Automated control for detection of flow limitation
A respiratory flow limitation detection device, which can include an airway pressure treatment generator, determines a flow limitation measure 506 based one or more shape indices for detecting partial obstruction and a measure of a patient's ventilation or respiratory duty cycle. The shape indices may be based on function(s) that ascertain the likelihood of the presence of M-shaped breathing patterns and/or chair-shaped breathing patterns. The measure of ventilation may be based on analysis of current and prior tidal volumes to detect a less than normal patient ventilation. The duty cycle measure may be a ratio of current and prior measures of inspiratory time to respiratory cycle time to detect an increase in the patient's inspiratory cycle time relative to the respiratory cycle time. A pressure setting based on the flow limitation may then be used to adjust the treatment pressure to ameliorate the patient's detected flow limitation condition.
1. A method of detecting partial obstruction comprising:
in one or more processors of a controller of a flow limitation detection device:
receiving a measure of respiratory flow from a flow sensor;
determining a shape index indicative of a pattern of partial obstruction from the measure of respiratory flow;
determining a ratio of a current ventilation measure to a prior ventilation measure, the current ventilation measure calculated by dividing a total of inspired volume and expired volume of a current breathing cycle by a total of inspiratory time and expiratory time of the current breathing cycle;
deriving a flow limitation measure as a function of the determined shape index and the determined ratio of ventilation measures; and
affecting an output of the flow limitation detection device based on the derived flow limitation measure.
2. The method of claim 1 wherein the output is an indication of a detection of partial obstruction.
3. The method of claim 1 wherein the output is an indication of a quantified degree of partial obstruction.
4. The method of claim 1 wherein the output is an adjustment to a parameter of an operation of an associated respiratory treatment device.
5. The method of claim 1 wherein the pattern of partial obstruction is an M shape flow detection function.
6. The method of claim 5 wherein the prior ventilation measure is a recent medium-term ventilation determined by filtering the measure of respiratory flow with a time constant.
7. The method of claim 6 further comprising in the one or more processors calculating a pressure request as a function of the flow limitation measure.
8. The method of claim 7 wherein a processor increases a prior pressure request value based on (a) the shape index being indicative of a presence of an M shape breath in the respiratory flow and (b) the ratio of ventilation measures decreasing sufficiently to be indicative of less than normal ventilation.
9. The method of claim 8 further comprising in the one or more processors determining a second shape index indicative of a chair pattern of partial obstruction determined from the measure of respiratory flow and wherein the derived flow limitation measure is a further function of the second shape index.
10. A non-transitory information-bearing medium having processor-readable information thereon, the processor-readable information to control a processor for detecting respiratory partial obstruction with a flow limitation detection device, the processor-readable information when executed by a processor, perform at least the following:
receiving a measure of respiratory flow in the processor from a sensor;
determining a shape index indicative of a pattern of partial obstruction from the measure of respiratory flow in the processor;
determining a ratio of a current ventilation measure to a prior ventilation measure in the processor, the current ventilation measure calculated by dividing a total of inspired volume and expired volume of a current breathing cycle by a total of inspiratory time and expiratory time of the current breathing cycle;
deriving a flow limitation measure as a function of the determined shape index and the determined ratio of ventilation measures in the processor; and
affecting an output of the flow limitation detection device based on the derived flow limitation measure.
11. The non-transitory information bearing medium of claim 10 wherein the output is an indication of a detection of partial obstruction.
12. The non-transitory information bearing medium of claim 10 wherein the output is an indication of a quantified degree of partial obstruction.
13. The non-transitory information bearing medium of claim 10 wherein the output is an adjustment to a parameter of an operation of an associated respiratory treatment device.
14. The non-transitory information-bearing medium of claim 10 wherein the pattern of partial obstruction is an M shape flow detection function.
15. The non-transitory information-bearing medium of claim 14 wherein the prior ventilation measure is a recent medium-term ventilation determined by filtering the measure of respiratory flow with a time constant.
16. The non-transitory information-bearing medium of claim 10 wherein the processor-readable information further comprises calculating a pressure request as a function of the flow limitation measure in the processor.
17. The non-transitory information-bearing medium of claim 16 wherein the processor-readable information comprises increasing a prior pressure request value in the processor based on (a) the shape index being indicative of a presence of an M shape breath in respiratory airflow and (b) the ratio of ventilation measures decreasing sufficiently to be indicative of less than normal ventilation.
18. The non-transitory information-bearing medium of claim 10 wherein the processor-readable information further comprises determining in the processor a second shape index indicative of a chair pattern of partial obstruction determined from the measure of respiratory flow and wherein the derived flow limitation measure is a further function of the second shape index.
