METHODS AND SYSTEMS FOR BREATH DELIVERY SYNCHRONIZATION

• US 20160045694A1
• Filed: 08/15/2014
• Published: 02/18/2016
• Est. Priority Date: 08/15/2014
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Esmaeil-zadeh-azar, Farhad
• Granted Patent: US 9,808,591 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/4538 Evaluating a particular part of the muscoloskeletal system or a particular medical condition
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7289 Retrospective gating, i.e. associating measured signals or images with a physiological event after the actual measurement or image acquisition, e.g. by simultaneously recording an additional physiological signal during the measurement or image acquisition
• 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 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2016/0042 in the expiratory circuit
• CPC Class Codes: A61M 2205/3303 Using a biosensor
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2230/40 Respiratory characteristics

Abstract

Systems and methods for triggering inspiration and/or cycling exhalation with a ventilator are described herein. In particular, systems and methods for synchronizing ventilator breath delivery with patient breath demand utilizing a digital sample counting trigger mode are described herein. The digital sample counting triggering mode characterizes digital samples taken from a measured or estimated parameter during the patient inhalation/exhalation period to synchronize breath delivery with patient breath demand.

Claims

1. A method for ventilating a patient with a ventilator, comprising:

monitoring a physiological parameter of the patient based on one or more received sensor measurements;

calculating a first derivative and a second derivative of the physiological parameter for a first sample period;

selecting a first trigger count threshold and a first level based on the second derivative;

updating a sample count to form a first updated sample count for the first sample period based on first comparison results from at least one of the following;

comparing the first trigger count threshold to a previous trigger count threshold selected in a previous sample period,

comparing the first derivative to a previous first derivative calculated for the previous sample period and comparing the second derivative to a previous second derivative calculated for the previous sample period,

comparing an array of maxima of the second derivative to an array threshold,

comparing the second derivative to the first level, and

comparing a first rate of change for the second derivative to a rate threshold;

comparing the first updated sample count to the first trigger count threshold; and

triggering inspiration based on a first result of the comparing of the first updated sample count to the first trigger count threshold.

2. The method of claim 1, wherein the first result is that the first updated sample count is equal to the first trigger count threshold.

3. The method of claim 1, wherein the comparing of the first updated sample count to the first trigger count threshold has a second result, wherein the second result is that the first updated sample count is not equal to the first trigger count threshold.

4. The method of claim 3, further comprising:

calculating a next first derivative and a next second derivative of the physiological parameter for a second sample period;

selecting a second trigger count threshold and a second level based on the next first derivative and the next second derivative;

updating the first updated sample count to form a second updated sample count for the second sample period based on second comparison results from at least one of the following;

comparing the second trigger count threshold to the first trigger count threshold.

comparing the next first derivative to the first derivative for the first sample period and comparing the next second derivative to the second derivative for the first sample period,

comparing a next array of maxima for the next second derivative to the array threshold,

comparing the second derivative to the second level, and

calculating a second rate of change for the next second derivative and comparing the second rate of change to the rate threshold;

comparing the second updated sample count to the second trigger count threshold;

determining that the second updated sample count is equal to the second trigger count threshold based on the comparison of the second updated sample count to the second trigger count threshold; and

triggering inspiration based on the determining that the second updated sample count is equal to the second trigger count threshold.

5. The method of claim 1, wherein the first derivative and the second derivative are amplified.

6. The method of claim 1, wherein the first trigger count threshold is selected from a count of 2 or 4.

7. The method of claim 1, wherein the first level is selected from one of the following groups:

−

3 cm of H₂O per second and −

8 cm of H₂O per second;

−

4 cm of H₂O per second and −

9 cm of H₂O per second;

−

5 cm of H₂O per second and −

10 cm of H₂O per second;

−

10 cm of H₂O per second and −

15 cm of H₂O per second; and

−

15 cm of H₂O per second and −

20 cm of H₂O per second.

8. The method of claim 1, wherein the selecting the first trigger count threshold and the first level based on the first derivative and the second derivative comprises:

determining a signal to noise ratio of the second derivative; and

comparing the signal to noise ratio of the second derivative to a ratio threshold.

9. The method of claim 8, wherein the selecting the first trigger count threshold and the first level based on the first derivative and the second derivative further comprises:

determining that the signal to noise ratio for the second derivative is greater than the ratio threshold based on the comparing the signal to noise ratio for the second derivative to the ratio threshold; and

selecting a small trigger count threshold for the first trigger count threshold and selecting a large level for the first level based on the determining that the signal to noise ratio for the second derivative is greater than the ratio threshold.

10. The method of claim 9, wherein the selecting the first trigger count threshold and the first level based on the first derivative and the second derivative further comprises:

determining that the signal to noise ratio for the second derivative is less than or equal to the ratio threshold based on the comparing the signal to noise ratio for the second derivative to the ratio threshold; and

selecting a large trigger count threshold for the first trigger count threshold and selecting a small level for the first level based on the determining that the signal to noise ratio for the second derivative is less than or equal to the ratio threshold.

