconnect with a sensitivity less than that of a circuit disconnected detected by the second processor.

43. The device of claim 42, wherein the first processor comprises:

a first processing unit operative to detect a volume loss lasting for a first minimum period of time;

a second processing unit operative to detect a pressure loss of peak expiratory pressure lasting for at least a second minimum period of time or two consecutive breaths; and

a third processing unit operative to detect a continuous pressure loss lasting for a third minimum period of time.

44. The device of claim 42, wherein the second processor comprises:

a first processing unit operative to detect a volume loss occurring within a single breath;

a second processing unit operative to detect a pressure loss of peak expiratory pressure for a single breath; and

a third processing unit operative to a compliance increase caused by circuit disconnect.

45. A method of detecting a disconnect occurring to a patient circuit of a ventilation system, comprising:

generating an alarm when a disconnect of the patient circuit is detected at the first sensitivity; and

informing at least one subsystem of the ventilation system of a disconnect of the patient circuit detect at a second sensitivity;

wherein

the second sensitivity is higher than the first sensitivity.