19. A method of detecting partial obstruction comprising:
in one or more processors of a controller of a flow limitation detection device:
receiving a measure of respiratory flow from a sensor;
determining a shape index indicative of a pattern of partial obstruction from the measure of respiratory flow;
determining a duty cycle measure from the measure of respiratory flow, the determined duty cycle measure being a ratio of a current duty cycle measure to a prior duty cycle measure, the current duty cycle measure being a ratio of inspiration time of a current breathing cycle to a total breath time of the current breathing cycle;
deriving a flow limitation measure as a function of the determined shape index and the determined duty cycle measure; and
affecting an output of the flow limitation detection device based on the derived flow limitation measure.
20. The method of claim 19 wherein the output is an indication of a detection of partial obstruction.
21. The method of claim 19 wherein the output is an indication of a quantified degree of partial obstruction.
22. The method of claim 19 wherein the output is an adjustment to a parameter of an operation of an associated respiratory treatment device.
23. The method of claim 19 wherein the pattern of partial obstruction is an M shape flow detection function.
24. The method of claim 23 wherein the prior duty cycle measure is a recent medium-term duty cycle measure determined by filtering with a time constant.
25. The method of claim 24 further comprising calculating a pressure request as a function of the flow limitation measure.
26. The method of claim 25 wherein a processor increases a prior pressure request value based on the shape index being indicative of a presence of an M shape breath in respiratory airflow and an increase of the duty cycle measure.
27. The method of claim 26 further comprising determining a second shape index indicative of a chair pattern of partial obstruction determined from the measure of respiratory flow and wherein the derived flow limitation measure is a further function of the second shape index.
28. A non-transitory information-bearing medium having processor-readable information thereon, the processor-readable information to control a processor for detecting respiratory partial obstruction with a flow limitation detection device, the processor-readable information when executed by a processor, perform at least the following:
accessing in the processor a measure of respiratory flow;
determining in the processor a shape index indicative of a pattern of partial obstruction from the measure of respiratory flow;
determining in the processor a duty cycle measure from the measure of respiratory flow, the determined duty cycle measure being a ratio of a current duty cycle measure to a prior duty cycle measure, the current duty cycle measure being a ratio of inspiration time of a current breathing cycle to a total breath time of the current breathing cycle;
deriving in the processor a flow limitation measure as a function of the determined shape index and the determined duty cycle measure; and
affecting an output of the flow limitation detection device based on the derived flow limitation measure.
29. The non-transitory information bearing medium of claim 28 wherein the output is an indication of a detection of partial obstruction.
30. The non-transitory information bearing medium of claim 28 wherein the output is an indication of a quantified degree of partial obstruction.
31. The non-transitory information bearing medium of claim 28 wherein the output is an adjustment to a parameter of an operation of an associated respiratory treatment device.
32. The non-transitory information-bearing medium of claim 28 wherein the pattern of partial obstruction is an M shape flow detection function.
33. The non-transitory information-bearing medium of claim 32 wherein the prior duty cycle measure is a recent medium-term duty cycle measure determined by filtering with a time constant.
34. The non-transitory information-bearing medium of claim 28 wherein the processor-readable information further comprises calculating a pressure request as a function of the flow limitation measure.
35. The non-transitory information-bearing medium of claim 34 wherein the calculating increases a prior pressure request value based on the shape index being indicative of a presence of an M shape breath in respiratory airflow and an increase of the duty cycle measure.
36. The non-transitory information-bearing medium of claim 28 wherein the processor-readable information further comprises determining a second shape index indicative of a chair pattern of partial obstruction determined from the measure of respiratory flow and wherein the derived flow limitation measure is a further function of the second shape index.
37. A method of determining a treatment setting for a respiratory treatment device comprising:
in one or more processors of a controller of a respiratory treatment device:
accessing a measure of respiratory flow;
from the measure of respiratory flow, determining a shape index representing a degree of partial obstruction;
from the measure of respiratory flow, determining a ratio of ventilation measures representing a degree of change in ventilation, the ratio of ventilation measures being a ratio of a current ventilation measure to a prior ventilation measure, the current ventilation measure calculated by dividing a total of inspired volume and expired volume of a current breathing cycle by a total of inspiratory time and expiratory time of the current breathing cycle;
calculating a treatment setting for the controller of the respiratory treatment device as a proportional function of both the degree of partial obstruction and the degree of change in ventilation; and
setting the controller of the respiratory treatment device to control a treatment with the calculated treatment setting.
38. The method of claim 37 wherein the shape index is determined from a number of breaths in a range from 1 to 3 breaths.
39. The method of claim 37 wherein the shape index is an M-shape breath index.
40. The method of claim 37 wherein the treatment setting is applied by the controller to set an auto-titrating respiratory treatment device.