11. The method of claim 1, wherein the updating the sample count for the first sample period further comprises:

determining that the first trigger count threshold is equal to the previous trigger count threshold based on the comparing of the first trigger count threshold to the previous trigger count threshold;

determining that the second derivative is less than the previous second derivative calculated for the previous sample period based on the comparing the second derivative to the previous second derivative calculated for the previous sample period;

determining that the array of the maxima of the second derivative is less than the array threshold based on the comparing of the array of the maxima of the second derivative to the array threshold;

determining that the second derivative is less than or equal to the first level based on the comparing of the second derivative to the first level; and

determining that the first rate of change for the second derivative is less than the rate threshold based on the comparing of the first rate of change to the rate threshold; and

updating a previous sample count by +1 to form the first updated sample count.

12. The method of claim 1, wherein the updating the sample count for the first sample period further comprises at least one of the following:

determining that the first trigger count threshold is not equal to the previous trigger count threshold based on the comparing of the first trigger count threshold to the previous trigger count threshold,

determining that the second derivative is equal to or more than the previous second derivative based on the comparing of the first derivative to the previous first derivative and the comparing of the second derivative to the previous second derivative,

determining that the array of the maxima of the second derivative is more than or equal to the array threshold based on the comparing of the array of the maxima of the second derivative to the array threshold;

determining that the second derivative is more than to the first level based on the comparing of the second derivative to the first level, and

determining that the first rate of change for the second derivative is more than or equal to the rate threshold based on the comparing of the first rate of change to the rate threshold, and

wherein the updating the sample count for the first sample period further comprises setting the first updated sample count to zero.

13. The method of claim 1, wherein the physiological parameter is an estimated patient effort.

14. The method of claim 1, wherein the physiological parameter is one of the following:

a direct measurement of patient effort, a pressure, a flow, a net flow, a rate of change of flow, a rate of change of pressure, an estimated pressure, or an estimated flow.

15. A ventilator system comprising:

a pressure generating system that generates a flow of breathing gas;

one or more sensors operatively coupled to at least one of the pressure generating system, a patient, and a ventilation tubing system that delivers the flow of breathing gas from the pressure generating system to the patient, wherein the one or more sensors generate sensor output for each sample period;

a parameter module that monitors a physiological parameter from the sensor output for each sample period;

a derivative module that calculate a first derivative and a second derivative for the physiological parameter for each sample period;

a threshold module that selects a trigger count threshold and a level based on the second derivative for each sample period;

a counter module that updates a sample count based at least on the first derivative, the second derivative, the level, and the trigger count threshold for each sample period to form an updated sample count;

a compare module that compares a selected trigger count threshold to the updated sample count for a same sample period; and

a trigger module that triggers inspiration based on a receipt of a first result from the compare module.

16. The ventilator system of claim 15, wherein the counter module determines that the trigger count threshold is equal to a previous trigger count threshold,

wherein the counter module determines that the first derivative is less than a previous first derivative,

wherein the counter module determines that the second derivative is less than a previous second derivative,

wherein the counter module determines that an array of maxima of the second derivative is less than an array threshold,

wherein the counter module determines that the second derivative is less than or equal to the level,

wherein the counter module determines that a first rate of change for the second derivative is less than a rate threshold,

wherein the counter module updates the sample count by 1 to form the updated sample count,

wherein the compare module determines that the updated sample count is equal to the selected trigger count threshold for the same sample period, and

wherein the compare module sends the first result to the trigger module based on a determination that the updated sample count is equal to the selected trigger count threshold for the same sample period.

17. The ventilator system of claim 15, wherein the counter module determines at least one of the following comparison results:

the trigger count threshold is not equal to a previous trigger count threshold,

the first derivative is equal to or more than a previous first derivative,

the second derivative is equal to or more than a previous second derivative,

an array of maxima of the second derivative is more than or equal to an array threshold,

the second derivative is more than the level, and

a first rate of change for the second derivative is more than or equal to a rate threshold, and

wherein the counter module updates the sample count to zero to form the updated sample count,

wherein the compare module determines that the updated sample count is not equal to the selected trigger count threshold for the same sample period,

wherein the compare module sends a second result to the trigger module based on a determination that the updated sample count is not equal to the selected trigger count threshold for the same sample period, and

wherein the trigger module does not trigger inspiration based on a receipt of the second result from the compare module.

18. The ventilator system of claim 15, wherein the physiological parameter is an estimated patient effort.

19. The ventilator system of claim 15, wherein the threshold module determines a signal to noise ratio for the second derivative for each sample period and compares the signal to noise ratio to a ratio threshold to select the trigger count threshold and the level for each sample period.

20. A computer-readable medium having computer-executable instructions for performing a method of ventilating a patient with a ventilator, the instructions comprising:

monitor an estimated patient effort of the patient based on received sensor measurements;

calculate a first derivative and a second derivative of the estimated patient effort for a first sample period;

select a first trigger count threshold and a first level based on the first derivative and the second derivative;

update a sample count to form a first updated sample count for the first sample period based on a comparison result from comparing the second derivative to the first level;

compare the first updated sample count to the first trigger count threshold; and

trigger inspiration based on a first result from the comparing of the first updated sample count to the first trigger count threshold.