Inverse sawtooth pressure wave train purging in medical ventilators

• US 8,528,554 B2
• Filed: 09/03/2009
• Issued: 09/10/2013
• Est. Priority Date: 09/04/2008
• Status: Expired due to Fees

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Jafari, Medhi M., Aviano, Jeffrey K., Grabol, Daniel G., McCoy, Edward R., Upham, Gail F.
• Primary Examiner(s): Dixon, Annette
• Application Number:
  US12/553,568
• Publication Number:
  US 20100051029A1
• Time in Patent Office: 1,468 Days
• Field of Search: 128/204.23, 128/200.24, 128/204.18, 128/205.23, 128/897, 128/898, 73232-281, 73861-86194, 73 101- 189, 73 232- 3107, 738/615.2
• US Class Current: 128/204.23
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0063 Compressors
• 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 16/085 Gas sampling
• CPC Class Codes: A61M 16/0858 Pressure sampling ports
• CPC Class Codes: A61M 2016/0027 pressure meter

Abstract

This disclosure describes systems and methods for purging narrow diameter sensor tubing, occasionally referred to as “sensor lines,” in a ventilation system. The disclosure describes a novel approach in which a series of short, periodic releases of pressurized gas through the sensor tubes are used to clear any blockages due to condensation or patient secretions.

Claims

1. A method of purging two or more sensor tubes in a medical ventilator providing ventilation to a patient, the method comprising:

a) charging a vessel with gas to a first predetermined pressure;

b) detecting initiation of a first exhalation phase in a breathing cycle of the patient;

c) after step b), releasing gas from the vessel through a first one of the sensor tubes into a patient circuit of the ventilator for a first predetermined period of time;

d) after step c), recharging the vessel with gas to a second predetermined pressure different from the first predetermined pressure; and

e) after step d), releasing gas from the vessel through a second one of the sensor tubes into the patient circuit of the ventilator for a second predetermined period of time.

2. The method of claim 1 further comprising:

f) after step e), repeating step d);

g) after step f), repeating steps c), d) and e).

3. The method of claim 2 further comprising:

h) after step g), repeating steps f) and g) at least once.

4. The method of claim 3 further comprising:

continuously operating a pump to pump gas into the vessel during steps c), d), e), f), g) and h).

5. The method of claim 3 further comprising:

performing steps f) and g) during a subsequent exhalation phase after the first exhalation phase in the breathing cycle of the patient.

6. The method of claim 2 further comprising:

performing step e) during a subsequent exhalation phase after the first exhalation phase in the breathing cycle of the patient.

7. The method of claim 2 further comprising:

performing steps f) and g) during a subsequent exhalation phase after the first exhalation phase in the breathing cycle of the patient.

8. The method of claim 1 wherein charging the vessel further comprises:

engaging a pump to pump the gas into the vessel until the first predetermined pressure is obtained.

9. The method of claim 1 further comprising:

continuously operating a pump to pump gas into the vessel during steps c), d) and e).

10. The method of claim 9 wherein step d), recharging the vessel, further comprises:

waiting for a third predetermined period of time between an end of step c), releasing the gas through the first one of the sensor tubes, and an initiation of step e), thereby allowing the pump to recharge the vessel with gas during the third predetermined period of time.

11. The method of claim 1 wherein the first predetermined period of time and the second predetermined period of time are equal.

12. The method of claim 1 wherein step a) is performed prior to step b).

13. The method of claim 1 wherein each of the first predetermined period of time and the second predetermined period of time are less than about 100 milliseconds.

14. The method of claim 1 wherein each of the first predetermined period of time and the second predetermined period of time are less than about 50 milliseconds.

15. The method of claim 1 wherein each of the first predetermined period of time and the second predetermined period of time are less than about 25 milliseconds.

16. The method of claim 1 wherein each of the first predetermined period of time and the second predetermined period of time are less than about 10 milliseconds.

17. The method of claim 1, further comprising:

detecting an end of the first exhalation phase in the breathing cycle of the patient prior to the performance of step e);

performing step e) during a subsequent exhalation phase after the first exhalation phase in the breathing cycle of the patient.

18. A method of purging a sensor tube connecting a patient circuit of a medical ventilator to a sensor, the method comprising:

repeatedly discharging gas through a first sensor tube into the patient circuit, wherein each gas discharge has a fixed duration of less than 100 milliseconds and each gas discharge is separated from a prior gas discharge by about 200 milliseconds.

19. The method of claim 18 further comprising:

pneumatically disconnecting a sensor associated with the first sensor tube during each gas discharge.

20. The method of claim 18 further comprising:

disabling the sensor associated with the first sensor tube during each gas discharge.

21. The method of claim 18 further comprising:

repeatedly and alternately discharging gas into the patient circuit through the first sensor tube and a second sensor tube.

22. The method of claim 18 wherein each discharging operation further comprises:

opening a valve connecting the first sensor tube to a pressurized vessel for the fixed duration of time.

23. The method of claim 22 further comprising:

repeatedly discharging gas at a decreasing pressure.

24. The method of claim 22 further comprising:

monitoring pressure in the pressurized vessel during the discharging operation.

25. The method of claim 18 further comprising:

monitoring a breathing cycle of a patient connected to the medical ventilator; and

discharging gas only during a specified phase of the breathing cycle.

26. The method of claim 25 further comprising:

discharging gas only during an exhalation phase of the breathing cycle.

27. The method of claim 25 further comprising:

discharging gas during multiple consecutive specified phases of the breathing cycle.

28. The method of claim 18 further comprising:

receiving a user input selecting the fixed duration of each gas discharge.

29. The method of claim 18 further comprising:

determining an amount of gas discharged during at least one gas discharge;

including the amount of gas discharged in a determination of gas flow in the patient circuit.

30. A pressure support system comprising:

a pressure generating system adapted to generate a flow of breathing gas;

a ventilation system including a patient circuit;

at least one circuit sensor in fluid communication with the patient circuit via one or more sensor tubes; and

a sensor tube purge module adapted to initiate a purge cycle that purges the sensor tubes, wherein each purge cycle includes repeatedly discharging gas through the sensor tubes into the patient circuit, wherein each gas discharge has a fixed duration of less than 100 milliseconds and each gas discharge is separated from a prior gas discharge by about 100 milliseconds.

31. The system of claim 30 wherein the ventilation system monitors a patient'"'"'s breathing cycle and the sensor tube purge module discharges gas through a sensor tube only during a predetermined phase of the patient'"'"'s breathing cycle as determined by the ventilation system.

32. The system of claim 30 wherein the sensor tube purge module further comprises:

a pressure vessel from which the gas discharged through the sensor tubes is obtained.

33. The system of claim 32 wherein the sensor tube purge module further comprises:

at least one valve that controls a flow of gas from the pressure vessel through one or more of the sensor tubes.

34. The system of claim 32 wherein the sensor tube purge module further comprises:

at least one vessel sensor that monitors a pressure in or a flow of gas from a pressurized vessel; and

wherein the sensor tube purge module determines a volume of gas discharged through at least one sensor tube into the patient circuit based on data obtained from the at least one vessel sensor.

35. The system of claim 32 wherein the sensor tube purge module further comprises:

a pump that delivers pressurized gas to a pressurized vessel.

36. The system of claim 30 wherein the sensor tube purge module further comprises:

at least one sensor interface valve that disconnects the at least one circuit sensor from its associated sensor tube when gas is discharged through the associated sensor tube.

37. The system of claim 30 wherein the sensor tube purge module further comprises:

at least one regulator that controls flow of gas from a pressurized gas source through the sensor tubes.

38. The system of claim 37 wherein the pressurized gas source is the pressure generating system.

39. The system of claim 30 wherein the sensor tube purge module discharges gas through only one sensor tube at a time.

40. The system of claim 30 wherein the sensor tube purge module simultaneously discharges gas through at least two sensor tubes at a time.

41. A controller for a medical ventilator comprising:

a microprocessor; and

a sensor tube purge module adapted to initiate a purge cycle that purges sensor tubes connected to sensors in the medical ventilator;

wherein each purge cycle includes repeatedly discharging gas through the sensor tubes into a patient circuit, wherein each gas discharge has a fixed duration of less than 100 milliseconds and each gas discharge is separated from a prior gas discharge by about 150 milliseconds.

42. A computer-readable medium having computer-executable instructions for performing a method of purging a sensor tube connecting a patient circuit of a medical ventilator to a sensor, the method comprising:

repeatedly discharging gas through a first sensor tube into the patient circuit, wherein each gas discharge has a fixed duration of less than 100 milliseconds and each gas discharge is separated from a prior gas discharge by about 50 milliseconds.

43. The computer-readable medium of claim 42 wherein the method further comprises:

disconnecting the sensor associated with the first sensor tube during each gas discharge.

44. The computer-readable medium of claim 42 wherein the method further comprises:

repeatedly and alternately discharging gas into the patient circuit through the first sensor tube and a second sensor tube.

45. The computer-readable medium of claim 42 wherein each discharging operation further comprises:

opening a valve connecting the first sensor tube to a pressurized vessel for the fixed duration of time.

46. The computer-readable medium of claim 42 wherein each discharging operation further comprises:

monitoring a breathing cycle of a patient connected to the medical ventilator; and

discharging gas only during a specified phase of the breathing cycle.

47. The computer-readable medium of claim 42 wherein each discharging operation further comprises:

determining an amount of gas discharged during at least one gas discharge;

including the amount of gas discharged in a determination of gas flow in the patient circuit.

48. A medical ventilator system, comprising:

a processor;

a gas regulator in communication with the processor, the gas regulator adapted to regulate a flow of gas from a gas supply to a patient via a patient circuit;

a flow sensor package disposed in the patient circuit, the flow sensor package in communication with a gas accumulator; and

a pressure sensor coupled to the gas accumulator and in communication with the processor, the pressure sensor adapted to provide pressure readings in the gas accumulator to the processor,

wherein the processor is adapted to instruct the accumulator to deliver a desired amount of gas to a first line used to sense differential pressure within a flow sensor disposed in the flow sensor package when the gas accumulator reaches a first predetermined pressure based on the pressure readings provided by the pressure sensor, and

wherein after the delivery of the desired amount of gas to the first line, the processor is adapted to instruct the accumulator to deliver the desired amount of gas to a second line used to sense the differential pressure within the flow sensor disposed in the flow sensor package when the gas accumulator reaches a second predetermined pressure different from the first predetermined pressure based on the pressure readings provided by the pressure sensor.

49. The system as in claim 48, wherein the gas accumulator is adapted to hold the desired amount of gas for delivery to at least one line used to sense the differential pressure within the flow sensor package.

50. The system as in claim 49 wherein the processor is adapted to determine an initiation of a patient exhalation, and to thereafter provide a purge signal to the gas accumulator.

51. The system as in claim 48 wherein the pressure sensor is disposed remote from the flow sensor package.